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Papers on anthropogenic global warming and next glaciation

Posted by Ari Jokimäki on February 18, 2014

This is a list of papers on anthropogenic global warming and next glaciation. List also contains some papers that discuss next glaciation more generally. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

Impact of anthropogenic CO2 on the next glacial cycle – Herrero et al. (2013) “The model of Paillard and Parrenin (Earth Planet Sci Lett 227(3–4):263–271, 2004) has been recently optimized for the last eight glacial cycles, leading to two different relaxation models with model-data correlations between 0.8 and 0.9 (García-Olivares and Herrero (Clim Dyn 1–25, 2012b)). These two models are here used to predict the effect of an anthropogenic CO2 pulse on the evolution of atmospheric CO2, global ice volume and Antarctic ice cover during the next 300 kyr. The initial atmospheric CO2 condition is obtained after a critical data analysis that sets 1300 Gt as the most realistic carbon Ultimate Recoverable Resources (URR), with the help of a global compartmental model to determine the carbon transfer function to the atmosphere. The next 20 kyr will have an abnormally high greenhouse effect which, according to the CO2 values, will lengthen the present interglacial by some 25 to 33 kyr. This is because the perturbation of the current interglacial will lead to a delay in the future advance of the ice sheet on the Antarctic shelf, causing that the relative maximum of boreal insolation found 65 kyr after present (AP) will not affect the developing glaciation. Instead, it will be the following insolation peak, about 110 kyr AP, which will find an appropriate climatic state to trigger the next deglaciation.” Carmen Herrero, Antonio García-Olivares, Josep L. Pelegrí, Climatic Change, December 2013, DOI: 10.1007/s10584-013-1012-0.

Determining the natural length of the current interglacial – Tzedakis et al. (2012) “No glacial inception is projected to occur at the current atmospheric CO2 concentrations of 390 ppmv (ref. 1). Indeed, model experiments suggest that in the current orbital configuration—which is characterized by a weak minimum in summer insolation—glacial inception would require CO2 concentrations below preindustrial levels of 280 ppmv (refs 2, 3, 4). However, the precise CO2 threshold4, 5, 6 as well as the timing of the hypothetical next glaciation7 remain unclear. Past interglacials can be used to draw analogies with the present, provided their duration is known. Here we propose that the minimum age of a glacial inception is constrained by the onset of bipolar-seesaw climate variability, which requires ice-sheets large enough to produce iceberg discharges that disrupt the ocean circulation. We identify the bipolar seesaw in ice-core and North Atlantic marine records by the appearance of a distinct phasing of interhemispheric climate and hydrographic changes and ice-rafted debris. The glacial inception during Marine Isotope sub-Stage 19c, a close analogue for the present interglacial, occurred near the summer insolation minimum, suggesting that the interglacial was not prolonged by subdued radiative forcing7. Assuming that ice growth mainly responds to insolation and CO2 forcing, this analogy suggests that the end of the current interglacial would occur within the next 1500 years, if atmospheric CO2 concentrations did not exceed 240±5 ppmv.” P. C. Tzedakis, J. E. T. Channell, D. A. Hodell, H. F. Kleiven & L. C. Skinner, Nature Geoscience 5, 138–141(2012), doi:10.1038/ngeo1358. [Full text]

How can a glacial inception be predicted? – Crucifix (2011) “The Early Anthropogenic Hypothesis considers that greenhouse gas concentrations should have declined during the Holocene in absence of humankind activity, leading to glacial inception around the present. It partly relies on the fact that present levels of northern summer incoming solar radiation are close to those that, in the past, preceded a glacial inception phenomenon, associated with declines in greenhouse gas concentrations. However, experiments with various numerical models of glacial cycles show that next glacial inception may still be delayed by several tens of thousands of years, even with the assumption of a decline in greenhouse gas concentrations during the Holocene. Furthermore, as we show here, conceptual models designed to capture the gross dynamics of the climate system as a whole suggest also that small disturbances may sometimes cause substantial delays in glacial events, causing a fair level of unpredictability on ice age dynamics. This suggests the need for a validated mathematical description of climate system dynamics that allows us to quantify uncertainties on predictions. Here, it is proposed to organise our knowledge about the physics and dynamics of glacial cycles through a Bayesian inference network. Constraints on the physics and dynamics of climate can be encapsulated into a stochastic dynamical system. These constraints include, in particular, estimates of the sensitivity of the components of climate to external forcings, inferred from plans of experiments with large simulators of the atmosphere, oceans and ice sheets. On the other hand, palaeoclimate observations are accounted for through a process of parameter calibration. We discuss promises and challenges raised by this programme.” Michel Crucifix, The Holocene August 2011 vol. 21 no. 5 831-842, doi: 10.1177/0959683610394883. [Full text]

The impact of insolation, greenhouse gas forcing and ocean circulation changes on glacial inception – Vettoretti & Peltier (2011) “In this study we employ the NCAR CCSM3 coupled model to investigate the onset of high northern latitude perennial snow cover. Two periods of Earth’s insolation history, that of the pre-industrial period and that of 116 ka before present (BP), are used as benchmarks in an investigation of the influences of interglacial greenhouse gas (GHG) concentration and insolation upon the occurrence of permanent summer snow cover. An additional two experiments at 10 ka and 51 ka into the future (AP) using a typical interglacial GHG level are used to investigate the length of the current interglacial. Results from this set of multicentury sensitivity experiments demonstrate the relative importance of forcings due to insolation and atmospheric greenhouse gases at the millennial scale, and of Atlantic ocean overturning strength (AMOC) at the century scale. We find that while areas of perennial snow cover are sensitive to GHG concentrations, they are much more sensitive to the contemporaneous insolation regime. The goodness of fit of the climatology of the control model to the modern observed climatology is found to influence the modeling results. While there is a strong correlation between AMOC decadal variability and high latitude surface temperature in our control climates, we find little change in AMOC strength during our simulations of 116 ka BP climate nor do we find significant correlation between high latitude snow accumulation and the AMOC. Both the 10 ka AP and 51 ka AP future simulations produce inception events which are much stronger than that of the equivalent pre-industrial simulation. The simulation of inception at 10 ka into the future suggests a maximum duration of the current interglacial of approximately 20 ka in the absence of modern anthropogenic forcing.” G. Vettoretti, W.R. Peltier, The Holocene August 2011 vol. 21 no. 5 803-817, doi: 10.1177/0959683610394885.

A movable trigger: Fossil fuel CO2 and the onset of the next glaciation – Archer & Ganopolski (2005) “The initiation of northern hemisphere ice sheets in the last 800 kyr appears to be closely controlled by minima in summer insolation forcing at 65°N. Beginning from an initial typical interglacial pCO2 of 280 ppm, the CLIMBER-2 model initiates an ice sheet in the Northern Hemisphere when insolation drops 0.7 σ (standard deviation) or 15 W/m2 below the mean. This same value is required to explain the history of climate using an orbitally driven conceptual model based on insolation and ice volume thresholds (Paillard, 1998). When the initial baseline pCO2 is raised in CLIMBER-2, a deeper minimum in summertime insolation is required to nucleate an ice sheet. Carbon cycle models indicate that ∼25% of CO2 from fossil fuel combustion will remain in the atmosphere for thousands of years, and ∼7% will remain beyond one hundred thousand years (Archer, 2005). We predict that a carbon release from fossil fuels or methane hydrate deposits of 5000 Gton C could prevent glaciation for the next 500,000 years, until after not one but two 400 kyr cycle eccentricity minima. The duration and intensity of the projected interglacial period are longer than have been seen in the last 2.6 million years.” David Archer, Andrey Ganopolski, Geochemistry, Geophysics, Geosystems, Volume 6, Issue 5, May 2005, DOI: 10.1029/2004GC000891. [Full text]

The Earth’s Climate in the Next Hundred Thousand years (100 kyr) – Berger et al. (2003) “One of the most striking features of the Quaternary paleoclimate records remains the so-called 100-kyr cycle which is undoubtedly linked to the future of our climate. Such a 100-kyr cycle is indeed characterised by long glacial periods followed by a short-interglacial (∼10–15 kyr long). As we are now in an interglacial, the Holocene, the previous one (the Eemian, which corresponds quite well to Marine Isotope Stage 5e, peaking at ∼125 kyr before present, BP) was assumed to be a good analogue for our present-day climate. In addition, as the Holocene is 10 kyr long, paleoclimatologists were naturally inclined to predict that we are quite close to the next ice age. Simulations using the 2-D climate model of Louvain-la-Neuve show, however, that the current interglacial will most probably last much longer than any previous ones. It is suggested here that this is related to the shape of the Earth’s orbit around the Sun, which will be almost circular over the next tens of thousands of years. As this is primarily related to the 400-kyr cycle of eccentricity, the best and closest analogue for such a forcing is definitely Marine Isotopic Stage 11 (MIS-11), some 400 kyr ago, not MIS-5e. Because the CO2 concentration in the atmosphere also plays an important role in shaping long-term climatic variations – especially its phase with respect to insolation – a detailed reconstruction of this previous interglacial from deep sea and ice records is urgently needed. Such a study is particularly important in the context of the already exceptional present-day CO2 concentrations (unprecedented over the past million years) and, even more so, because of even larger values predicted to occur during the 21st century due to human activities.” A. Berger, M. F. Loutre, M. Crucifix, Surveys in Geophysics, March 2003, Volume 24, Issue 2, pp 117-138. [Full text]

An Exceptionally Long Interglacial Ahead? – Berger & Loutre (2002) “Today’s comparatively warm climate has been the exception more than the rule during the last 500,000 years or more. If recent warm periods (or interglacials) are a guide, then we may soon slip into another glacial period. But Berger and Loutre argue in their Perspective that with or without human perturbations, the current warm climate may last another 50,000 years. The reason is a minimum in the eccentricity of Earth’s orbit around the Sun.” A. Berger, M. F. Loutre, Science 23 August 2002: Vol. 297 no. 5585 pp. 1287-1288, DOI: 10.1126/science.1076120. [Full text]

Future Climatic Changes: Are We Entering an Exceptionally Long Interglacial? – Loutre & Berger (2000) “Various experiments have been conducted using the Louvain-la-Neuve two-dimensional Northern Hemisphere climate model (LLN 2-D NH) to simulate climate for the next 130 kyr into the future. Simulations start with values representing the present-day Northern Hemisphere ice sheet, using different scenarios for future CO2 concentrations. The sensitivity of the model to the initial size of the Greenland ice sheet, and to possible impacts of human activities, has also been tested. Most of the natural scenarios indicate that: (i) the climate is likely to experience a longlasting (∼50 kyr) interglacial; (ii) the next glacial maximum is expected to be most intense at around 100 kyr after present (AP), with a likely interstadial at ∼60 kyr AP; and (iii) after 100 kyr AP continental ice rapidly melts, leading to an ice volume minimum 20 kyr later. However, the amplitude and, to a lesser extent, the timing of future climatic changes depend on the CO2 scenario and on the initial conditions related to the assumed present-day ice volume. According to our modelling experiments, man’s activities over the next centuries may significantly affect the ice-sheet’s behaviour for approximately the next 50 kyr. Finally, the existence of thresholds in CO2 and insolation, earlier shown to be significant for the past, is confirmed to be also important for the future.” M. F. Loutre, A. Berger, Climatic Change, July 2000, Volume 46, Issue 1-2, pp 61-90, DOI 10.1023/A:1005559827189. [Full text]

The end of the present interglacial: how and when? – Broecker (1998) “Despite the large decline in Northern Hemisphere summer insolation during the last 8000 years, neither sea level nor polar temperatures have as yet undergone any significant downturn. This behavior is consistent with the prediction by Kukla and Matthews (1972) that the Holocene interglacial will terminate suddenly with a jump to another of the climate system’s modes of operation. This is what happened at the end of the last period of peak interglaciation. However, complicating the situation is evidence that ice sheet growth during the transition from marine stage 5e to 5d preceded the shut down of the Atlantic’s conveyor circulation which is thought to have brought Europe’s Eemian to a close. If so, then in the natural course of events, the end of the present interglaciation awaits the onset of icecap growth. However, it must be kept in mind that the ongoing buildup of greenhouse gases may alter the natural course of events. In particular, the warming and wetting of the planet will gradually reduce the density of surface waters in the regions where deep waters form. As this reduction is not likely to be symmetrical between the northern Atlantic and the margin of the Antarctic continent, the current near balance between deep water production in the north and south may be disrupted causing an abrupt reorganization of the ocean’s thermohaline circulation. Based on the paleoclimatic record, such a reorganization would have had a profound impact on the planet’s climate.” Broecker, W.S., Quaternary Science Reviews, Volume 17, Number 8, 1 August 1998 , pp. 689-694(6), DOI: [Full text]

Summer solstice solar radiation, the 100 kyr Ice Age cycle, and the next Ice Age – Ledley (1995) “Modeling studies suggest that the summer solstice solar radiation is more important than the caloric half-year solar radiation in producing glacial/interglacial cycles because it is more representative of the energy available to melt ice during the short melt season. Here it is shown that the correlation between the summer solstice solar radiation and the rate of change of the oxygen isotope record is generally greater than that between the caloric half-year radiation and the rate of change of the oxygen isotope record. These results also suggest that the sawtoothed nature of the 100 kyr cycle may be produced by periods of relatively slow changes in ice volume, punctuated by periods of rapid growth that are initiated at times of extremely low summer solstice radiation; and that it is unlikely that an ice age will begin in the next 70 kyr.” Tamara Shapiro Ledley, Geophysical Research Letters, Volume 22, Issue 20, pages 2745–2748, 15 October 1995, DOI: 10.1029/95GL03027.

Possible effects of anthropogenically-increased CO2 on the dynamics of climate: Implications for ice age cycles – Saltzman et al. (1993) “A dynamical model, developed to account for the observed major variations of global ice mass and atmospheric CO2 during the late Cenozoic, is used to provide a quantitative demonstration of the possibility that the anthropogenically-forced increase of atmospheric CO2, if maintained over a long period of time (perhaps by tectonic forcing), could displace the climatic system from an unstable regime of oscillating ice ages into a more stable regime representative of the pre-Pleistocene. This stable regime is characterized by orbitally-forced oscillations that are of much weaker amplitude than prevailed during the Pleistocene.” Barry Saltzman, Kirk A. Maasch, Mikhail Ya. Verbitsky, Geophysical Research Letters, Volume 20, Issue 11, pages 1051–1054, 7 June 1993, DOI: 10.1029/93GL01015.

Quaternary Research special issue: The end of the present interglacial – several authors, 24 papers (1972) Only abstracts are available for individual papers. Quaternary Research, Volume 2, Issue 3, Pages 261-445 (November 1972).

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Papers on health effects of increased CO2

Posted by Ari Jokimäki on November 4, 2011

This is a list of papers dealing with different aspects of the health effects of increased carbon dioxide. The list contains subsections for general studies, increasing atmospheric CO2 and allergies, and extreme carbon dioxide events. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (April 11, 2013): New section for atmospheric carbon dioxide and allergies added including 10 papers.
UPDATE (November 9, 2011): Robertson (2006) added.

General studies

High carbon dioxide concentrations in the classroom: the need for research on the effects of children’s exposure to poor indoor air quality at school – Miller et al. (2010) “Air quality and its effect on health have received recent attention from the House of Commons Environmental Audit Committee. 1 While outdoor air pollution is clearly important and contributes to indoor air quality, indoor air pollution sources and the time spent in indoor environments are key to understanding exposure.” Janice Miller, Sean Semple, Stephen Turner, Occup Environ Med 2010;67:799 doi:10.1136/oem.2010.057471.

Occupational hazards of carbon dioxide exposure – Scott et al. (2009) “This paper is an overview of the occupational hazards that result from exposure to carbon dioxide. It details the main uses, characteristics, and problems that have been identified when carbon dioxide is utilized in various working environments. Carbon dioxide is always a danger when present in enclosed spaces at elevated concentrations. Situations resulting from acute and chronic exposures involving the gaseous and dry ice forms of carbon dioxide are discussed in detail. Current rationale concerning exposure limits and monitoring recommendations are highlighted.” Jonathan L. Scott, David G. Kraemer, Randal J. Keller, Journal of Chemical Health and Safety, Volume 16, Issue 2, March-April 2009, Pages 18-22, doi:10.1016/j.jchas.2008.06.003.

Effects of carbon dioxide inhalation on psychomotor and mental performance during exercise and recovery – Vercruyssen et al. (2007) “On separate days, 6 highly trained participants performed psychomotor tests while breathing for 60 min 3 carbon dioxide (CO(2)) mixtures (room air, 3% CO(2), or 4% CO(2)) prior to, between, and following two 15-min treadmill exercise bouts (70% VO(2)(max)). Each individual was extensively practiced (at least 4 days) before testing began, and both gas conditions and order of tasks were counterbalanced. Results showed physiological reactions and work-related psychomotor effects, but no effects of gas concentration on addition, multiplication, grammatical reasoning, or dynamic postural balance. These findings help define behavioral toxicity levels and support a re-evaluation of existing standards for the maximum allowable concentrations (also emergency and continuous exposure guidance levels) of CO(2). This research explored the selection of psychometric instruments of sufficient sensitivity and reliability to detect subtle changes in performance caused by exposure to low levels of environmental stress, in this case differential levels of CO(2) in the inspired air.” Vercruyssen M, Kamon E, Hancock PA., Int J Occup Saf Ergon. 2007;13(1):15-27. [Full text]

Health effects of increase in concentration of carbon dioxide in the atmosphere – Robertson (2006) “The toxic effects, to humans and other mammals, of concentrations of carbon dioxide in the atmosphere which are below the safe working level but above the present level are described. The likely physiological effects of the predicted increase in concentration of carbon dioxide in the atmosphere over the next 50 years are detailed.” A quote from the article: “At a carbon dioxide concentration of 600 ppm in an indoor atmosphere, the occupants become aware of deterioration in the atmosphere. At and above this level, some occupants began to display one or more of the classic symptoms of carbon dioxide poisoning, e.g. difficulty in breathing, rapid pulse rate, headache, hearing loss, hyperventilation, sweating and fatigue. At 1000 ppm, nearly all the occupants were affected. […] In the event that the atmospheric concentration of carbon dioxide reaches 600 ppm, the planet will have a permanent outdoor atmosphere exactly like that of a stuffy room. The conditions indoors in buildings of the type now available will become even more unpleasant and could easily reach 1000 ppm permanently with the results outlined above.” D. S. Robertson, Current science, 2006, vol. 90, no12, pp. 1607-1609. [Full text]

Carbon Dioxide Poisoning – Langford (2005) “Carbon dioxide is a physiologically important gas, produced by the body as a result of cellular metabolism. It is widely used in the food industry in the carbonation of beverages, in fire extinguishers as an `inerting’ agent and in the chemical industry. Its main mode of action is as an asphyxiant, although it also exerts toxic effects at cellular level. At low concentrations, gaseous carbon dioxide appears to have little toxicological effect. At higher concentrations it leads to an increased respiratory rate, tachycardia, cardiac arrhythmias and impaired consciousness. Concentrations >10% may cause convulsions, coma and death. Solid carbon dioxide may cause burns following direct contact. If it is warmed rapidly, large amounts of carbon dioxide are generated, which can be dangerous, particularly within confined areas. The management of carbon dioxide poisoning requires the immediate removal of the casualty from the toxic environment, the administration of oxygen and appropriate supportive care. In severe cases, assisted ventilation may be required. Dry ice burns are treated similarly to other cryogenic burns, requiring thawing of the tissue and suitable analgesia. Healing may be delayed and surgical intervention may be required in severe cases.” Langford, Nigel J., Toxicological Reviews, Volume 24, Number 4, 2005 , pp. 229-235(7).

Association of Ventilation Rates and CO2 Concentrations with Health andOther Responses in Commercial and Institutional Buildings – Seppänen et al. (1999) “This paper reviews current literature on the associations of ventilation rates and carbon dioxide concentrations in non-residential and non-industrial buildings (primarily offices) with health and other human outcomes. Twenty studies, with close to 30,000 subjects, investigated the association of ventilation rates with human responses, and 21 studies, with over 30,000 subjects, investigated the association of carbon dioxide concentration with these responses. Almost all studies found that ventilation rates below 10 Ls-1 per person in all building types were associated with statistically significant worsening in one or more health or perceived air quality outcomes. Some studies determined that increases in ventilation rates above 10 Ls-1 per person, up to approximately 20 Ls-1 per person, were associated with further significant decreases in the prevalence of sick building syndrome (SBS) symptoms or with further significant improvements in perceived air quality. The carbon dioxide studies support these findings. About half of the carbon dioxide studies suggest that the risk of sick building syndrome symptoms continued to decrease significantly with decreasing carbon dioxide concentrations below 800 ppm. The ventilation studies reported relative risks of 1.5–2 for respiratory illnesses and 1.1–6 for sick building syndrome symptoms for low compared to high low ventilation rates.” O. A. Seppänen, W. J. Fisk, M. J. Mendell, Indoor Air, Volume 9, Issue 4, pages 226–252, December 1999, DOI: 10.1111/j.1600-0668.1999.00003.x. [Full text]

Indoor Air Quality Investigations at Five Classrooms – Lee & Chang (1999) “Five classrooms, air-conditioned or naturally ventilated, at five different schools were chosen for comparison of indoor and outdoor air quality. Temperature, relative humidity (RH), carbon dioxide (CO2), sulphur dioxide (SO2), nitric oxide (NO), nitrogen dioxide (NO2), particulate matter with diameter less than 10 mm (PM10), formaldehyde (HCHO), and total bacteria counts were monitored at indoor and outdoor locations simultaneously. Respirable particulate matter was found to be the worst among parameters measured in this study. The indoor and outdoor average PM10 concentrations exceeded the Hong Kong standards, and the maximum indoor PM10 level was even at 472 μ;g/m3. Air cleaners could be used in classrooms to reduce the high PM10 concentration. Indoor CO2 concentrations often exceeded 1,000 μl/l indicating inadequate ventilation. Lowering the occupancy and increasing breaks between classes could alleviate the high CO2 concentrations. Though the maximum indoor CO2 level reached 5,900 μl/l during class at one of the sites, CO2 concentrations were still at levels that pose no health threats.” S. C. Lee, Maureen Chang, Indoor Air, Volume 9, Issue 2, pages 134–138, June 1999, DOI: 10.1111/j.1600-0668.1999.t01-2-00008.x.

Effects of sustained low-level elevations of carbon dioxide on cerebral blood flow and autoregulation of the intracerebral arteries in humans – Sliwka et al. (1998) “Cerebral blood flow velocity (CBFv) was measured by insonating the middle cerebral arteries of four subjects using a 2 Mhz transcranial Doppler. Ambient CO2 was elevated to 0.7% for 23 d in the first study and to 1.2% for 23 d in the same subjects in the second study. By non-parametric testing CBFv was elevated significantly by +35% above pre-exposure levels during the first 1-3 d at both exposure levels, after which CBFv progressively readjusted to pre-exposure levels. Despite similar CBFv responses, headache was only reported during the initial phase of exposure to 1.2% CO2. Vascular reactivity to CO2 assessed by rebreathing showed a similar pattern with the CBFv increases early in the exposures being greater than those elicited later. An increase in metabolic rate of the visual cortex was evoked by having the subjects open and close their eyes during a visual stimulus. Evoked CBFv responses measured in the posterior cerebral artery were also elevated in the first 1-3 d of both studies returning to pre-exposure levels as hypercapnia continued. Cerebral vascular autoregulation assessed by raising head pressure during 10 degrees head-down tilt both during the low-level exposures and during rebreathing was unaltered. There were no changes in the retinal microcirculation during serial fundoscopy studies. The time-dependent changes in CO2 vascular reactivity might be due either to retention of bicarbonate in brain extracellular fluid or to progressive increases in ventilation, or both. Cerebral vascular autoregulation appears preserved during chronic exposure to these low levels of ambient CO2.” Sliwka U, Krasney JA, Simon SG, Schmidt P, Noth J., Aviat Space Environ Med. 1998 Mar;69(3):299-306.

Sick Building Syndrome Symptoms among the Staff in Schools and Kindergartens: are the Levels of Volatile Organic Compounds and Carbon Dioxide Responsible? – Willers et al. (1996) “From a large questionnaire-based survey investigating the indoor air quality (IAQ) in 48 schools and 74 kindergartens, 21 schools were selected for mea surements of volatile organic compounds (VOC) and carbon dioxide (CO2) based on the prevalence of sick building syndrome (SBS) symptoms reported by the staff. The 10 schools with the lowest prevalence of SBS symptoms ‘healthy’) were compared to 11 schools with the highest prevalence (‘sick’; median value showing twice as many SBS symptoms reported). The concen trations of total VOCs (TVOC) in schools and kindergartens were low and within suggested guidelines. The levels of CO2 were higher than suggested guidelines in several cases. However, neither TVOC nor CO2 concentrations were associated with SBS symptoms. Thus, TVOC and CO2 concentrations do not seem to be useful as SBS risk indicators.” Stefan Willers, Sven Andersson, Rolf Andersson, Jörgen Grantén, Christina Sverdrup, Lars Rosell, Indoor and Built Environment July 1996 vol. 5 no. 4 232-235, doi: 10.1177/1420326X9600500406.

Effects of carbon dioxide inhalation on psychomotor and mental performance during exercise and recovery – Sheehy et al. (1982) “Psychomotor and mental tests involving reaction time, rotor pursuit, short-term memory for digits and letters, and reasoning ability were administered to subjects inhaling up to 5% CO2 in air and in gas mixtures containing 50% O2. The psychomotor and mental tests were given during the 6 min of recovery following 10 min of treadmill running at 80% of aerobic capacity. Although the subjects inhaled the CO2 during the entire exercise and recovery period there was no difference in performance between the CO2 inhalation condition and the control condition for any of the performance measures.” Sheehy, J B; Kamon, E; Kiser, D., Human Factors. Vol. 24, pp. 581-588. Oct. 1982.

Effects on man of high concentrations of carbon dioxide in relation to various oxygen pressures during exposures as long as 72 hours – Consolazio et al. (1947) No abstract. W. V. Consolazio, M. B. Fisher, N. Pace, I. J. Pecora, G. C. Pitts, A. R. Behnke, American Journal of Physiology, November 1947 vol. 151 no. 2 479-503.

Increasing atmospheric CO2 and allergies

Changes in Atmospheric CO2 Influence the Allergenicity of Aspergillus fumigatus – Lang-Yona et al. (2013) “Increased susceptibility to allergies has been documented in the Western world in recent decades. However, a comprehensive understanding of its causes is not yet available. It is therefore essential to understand trends and mechanisms of allergy-inducing agents, such as fungal conidia. In this study we investigated the hypothesis that environmental conditions linked to global atmospheric changes can affect the allergenicity of Aspergillus fumigatus, a common allergenic fungal species in indoor and outdoor environments and in airborne particulate matter. We show that fungi grown under present day CO2 levels (392 ppm) exhibit 8.5 and 3.5 fold higher allergenicity compared to fungi grown at preindustrial (280 ppm) and double (560 ppm) CO2 levels, respectively. A corresponding trend is observed in the expression of genes encoding for known allergenic proteins and in the major allergen Asp f1 concentrations, possibly due to physiological changes such as respiration rates and the nitrogen content of the fungus, influenced by the CO2 concentrations. Increased carbon and nitrogen levels in the growth medium also lead to a significant increase in the allergenicity. We propose that climatic changes such as increasing atmospheric CO2 levels and changes in the fungal growth medium may impact the ability of allergenic fungi such as Aspergillus fumigatus to induce allergies.” Naama Lang-Yona, Yishai Levin, Karen C. Dannemiller, Oded Yarden, Jordan Peccia, Yinon Rudich, Global Change Biology, DOI: 10.1111/gcb.12219.

Anthropogenic climate change and allergen exposure: The role of plant biology – Ziska & Beggs (2012) “Accumulation of anthropogenic gases, particularly CO2, is likely to have 2 fundamental effects on plant biology. The first is an indirect effect through Earth’s increasing average surface temperatures, with subsequent effects on other aspects of climate, such as rainfall and extreme weather events. The second is a direct effect caused by CO2-induced stimulation of photosynthesis and plant growth. Both effects are likely to alter a number of fundamental aspects of plant biology and human health, including aerobiology and allergic diseases, respectively. This review highlights the current and projected effect of increasing CO2 and climate change in the context of plants and allergen exposure, emphasizing direct effects on plant physiologic parameters (eg, pollen production) and indirect effects (eg, fungal sporulation) related to diverse biotic and abiotic interactions. Overall, the review assumes that future global mitigation efforts will be limited and suggests a number of key research areas that will assist in adapting to the ongoing challenges to public health associated with increased allergen exposure.” Lewis H. Ziska, Paul J. Beggs, Journal of Allergy and Clinical Immunology, Volume 129, Issue 1, January 2012, Pages 27–32,

Elevated atmospheric carbon dioxide concentrations amplify Alternaria alternata sporulation and total antigen production – Wolf et al. (2010) “BACKGROUND: Although the effect of elevated carbon dioxide (CO2) concentration on pollen production has been established in some plant species, impacts on fungal sporulation and antigen production have not been elucidated. OBJECTIVE: Our purpose was to examine the effects of rising atmospheric CO2 concentrations on the quantity and quality of fungal spores produced on timothy (Phleum pratense) leaves. METHODS: Timothy plants were grown at four CO2 concentrations (300, 400, 500, and 600 micromol/mol). Leaves were used as growth substrate for Alternaria alternata and Cladosporium phlei. The spore abundance produced by both fungi, as well as the size (microscopy) and antigenic protein content (ELISA) of A. alternata, were quantified. RESULTS: Leaf carbon-to-nitrogen ratio was greater at 500 and 600 micromol/mol, and leaf biomass was greater at 600 micromol/mol than at the lower CO2 concentrations. Leaf carbon-to-nitrogen ratio was positively correlated with A. alternata spore production per gram of leaf but negatively correlated with antigenic protein content per spore. At 500 and 600 micromol/mol CO2 concentrations, A. alternata produced nearly three times the number of spores and more than twice the total antigenic protein per plant than at lower concentrations. C. phlei spore production was positively correlated with leaf carbon-to-nitrogen ratio, but overall spore production was much lower than in A. alternata, and total per-plant production did not vary among CO2 concentrations. CONCLUSIONS: Elevated CO2 concentrations often increase plant leaf biomass and carbon-to-nitrogen ratio. Here we demonstrate for the first time that these leaf changes are associated with increased spore production by A. alternata, a ubiquitous allergenic fungus. This response may contribute to the increasing prevalence of allergies and asthma.” Wolf J, O’Neill NR, Rogers CA, Muilenberg ML, Ziska LH., Environ Health Perspect. 2010 Sep;118(9):1223-8. doi: 10.1289/ehp.0901867. [Full text]

Impacts of climate change on plant food allergens: a previously unrecognized threat to human health – Beggs & Walczyk (2008) “Global climate change has had, and will continue to have, many significant impacts on biological and human systems. There are now many studies of climate change impacts on aeroallergens, particularly pollen, including a study demonstrating significant increases in the major allergen content of ragweed pollen as a function of rising atmospheric carbon dioxide concentration ([CO2]). Recent research has also demonstrated more allergenic poison ivy in response to elevated [CO2]. Here, we suggest, for the first time, the potential for global climate change, and, in particular, increased [CO2] and temperature, to have an impact on the allergenicity of plant food allergens such as peanut. Such impacts could have significant impacts on associated allergic diseases, and pose a previously unrecognized threat to human health. There is an urgent need for research on the impacts of climate change on plant food allergens.” Paul John Beggs, Nicole Ewa Walczyk, Air Quality, Atmosphere & Health, October 2008, Volume 1, Issue 2, pp 119-123, DOI: 10.1007/s11869-008-0013-z. [Full text]

Pollen production by Pinus taeda growing in elevated atmospheric CO2 – Ladeau & Clark (2006) “Rising concentrations of atmospheric CO2 may have important consequences for reproductive allocation in forest trees. Changes in pollen production could influence population dynamics and is likely to have important consequences for human health. This is the first study to evaluate pollen production by forest trees in response to rising atmospheric CO2. Our research objective was to quantify pollen production by Loblolly Pine (Pinus taeda L.) trees growing in elevated CO2 (ambient + 200 µl l−1) since 1996. Trees grown in high-CO2 plots first began producing pollen while younger and at smaller sizes relative to ambient-grown trees. Pollen cone and airborne pollen grain abundances were significantly greater in the fumigated stands. We conclude that the greater number of mature trees in high-CO2 plots resulted in greater pollen production at the stand level. Precocious pollen production has important implications for fertilization and pollen dispersal from young, dense stands. Increasing levels of airborne pollen raise concerns for escalating rates of human respiratory disease.” S. L. Ladeau, J. S. Clark, Functional Ecology, Volume 20, Issue 3, pages 541–547, June 2006, DOI: 10.1111/j.1365-2435.2006.01133.x. [Full text]

Biomass and toxicity responses of poison ivy (Toxicodendron radicans) to elevated atmospheric CO2 – Mohan et al. (2006) “Contact with poison ivy (Toxicodendron radicans) is one of the most widely reported ailments at poison centers in the United States, and this plant has been introduced throughout the world, where it occurs with other allergenic members of the cashew family (Anacardiaceae). Approximately 80% of humans develop dermatitis upon exposure to the carbon-based active compound, urushiol. It is not known how poison ivy might respond to increasing concentrations of atmospheric carbon dioxide (CO2), but previous work done in controlled growth chambers shows that other vines exhibit large growth enhancement from elevated CO2. Rising CO2 is potentially responsible for the increased vine abundance that is inhibiting forest regeneration and increasing tree mortality around the world. In this 6-year study at the Duke University Free-Air CO2 Enrichment experiment, we show that elevated atmospheric CO2 in an intact forest ecosystem increases photosynthesis, water use efficiency, growth, and population biomass of poison ivy. The CO2 growth stimulation exceeds that of most other woody species. Furthermore, high-CO2 plants produce a more allergenic form of urushiol. Our results indicate that Toxicodendron taxa will become more abundant and more “toxic” in the future, potentially affecting global forest dynamics and human health.” Jacqueline E. Mohan, Lewis H. Ziska, William H. Schlesinger, Richard B. Thomas, Richard C. Sicher, Kate George, and James S. Clark, PNAS June 13, 2006 vol. 103 no. 24 9086-9089, doi: 10.1073/pnas.0602392103. [Full text]

Increasing Amb a 1 content in common ragweed (Ambrosia artemisiifolia) pollen as a function of rising atmospheric CO2 concentration – Singer et al. (2005) “Although the impact of increasing atmospheric carbon dioxide concentration ([CO2]) on production of common ragweed (Ambrosia artemisiifolia L.) pollen has been examined in both indoor and outdoor experiments, the relationship between allergen expression and [CO2] is not known. An enzyme-linked immunosorbent assay (ELISA) was used to quantify Amb a 1, ragweed’s major allergen, in protein extracted from pollen of A. artemisiifolia grown at different [CO2] values in a previous experiment. The concentrations used approximated atmospheric pre-industrial conditions (i.e. at the end of the 19th century), current conditions, and the CO2 concentration projected for the middle of the 21st century (280, 370 and 600 μmol mol–1 CO2, respectively). Although total pollen protein remained unchanged, significant increases in Amb a 1 allergen were observed between pre-industrial and projected future [CO2] and between current and projected future [CO2] (1.8 and 1.6 times, respectively). These data suggest that recent and projected increases in [CO2] could directly increase the allergenicity of ragweed pollen and consequently the prevalence and / or severity of seasonal allergic disease. However, genetic and abiotic factors governing allergen expression will need to be better established to fully understand these data and their implications for public health.” Ben D. Singer A C, Lewis H. Ziska B D, David A. Frenz C, Dennis E. Gebhard C, James G. Straka, Functional Plant Biology 32(7) 667–670, [Full text]

Production of allergenic pollen by ragweed (Ambrosia artemisiifolia L.) is increased in CO2-enriched atmospheres – Wayne et al. (2002) “Background: The potential effects of global climate change on allergenic pollen production are still poorly understood. Objective: To study the direct impact of rising atmospheric CO2 concentrations on ragweed (Ambrosia artemisiifolia L.) pollen production and growth. Methods: In environmentally controlled greenhouses, stands of ragweed plants were grown from seed through flowering stages at both ambient and twice-ambient CO2 levels (350 vs 700 μL L−1). Outcome measures included stand-level total pollen production and end-of-season measures of plant mass, height, and seed production. Results: A doubling of the atmospheric CO2 concentration stimulated ragweed-pollen production by 61% (P = 0.005). Conclusions: These results suggest that there may be significant increases in exposure to allergenic pollen under the present scenarios of global warming. Further studies may enable public health groups to more accurately evaluate the future risks of hay fever and respiratory diseases (eg, asthma) exacerbated by allergenic pollen, and to develop strategies to mitigate them.” Peter Wayne, Susannah Foster, John Connolly, Fakhri Bazzaz, Paul Epstein, Annals of Allergy, Asthma & Immunology, Volume 88, Issue 3, March 2002, Pages 279–282, [Full text]

Rising CO2 and pollen production of common ragweed (Ambrosia artemisiifolia L.), a known allergy-inducing species: implications for public health – Ziska & Caulfield (2000) “Although environmental factors such as precipitation and temperature are recognized as influencing pollen production, the impact of rising atmospheric carbon dioxide concentration ([CO2]) on the potential growth and pollen production of hay-fever-inducing plants is unknown. Here we present measurements of growth and pollen production of common ragweed (Ambrosia artemisiifolia L.) from pre-industrial [CO2] (280 mol mol–1) to current concentrations (370 mol mol–1) to a projected 21st century concentration (600 mol mol–1). We found that exposure to current and elevated [CO2] increased ragweed pollen production by 131 and 320%, respectively, compared to plants grown at pre-industrial [CO2]. The observed stimulations of pollen production from the pre-industrial [CO2] were due to an increase in the number (at 370 mol mol–1) and number and size (at 600 mol mol–1) of floral spikes. Overall, floral weight as a percentage of total plant weight decreased (from 21% to 13%), while investment in pollen increased (from 3.6 to 6%) between 280 and 600 mol mol–1 CO2. Our results suggest that the continuing increase in atmospheric [CO2] could directly influence public health by stimulating the growth and pollen production of allergy-inducing species such as ragweed.” Lewis H. Ziska and Frances A. Caulfield, Australian Journal of Plant Physiology 27(10) 893 – 898, doi:10.1071/PP00032. [Full text]

Increased levels of airborne fungal spores in response to Populus tremuloides grown under elevated atmospheric CO2 – Klironomos et al. (1997) “Soil fungi are important components of terrestrial ecosystems. They function as decomposers, pathogens, parasites, and mutualistic symbionts. Their main mode of dispersal is to liberate spores into the atmosphere. In this study we tested the hypothesis that a higher atmospheric CO2 concentration will induce greater sporulation in common soil fungi, leading to higher concentrations of fungal propagules in the atmosphere. In our field experiment, the concentration of airborne fungal propagules, mostly spores, increased fourfold under twice-ambient CO2 concentrations. Analysis of decomposing leaf litter (likely the main source of airborne fungal propagules) indicated that the fungi produced fivefold more spores under elevated CO2. Our results provide evidence that elevations in atmospheric CO2 concentration can directly affect microbial function, which may have important implications for litter decay, fungal dispersal, and human respiratory health. Key words: atmospheric CO2, fungal spores, global change, Populus tremuloides.” John N. Klironomos, Matthias C. Rillig, Michael F. Allen, Donald R. Zak, Kurt S. Pregitzer, Mark E. Kubiske, Canadian Journal of Botany, 1997, 75(10): 1670-1673, 10.1139/b97-880.

Extreme carbon dioxide events

This section lists papers on some extreme events where carbon dioxide has caused deaths or serious harm. It should be noted that this is not very relevant to the carbon dioxide levels associated with current global warming. However, for some carbon capture and storage scenarios these events serve as practical examples to what happens during high local carbon dioxide levels.

Non-volcanic CO2 Earth degassing: Case of Mefite d’Ansanto (southern Apennines), Italy – Chiodini et al. (2010) “Mefite d’Ansanto, southern Apennines, Italy is the largest natural emission of low temperature CO2 rich gases, from non-volcanic environment, ever measured in the Earth. The emission is fed by a buried reservoir, made up of permeable limestones and covered by clayey sediments. We estimated a total gas flux of ~2000 tons per day. Under low wind conditions, the gas flows along a narrow natural channel producing a persistent gas river which has killed over a period of time people and animals. The application of a physical numerical model allowed us to define the zones which potentially can be affected by dangerous CO2 concentration at breathing height for humans.” Chiodini, G., D. Granieri, R. Avino, S. Caliro, A. Costa, C. Minopoli, and G. Vilardo (2010), Geophys. Res. Lett., 37, L11303, doi:10.1029/2010GL042858.

Asphyxiation Due to Dry Ice in a Walk-in Freezer – Dunford et al. (2009) “Background: Exposure to a high concentration of environmental carbon dioxide (CO2) can result in poisoning through direct toxicity and by displacing atmospheric oxygen (O2). Dry ice undergoes sublimation to a gaseous state at −78.5°C (−109.3°F), which is heavier than air and can accumulate in dependent areas. Case Report: We report the case of a 59-year-old man found in cardiac arrest shortly after entering a recently repaired walk-in freezer that contained dry ice. First responders and bystanders did not recognize the proximate hazardous environment but were fortunately uninjured. A careful Emergency Department history coupled with rapid case investigation by the Medical Examiner’s Office led to the determination of the cause of death and the elimination of the ongoing hazard. Conclusion: This case illustrates the lethal consequences of improper storage of dry ice and the need to consider toxic environmental exposure as a cause of sudden cardiac arrest.” James V. Dunford, Jon Lucas, Nick Vent, Richard F. Clark, F. Lee Cantrell, The Journal of Emergency Medicine, Volume 36, Issue 4, May 2009, Pages 353-356, doi:10.1016/j.jemermed.2008.02.051.

A Carbon Dioxide Fatality from Dry Ice – Srisont et al. (2009) “This report documents a rare case of carbon dioxide intoxication in a young healthy male. The deceased hid in a small plastic container, size 1.5 × 1 × 1 m, and within 5 min he was located suffering convulsions and was reported as dead within minutes. Scene investigation revealed dry ice in the container. Autopsy findings were unremarkable. The probable cause of the convulsions was carbon dioxide intoxication due to both the dry ice sublimation and the small confined space in which he was hiding. This report emphasizes the significance of scene investigation in establishing the cause of the death.” Smith Srisont, Thamrong Chirachariyavej, A. V. M. Vichan Peonim, Journal of Forensic Sciences, Volume 54, Issue 4, pages 961–962, July 2009, DOI: 10.1111/j.1556-4029.2009.01057.x. [Full text]

A shallow-layer model for heavy gas dispersion from natural sources: Application and hazard assessment at Caldara di Manziana, Italy – Costa et al. (2008) “Several nonvolcanic sources in central Italy emit a large amount of carbon dioxide (CO2). Under stable atmospheric conditions and/or in the presence of topographic depressions, the concentration of CO2, which has a molecular mass greater than that of air, can reach high values that are lethal to humans or animals. Several episodes of this phenomenon were recorded in central Italy and elsewhere. In order to validate a model for the dispersion of a heavy gas and to assess the consequent hazard, we applied and tested the code TWODEE-2, an improved version of the established TWODEE model, which is based on a shallow-layer approach that uses depth-averaged variables to describe the flow behavior of dense gas over complex topography. We present results for a vented CO2 release at Caldara di Manziana in central Italy. We find that the model gives reliable results when the input quantity can be properly defined. Moreover, we show that the model can be a useful tool for gas hazard assessment by evaluating where and when lethal concentrations for humans and animals are reached.” Costa, A., G. Chiodini, D. Granieri, A. Folch, R. K. S. Hankin, S. Caliro, R. Avino, and C. Cardellini (2008), Geochem. Geophys. Geosyst., 9, Q03002, doi:10.1029/2007GC001762. [Full text]

Degassing Lakes Nyos and Monoun: Defusing certain disaster – Kling et al. (2005) “Since the catastrophic releases of CO2 in the 1980s, Lakes Nyos and Monoun in Cameroon experienced CO2 recharge at alarming rates of up to 80 mol/m2 per yr. Total gas pressures reached 8.3 and 15.6 bar in Monoun (2003) and Nyos (2001), respectively, resulting in gas saturation levels up to 97%. These natural hazards are distinguished by the potential for mitigation to prevent future disasters. Controlled degassing was initiated at Nyos (2001) and Monoun (2003) amid speculation it could inadvertently destabilize the lakes and trigger another gas burst. Our measurements indicate that water column structure has not been compromised by the degassing and local stability is increasing in the zones of degassing. Furthermore, gas content has been reduced in the lakes ≈12-14%. However, as gas is removed, the pressure at pipe inlets is reduced, and the removal rate will decrease over time. Based on 12 years of limnological measurements we developed a model of future removal rates and gas inventory, which predicts that in Monoun the current pipe will remove ≈30% of the gas remaining before the natural gas recharge balances the removal rate. In Nyos the single pipe will remove ≈25% of the gas remaining by 2015; this slow removal extends the present risk to local populations. More pipes and continued vigilance are required to reduce the risk of repeat disasters. Our model indicates that 75-99% of the gas remaining would be removed by 2010 with two pipes in Monoun and five pipes in Nyos, substantially reducing the risks.” George W. Kling, William C. Evans, Greg Tanyileke, Minoru Kusakabe, Takeshi Ohba, Yutaka Yoshida, and Joseph V. Hell, PNAS October 4, 2005 vol. 102 no. 40 14185-14190, doi: 10.1073/pnas.0502274102. [Full text]

Recent pH and CO2 profiles at Lakes Nyos and Monoun, Cameroon: implications for the degassing strategy and its numerical simulation – Kusakabe et al. (2000) “In situ pH profiles are reported for the first time for Lakes Nyos and Monoun. The pH profiles were converted to CO2 profiles using HCO3− profiles calculated from conductivity data. Recent observations (1993–1996) at Lake Nyos indicates that CO2 still accumulates below 180 m depth at a rate of 125 Mmol year−1. At Lake Monoun, the majority of CO2 is present below a depth of 60 m, only 25 m below the saturation depth. Consequently, a potential danger of gas explosion is high at both lakes, and artificial degassing of the lakes should be performed as soon as possible. A system for industrial degassing of the lakes is proposed. The system, based on the self-sustained gas lift principle, consists of multiple pipes (14 cm in diameter) with different intake depths; 12 pipes for Lake Nyos (four each at 185, 195 and 205 m) and three pipes for Lake Monoun (at 70, 80 and 90 m). The stepped degassing at different depths is intended to keep the maximum stability of the lakes. The proposed degassing operation was simulated using the dyresm code for both lakes. In 5 years, approximately 50% of currently dissolved CO2 in Lake Nyos and 90% in Lake Monoun will be removed. The expected changes in the thermal and chemical structures of the lakes as degassing proceeds will be most easily monitored with a carefully calibrated CTD equipped with a pH sensor. The simulation indicates that the discharged degassed water will sink to a level of neutral buoyancy, i.e. to a maximum of 70 m at Lake Nyos and 35 m at Lake Monoun. There would be no possibility of triggering a gas explosion by this plunge of discharged water because the water present there would have already been replaced by water at lower CO2 concentration, during the degassing from shallower pipes.” M Kusakabe, G.Z Tanyileke, S.A McCord, S.G Schladow, Journal of Volcanology and Geothermal Research, Volume 97, Issues 1-4, April 2000, Pages 241-260, doi:10.1016/S0377-0273(99)00170-5.

Possible asphyxiation from carbon dioxide of a cross-country skier in eastern California: a deadly volcanic hazard – Hill (2000) “This report describes an incident in which exceedingly high levels of carbon dioxide may have contributed to the death of a skier in eastern California. A cross-country skier was found dead inside a large, mostly covered snow cave, 1 day after he was reported missing. The autopsy report suggests that the skier died of acute pulmonary edema consistent with asphyxiation; carbon dioxide measurements inside the hole in which he was found reached 70%. This area is known for having a high carbon dioxide flux attributed to degassing of a large body of magma (molten rock) 10 to 20 km beneath the ski area. The literature describes many incidents of fatal carbon dioxide exposures associated with volcanic systems in other parts of the world. We believe this case represents the first reported death associated with volcanically produced carbon dioxide in the United States. Disaster and wilderness medicine specialists should be aware of and plan for this potential health hazard associated with active volcanoes.” Peter M. Hill, Wilderness & Environmental Medicine, Volume 11, Issue 3, September 2000, Pages 192-195, doi:10.1580/1080-6032(2000)011[0192:PAFCDO]2.3.CO;2.

Fatal intoxication due to an unexpected presence of carbon dioxide – Guillemin & Horisberger (1994) “A fatal accident which occurred in a tank containing a sludge made of wine and activated charcoal is described. Similar accidents in the wine industry seem to have never been reported before. Initially, the cause of death was not obvious and became clear only after the autopsy confirmed the presence of a very high concentration of carbon dioxide in blood. It is shown in this paper how the concentration of carbon dioxide in the tank could be estimated from its solubility in water, assuming a realistic content of this gas in the wine remaining in the sludge. Moreover the accident was analysed by the fault tree method which revealed that, as well as the deficiencies in risk management of such companies, the unsuspected presence of carbon dioxide played a significant role.” Michel P. Guillemin and B. Horisberger, Ann Occup Hyg (1994) 38 (6): 951-957. doi: 10.1093/annhyg/38.6.951.

CO2-rich gases from Lakes Nyos and Monoun, Cameroon; Laacher See, Germany; Dieng, Indonesia, and Mt. Gambier, Australia—variations on a common theme – Giggenbach et al. (1991) “Helium (RA = 3.0 to 5.6) and carbon (δ13C from −7.2 to −3.4‰) isotopic compositions, and relative CO2, CH4, N2, He and Ar contents of CO2-rich gases from Lakes Nyos and Monoun, Cameroon; Laacher See, Germany; Dieng Volcanic Plateau, Indonesia, and a well at Mt. Gambier, Australia, point to a common, essentially magmatic origin. … Otherwise, gas may accumulate to form a stable pocket (Mt. Gambier). Minor leakage from such pockets may lead to surface discharges of CO2-rich gases as at Laacher See, re-absorption into shallow groundwater to the formation of the low-salinity, CO2-charged waters encountered at Lakes Nyos and Monoun. The occurrence of these high-CO2, low-temperature systems is likely to be favored in tectonically active regions, allowing deep, possibly mantle gases to rise, but with sufficiently low regional heat flows to prevent the establishment of large-scale geothermal activity.” W.F. Giggenbach, Y. Sano, H.U. Schmincke, Journal of Volcanology and Geothermal Research, Volume 45, Issues 3-4, April 1991, Pages 311-323, doi:10.1016/0377-0273(91)90065-8.

Water and gas chemistry of Lake Nyos and its bearing on the eruptive process – W.F. Giggenbach (1990) “The isotopic and chemical composition of water samples collected from Lake Nyos some two and eight weeks after the eruption of August 21, 1986 point to the existence of three distinct mixing regimes involving three water components. An essentially homogeneous, unmixed body of water at depths > 100 m, overlain by water increasingly affected by surface evaporation and a 5–10-m layer containing recent, but pre-eruption rain water. The cationic constituents (Na, K, Mg, Ca, Mn, Fe) of the lake water correspond to the dissolution of around 0.1 g of local rock, the waters are close to saturation with respect to siderite. The composition of the gas dissolved in the deep lake waters (0.65% b.w. of CO2, PCO2 = 4.4b) corresponds (in mmol mol−1) to 996 CO2, 2.0 CH4, 2.0 N2, 0.05 Ar, 0.004 He, 0.0002 H2, 0.0001 Ne, < 0.01 O2, < 0.004 H2S, < 0.001 CO. The isotopic compositions of CO213C = -3.4‰) and of He (Rair = 5.5) suggest deep magmatic origins, the 13C and 2H content of CH4 organic sedimentary origin, the presence of aromatic hydrocarbons indicates very high temperatures of hydrocarbon formation. Exsolution of gas will first lead to the precipitation of siderite then iron hydroxide. The chemistry of the lake waters points to a loss of some 240,000 t of CO2 from the upper 100 m of the lake, their isotopic composition is consistent with the assumption that the eruption was triggered by the accumulation of cold rain waters at the lake surface prior to the eruption inducing partial convective overturn. There is no need to invoke addition of chemical or isotopic constituents from deeper levels during the eruption.” W.F. Giggenbach, Journal of Volcanology and Geothermal Research, Volume 42, Issue 4, 15 August 1990, Pages 337-362, doi:10.1016/0377-0273(90)90031-A.

The Lake Nyos gas disaster: chemical and isotopic evidence in waters and dissolved gases from three Cameroonian crater lakes, Nyos, Monoun and Wum – Kusakabe et al. (1989) “To better understand the cause of the Nyos gas disaster of August 21, 1986, we conducted geochemical and limnological surveys in October 1986, of three lakes (Nyos, Monoun and Wum) which are located in the Cameroon volcanic zone that is characterized by a prevalence of young alkaline basalts and basanitoids. … The August 1986 gas bursts from Lake Nyos were most likely caused by rapid exsolution of dissolved CO2 within the lake; an explosive process such as a phreatic eruption or a CO2 gas-jetting from beneath the bottom is unlikely because of low concentrations of Cl and SO42−, no oxygen isotopic shift, low turbidity, and no reported perturbation of the bottom sediments. Exsolution of CO2 bubbles could occur if CO2-saturated bottom water was displaced upwards by an increased influx of high salinity water from the bottom during the rainy season. Exsolution of CO2 at the upper layers was possibly accelerated by upwelling of a two-phase fluid (CO2 bubbles and solution), a mechanism known as a pneumatic lift pump, resulting in discharge of a large amount of CO2 gas. The H2S concentration in the gas cloud must have been kept far below the lethal level because of a high Fe2+ concentration of the lake water.” Minoru Kusakabe, Takashi Ohsumi, Shigeo Aramaki, Journal of Volcanology and Geothermal Research, Volume 39, Issues 2-3, November 1989, Pages 167-185, doi:10.1016/0377-0273(89)90056-5.

The gas cloud of Lake Nyos (Cameroon, 1986): Results of the Italian technical mission – Barberi et al. (1989) “On August 21, 1986, a gas cloud issued from Lake Nyos in Cameroon killed over 1700 people. An Italian technical mission reached the area seven days later and obtained the first field evidences of the catastrophe. On the basis of observations and measurements in the field and of samples collected, the origin of the gas outburst is attributed to a phreatic explosion from beneath the bed of the lake. This interpretation appears to fit well the observed and reported phenomena, and seems perfectly consistent with the geological-geothermal conditions of the area.” F. Barberi, W. Chelini, G. Marinelli, M. Martini, Journal of Volcanology and Geothermal Research, Volume 39, Issues 2-3, November 1989, Pages 125-134, doi:10.1016/0377-0273(89)90053-X.

Lake Nyos disaster, Cameroon, 1986: the medical effects of large scale emission of carbon dioxide? – Baxter et al. (1989) “Carbon dioxide was blamed for the deaths of around 1700 people in Cameroon, west Africa, in 1986 when a massive release of gas occurred from Lake Nyos, a volcanic crater lake. The clinical findings in 845 survivors seen at or admitted to hospital were compatible with exposure to an asphyxiant gas. Rescuers noted cutaneous erythema and bullae on an unknown proportion of corpses and 161 (19%) survivors treated in hospital; though these lesions were initially believed to be burns from acidic gases, further investigation suggested that they were associated with coma states caused by exposure to carbon dioxide in air. The disaster at Lake Nyos and a similar event at Lake Monoun, Cameroon, two years previously provide new information on the possible medical effects of large scale emissions of carbon dioxide, though the presence of other toxic factors in these gas releases cannot be excluded.” P. J. Baxter, M. Kapila, D. Mfonfu, BMJ 298 : 1437 doi: 10.1136/bmj.298.6685.1437 (Published 27 May 1989). [Full text]

Mechanisms of the Nyos carbon dioxide disaster and of so-called phreatic steam eruptions – Tazieff (1989) “During the night of August 21, 1986, a huge volume of concentrated CO2 was emitted by the crater (maar) of Nyos, Cameroon. It killed more than 1700 people and all animal life as far as 14 km away. Two hypotheses have been put forward to account for this disaster. The chronologically first one imputes it to have been a phreatic eruption, exceptionally CO2-rich, as had been the case in February 1979 on the Diëng Plateau in Central Java, Indonesia, where the erupting crater was lake-less. The second one claims a limnic origin for the CO2 release, through an overturn of the 220 m-deep Lake Nyos, the hypolimnium of which was supposed to be oversaturated by dissolved gas of volcanic origin. The present paper points to six observed facts for which the eruptive hypothesis easily accounts, and which the authors of the limnic one do ignore.” Haroun Tazieff, Journal of Volcanology and Geothermal Research, Volume 39, Issues 2-3, November 1989, Pages 109-116, doi:10.1016/0377-0273(89)90051-6.

Origin of carbon dioxide emanation from the 1979 Dieng eruption, Indonesia: Implications for the origin of the 1986 Nyos catastrophe – Allard et al. (1989) “In February 1979, CO2 emanations accompanying a phreatic eruption killed 142 people at Dieng volcano, Central Java. The gas emitted was nearly pure carbon dioxide, with subordinate amounts of methane and sulfur compounds. … It is proposed that magmatic carbon dioxide, accumulated beneath the Dieng volcanic complex, was the source of the lethal gas, the effusion of which was triggered by the pressure release generated by the phreatic eruption. The total CO2 discharge of the 1979 Dieng event might have approached 0.1 km3, i.e. close to the lower output estimated for the 1986 Nyos catastrophe. The Dieng example demonstrates that expansion and then effusion of pure magmatic carbon dioxide, accumulated at shallow levels beneath volcanoes, may account for a major hazard from phreatic eruptions, be it a trigger or only a consequence of the eruptions.” P. Allard, D. Dajlevic, C. Delarue, Journal of Volcanology and Geothermal Research, Volume 39, Issues 2-3, November 1989, Pages 195-206, doi:10.1016/0377-0273(89)90058-9.

Medical evaluation of the victims of the 1986 Lake Nyos disaster – Wagner et al. (1988) “A cloud of carbon dioxide gas, with an estimated volume of 1 km3 was released from Lake Nyos, a volcanic crater lake in Cameroon, Africa, causing 1700 to 2000 human fatalities as well as killing thousands of livestock and wild animals. At the request of the Cameroonian Government, the Office of Foreign Disaster Assistance of the U.S. Department of State sent a multidisciplinary team which included 2 forensic pathologists to assist the Government of Cameroon in investigating this natural disaster. The medical evaluation was concentrated in 3 areas: the autopsy of human and animal fatalities, examination and interview of survivors, and examination of the scene of the disaster. Toxicologic specimens were obtained at autopsy, and numerous samples of lake water were collected. The autopsy findings were consistent with asphyxia. The results of chemical analyses excluded many volatiles but not carbon dioxide as the toxic agent. The exact source of this gas continues to be a subject of a heated geologic debate, but fermentation of organic materials in the lake water has been eliminated on the basis of C14 isotope studies. This investigation underlines the value of forensic pathologists in epidemiological studies and in the examination of living persons.” Wagner GN, Clark MA, Koenigsberg EJ, Decata SJ., J Forensic Sci. 1988 Jul;33(4):899-909.

The 1986 Lake Nyos Gas Disaster in Cameroon, West Africa – Kling et al. (1987) “The sudden, catastrophic release of gas from Lake Nyos on 21 August 1986 caused the deaths of at least 1700 people in the northwest area of Cameroon, West Africa. Chemical, isotopic, geologic, and medical evidence support the hypotheses that (i) the bulk of gas released was carbon dioxide that had been stored in the lake’s hypolimnion, (ii) the victims exposed to the gas cloud died of carbon dioxide asphyxiation, (iii) the carbon dioxide was derived from magmatic sources, and (iv) there was no significant, direct volcanic activity involved. The limnological nature of the gas release suggests that hazardous lakes may be identified and monitored and that the danger of future incidents can be reduced.” George W. Kling, Michael A. Clark, Glen N. Wagner, Harry R. Compton, Alan M. Humphrey, Joseph D. Devine, William C. Evans, John P. Lockwood, Michele L. Tuttle and Edward J. Koenigsberg, Science 10 April 1987: Vol. 236 no. 4798 pp. 169-175, DOI: 10.1126/science.236.4798.169.

Origin of the lethal gas burst from Lake Monoun, Cameroun – Sigurdsson et al. (1987) “On 15 August, 1984, a lethal gas burst issued from a submerged 96-m-deep crater in Lake Monoun in Cameroun, western Africa, killing 37 people. The event was associated with a landslide from the eastern crater rim, which slumped into deep water. … Gases effervescing from depressurized deep waters are dominantly CO2 with minor CH4, having δ13C of −7.18 and −54.8 per mil, respectively. … The resultant ebullition of CO2 from deep lake waters led to a gas burst at the surface and locally generated a water wave up to 5 m high. People travelling through the gas cloud were asphyxiated, presumably from CO2, and suffered skin discoloration from unidentified components.” H. Sigurdsson, J.D. Devine, F.M. Tchua, F.M. Presser, M.K.W. Pringle, W.C. Evans, Journal of Volcanology and Geothermal Research, Volume 31, Issues 1-2, March 1987, Pages 1-16, doi:10.1016/0377-0273(87)90002-3.

An example of health hazard: People killed by gas during a phreatic eruption: Diëng plateau (Java, Indonesia), February 20th 1979 – Le Guern et al. (1982) “On February 20th, 1979, 142 inhabitants of Dieng Plateau (Indonesia) were asphyxiated by poisonous gases during a mild phreatic eruption. From later fields gas collection and analysis, the casualties are considered to be due to CO2 rich volcanic gases.” F. Le Guern, H. Tazieff and R. Faivre Pierret, Bulletin of Volcanology, Volume 45, Number 2, 153-156, DOI: 10.1007/BF02600430.

Posted in Adaptation & Mitigation, Global warming effects | 4 Comments »

Papers on ticks and global warming

Posted by Ari Jokimäki on August 11, 2011

This is a list of papers on global warming effects on tick populations and the diseases they spread. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (September 12, 2011): Beugnet & Marié (2009), Dautel et al. (2006), Bullová et al. (2009), Dantas-Torres (2010), and Gern et al. (2008) added.

Modelling the effects of recent changes in climate, host density and acaricide treatments on population dynamics of Ixodes ricinus in the UK – Dobson & Randolph (2011) “A population model for the tick Ixodes ricinus, the most significant vector of pathogens in Europe, is used to explore the relative impact of changes in climate, host density and acaricide-treated hosts on tick abundance and seasonality. A rise in temperature of the sort witnessed since 1989 speeds up the inter-stadial development of ticks, thereby reducing the cumulative effect of constant daily mortality rates and potentially raising population levels. The predicted earlier onset of tick-questing activity in the spring, due to stage-specific temperature thresholds, could increase contact between ticks and humans during recreational visits to the countryside in spring holidays. These tick population effects vary geographically with background climate. The significant increase in deer abundance across Europe, including the UK, in recent decades is predicted to drive tick population increases, the effect varying with the initial density of hosts. In areas only recently colonized by deer, tick numbers are predicted to rise dramatically (given suitable climatic conditions). Where host densities are already high, however, further increases may reduce numbers of questing ticks; unfed ticks leave the questing population more rapidly, even though the overall tick population (and therefore pathogen transmission potential) increases. Culling high-density deer populations as a control measure could, therefore, initially cause an apparent increase in questing ticks, with the predicted long-term population trajectory depending on the severity of the cull. Conversely, the further addition of large hosts (e.g. sheep) would effectively reduce the number of questing ticks and therefore the risk to humans. If such sheep were treated with acaricide, tick populations are predicted to decrease rapidly, to an extent that depends on the relative abundance of wild (untreated) and treated hosts. Tick control in designated areas may be achieved by using sheep in this way as ‘lethal mops’, as used to occur in the past when sheep were regularly dipped. Synthesis and applications: Both abiotic and biotic environmental changes witnessed recently could have contributed to apparent increases in tick populations, especially where these environmental factors were limiting in the past. The release of additional hosts treated with long-lasting acaricide is potentially an effective control strategy.” Andrew D. M. Dobson, Sarah E. Randolph, Journal of Applied Ecology, Volume 48, Issue 4, pages 1029–1037, August 2011, DOI: 10.1111/j.1365-2664.2011.02004.x.

Mathematical modelling of the impact of climatic conditions in France on Rhipicephalus sanguineus tick activity and density since 1960 – Beugnet et al. (2011) “Rhipicephalus sanguineus, the brown dog tick, has a worldwide distribution in areas with a relatively warm climate, including mild winters. This tick plays an important role as vector for various animal and human pathogens, including bacteria and protozoa. Based on precise daily meteorological data from the past 40 years, combined with mathematical modelling designed to predict tick activity, two modelling approaches were developed. The first examined the evolution of the number of weeks with favourable biological conditions for ticks in four French cities located at various latitudes of the country: Nîmes in the south, Paris in the north, Lyon in the east and Nantes in the west. The second analysed the extension of the geographical surface area in km(2) where the biological conditions favour tick activity for at least 12 weeks per year. Both analyses revealed clear evidence of increased temperatures coupled with an augmented tick activity index in three of the four cities. However, the change was not significant in Nîmes, where the climate is Mediterranean and the tick is already endemic. For Paris, Lyon and Nantes, the activity index values have increased significantly, i.e. by 4.4%, 4.0% and 3.4%, respectively. The distribution of the activity index values is evolving strongly with significantly fewer values below 50% since the 1960s and a clear decrease of values between 20% and 50% during the latest decade. Between 1960 and 2000, the theoretical extension of the surface area where the climatic index is suitable for R. sanguineus has increased by 66%. Even though several other important factors, such as changes in biotopes or human activity, are not included in this study, the resulting patterns and trends are noticeable. Our models constitute the first demonstration of the impact of climate change on the activity and distribution of ticks and confirm the observed northward migration trend for this Mediterranean domestic tick.” Beugnet F, Kolasinski M, Michelangeli PA, Vienne J, Loukos H., Geospat Health. 2011 May;5(2):255-63. [Full text]

A clear and present danger: tick-borne diseases in Europe – Heyman et al. (2010) “Ticks can transmit a variety of viruses, bacteria or parasites that can cause serious infections or conditions in humans and animals. While tick-borne diseases are becoming an increasing and serious problem in Europe, tick-borne diseases are also responsible for major depressions in livestock production and mortality in sub-Saharan Africa, Latin America and Asia. This review will focus on the most important circulating tick-transmitted pathogens in Europe (Borrelia spp., Anaplasma phagocytophilum, Babesia spp., tick-borne encephalitis virus, Rickettsia spp. and Crimean-Congo hemorrhagic fever virus).” Heyman, Paul, Cochez, Christel, Hofhuis, Agnetha, van der Giessen, Joke, Sprong, Hein, Porter, Sarah Rebecca, Losson, Bertrand, Saegerman, Claude, Donoso-Mantke, Oliver, Niedrig, Matthias, Papa, Anna, Expert Review of Anti-Infective Therapy, Volume 8, Number 1, January 2010, pp. 33-50(18).

Biology and ecology of the brown dog tick, Rhipicephalus sanguineus – Dantas-Torres (2010) “The brown dog tick (Rhipicephalus sanguineus) is the most widespread tick in the world and a well-recognized vector of many pathogens affecting dogs and occasionally humans. This tick can be found on dogs living in both urban and rural areas, being highly adapted to live within human dwellings and being active throughout the year not only in tropical and subtropical regions, but also in some temperate areas. Depending on factors such as climate and host availability, Rh. sanguineus can complete up to four generations per year. Recent studies have demonstrated that ticks exposed to high temperatures attach and feed on humans and rabbits more rapidly. This observation suggests that the risk of human parasitism by Rh. sanguineus could increase in areas experiencing warmer and/or longer summers, consequently increasing the risk of transmission of zoonotic agents (e.g., Rickettsia conorii and Rickettsia rickettsii). In the present article, some aspects of the biology and ecology of Rh. sanguineus ticks are discussed including the possible impact of current climate changes on populations of this tick around the world.” Filipe Dantas-Torres, Parasites & Vectors, Volume 3, Number 1, 26, DOI: 10.1186/1756-3305-3-26. [Full text]

To what extent has climate change contributed to the recent epidemiology of tick-borne diseases? – Randolph (2010) “There is no doubt that all vector-borne diseases are very sensitive to climatic conditions. Many such diseases have shown marked increases in both distribution and incidence during the past few decades, just as human-induced climate change is thought to have exceeded random fluctuations. This coincidence has led to the general perception that climate change has driven disease emergence, but climate change is the inevitable backdrop for all recent events, without implying causality. Coincidence and causality can be disentangled using tick-borne encephalitis (TBE) as a test case, based on the excellent long-term data for this medically significant European disease system. Detailed analysis of climate records since 1970 has revealed abrupt temperature increases just prior to the dramatic upsurge in TBE incidence in many parts of central and eastern Europe. Furthermore, the seasonal patterns of this temperature change are such as might have favoured the transmission of TBE virus between co-feeding ticks. Nevertheless, the pattern of climate change is too uniform to explain the marked heterogeneity in the timing and degree of TBE upsurge, for example in different counties within each of the Baltic countries. Recent decreases as well as increases in TBE incidence must also be taken into account. Instead of a single cause, a network of interacting factors, acting synergistically but with differential force in space and time, would generate this epidemiological heterogeneity. From analysis of past and present events, it appears that human behavioural factors have played a more significant role than purely biological enzootic factors, although there is an explicit causal linkage from one to the other. This includes a range of abiotic and biotic environmental factors, together with human behaviour determined by socio-economic conditions. Many of the abrupt changes followed from the shift from planned to market economies with the fall of Soviet rule. Comparisons between eight countries have indeed revealed a remarkable correlation between poverty indicators and the relative degree of upsurge in TBE from 1993. Against this background of longer-term shifts in TBE incidence, sudden spikes in incidence appear to be due to exceptional weather conditions affecting people’s behaviour, which have a differential impact depending on socio-economic factors. This new perspective may also help explain the epidemiology of Crimean-Congo haemorrhagic fever around the eastern Mediterranean region, including the current exceptional epidemic in Turkey.” Sarah E. Randolph, Veterinary Parasitology, Volume 167, Issues 2-4, 10 February 2010, Pages 92-94, doi:10.1016/j.vetpar.2009.09.011.

Altitudinal patterns of tick and host abundance: a potential role for climate change in regulating tick-borne diseases? – Gilbert (2010) “The impact of climate change on vector-borne infectious diseases is currently controversial. In Europe the primary arthropod vectors of zoonotic diseases are ticks, which transmit Borrelia burgdorferi sensu lato (the agent of Lyme disease), tick-borne encephalitis virus and louping ill virus between humans, livestock and wildlife. Ixodes ricinus ticks and reported tick-borne disease cases are currently increasing in the UK. Theories for this include climate change and increasing host abundance. This study aimed to test how I. ricinus tick abundance might be influenced by climate change in Scotland by using altitudinal gradients as a proxy, while also taking into account the effects of hosts, vegetation and weather effects. It was predicted that tick abundance would be higher at lower altitudes (i.e. warmer climates) and increase with host abundance. Surveys were conducted on nine hills in Scotland, all of open moorland habitat. Tick abundance was positively associated with deer abundance, but even after taking this into account, there was a strong negative association of ticks with altitude. This was probably a real climate effect, with temperature (and humidity, i.e. saturation deficit) most likely playing an important role. It could be inferred that ticks may become more abundant at higher altitudes in response to climate warming. This has potential implications for pathogen prevalence such as louping ill virus if tick numbers increase at elevations where competent transmission hosts (red grouse Lagopus lagopus scoticus and mountain hares Lepus timidus) occur in higher numbers.” Lucy Gilbert, Oecologia, Volume 162, Number 1, 217-225, DOI: 10.1007/s00442-009-1430-x.

Effects of Climate Change on Ticks and Tick-Borne Diseases in Europe – Gray et al. (2009) “Zoonotic tick-borne diseases are an increasing health burden in Europe and there is speculation that this is partly due to climate change affecting vector biology and disease transmission. Data on the vector tick Ixodes ricinus suggest that an extension of its northern and altitude range has been accompanied by an increased prevalence of tick-borne encephalitis. Climate change may also be partly responsible for the change in distribution of Dermacentor reticulatus. Increased winter activity of  I. ricinus is probably due to warmer winters and a retrospective study suggests that hotter summers will change the dynamics and pattern of seasonal activity, resulting in the bulk of the tick population becoming active in the latter part of the year. Climate suitability models predict that eight important tick species are likely to establish more northern permanent populations in a climate-warming scenario. However, the complex ecology and epidemiology of such tick-borne diseases as Lyme borreliosis and tick-borne encephalitis make it difficult to implicate climate change as the main cause of their increasing prevalence. Climate change models are required that take account of the dynamic biological processes involved in vector abundance and pathogen transmission in order to predict future tick-borne disease scenarios.” J. S. Gray, H. Dautel, A. Estrada-Peña, O. Kahl, and E. Lindgren, Interdisciplinary Perspectives on Infectious DiseasesVolume 2009 (2009), Article ID 593232, 12 pages, doi:10.1155/2009/593232. [Full text]

Spatial distribution of Dermacentor reticulatus tick in Slovakia in the beginning of the 21st century – Bullová et al. (2009) “A new field survey monitoring the spatial distribution of Dermacentor (D.) reticulatus (Fabricius, 1794) tick in Slovakia was carried out in 2005–2008 in order to record changes in its distribution when compared to former studies. Last surveys on the geographical distribution were conducted in 1950s and 1970s and the presence of D. reticulatus was determined along the rivers in the south-east (Latorica) as well as in the south-west (Morava, Dunaj) Slovakia. In the present survey new areas with D. reticulatus occurrence were detected, providing evidence that this tick species has extended its range in the surroundings of its former habitats but also by at least 200 km further North and by 300 m of elevation into higher altitudes. D. reticulatus is known to transmit Babesia spp. causing babesiosis in cattle and dogs. Expansion of D. reticulatus range is therefore likely to bring a spread of babesiosis, which can be severe or fatal especially for dogs.” Eva Bullová, Martin Lukáň, Michal Stanko, Branislav Peťko, Veterinary Parasitology, Volume 165, Issues 3-4, 12 November 2009, Pages 357-360, doi:10.1016/j.vetpar.2009.07.023.

Emerging arthropod-borne diseases of companion animals in Europe – Beugnet & Marié (2009) “Vector-borne diseases are caused by parasites, bacteria or viruses transmitted by the bite of hematophagous arthropods (mainly ticks and mosquitoes). The past few years have seen the emergence of new diseases, or re-emergence of existing ones, usually with changes in their epidemiology (i.e. geographical distribution, prevalence, and pathogenicity). The frequency of some vector-borne diseases of pets is increasing in Europe, i.e. canine babesiosis, granulocytic anaplasmosis, canine monocytic ehrlichiosis, thrombocytic anaplasmosis, and leishmaniosis. Except for the last, these diseases are transmitted by ticks. Both the distribution and abundance of the three main tick species, Rhipicephalus sanguineus, Dermacentor reticulatus and Ixodes ricinus are changing. The conditions for such changes involve primarily human factors, such as travel with pets, changes in human habitats, social and leisure activities, but climate changes also have a direct impact on arthropod vectors (abundance, geographical distribution, and vectorial capacity). Besides the most known diseases, attention should be kept on tick-borne encephalitis, which seems to be increasing in western Europe, as well as flea-borne diseases like the flea-transmitted rickettsiosis. Here, after consideration of the main reasons for changes in tick vector ecology, an overview of each “emerging” vector-borne diseases of pets is presented.” Frederic Beugnet, Jean-Lou Marié, Veterinary Parasitology, Volume 163, Issue 4, 26 August 2009, Pages 298-305, doi:10.1016/j.vetpar.2009.03.028. [Full text]

Influence of some climatic factors on Ixodes ricinus ticks studied along altitudinal gradients in two geographic regions in Switzerland – Gern et al. (2008) “In the context of climate change, the seasonal activity of questing Ixodes ricinus and their infection with Borrelia burgdorferi sensu lato (s.l.) were examined in relation to some climatic data along altitudinal gradients in Switzerland. The first study took place in an Alpine area (Valais) from 750 to 1020 m above sea level. The other gradient was located on a mountain in the foothills of the Jura chain (Neuchâtel) from 620 to 1070 m above sea level. In the Alpine area, the highest questing tick density was observed at the highest altitude. At the lowest altitudes (750 and 880 m), very high saturation deficits, >10 mmHg, were present during most of the tick activity season and they seem to have impaired the thriving of tick populations. The second study in Neuchâtel (2003–2005) was a follow-up of a previous study (1999–2001) in which it was observed that tick density decreased with increasing altitude. During the follow-up study, substantial differences in questing tick density and phenology of ticks were observed: At high elevations, questing tick densities were 2.25 and 3.5 times higher for nymphs and adults, respectively, than during 1999–2001. As observed during 1999–2001, questing tick density decreased with increasing altitude in this site in 2003–2005. Tick questing density remained higher at the lowest altitude. Increased temperatures during summer months, more favorable for ticks, reaching values similar to those registered in the first study at the lowest elevations are probably responsible for the higher tick questing density at high altitudes. B. burgdorferi s.l. infection prevalence in ticks decreased with increasing altitudes along both altitudinal gradients. Long-lasting high saturation deficit values may limit the development of tick populations as too high a moisture stress has a negative effect on tick survival. This factor may have a permanent impact, as it is probably the case at the lowest altitudes in the Alpine area or a more transient effect like in the Neuchâtel gradient.” Lise Gern, Francisca Morán Cadenas, Caroline Burri, International Journal of Medical Microbiology, Volume 298, Supplement 1, 1 September 2008, Pages 55-59, doi:10.1016/j.ijmm.2008.01.005. [Full text]

Ixodes ricinus seasonal activity: Implications of global warming indicated by revisiting tick and weather data – Gray (2008) “A recent climate experiment predicted that average maximum summer temperatures in southern regions of the British Isles may approach 30 °C by the year 2020. An opportunity for retrospective analysis of the implications of such a change for tick phenology and disease transmission was presented by the coincidence of unusually high early summer temperatures in 1976 with the collection of tick data from sites in Ireland where host availability was controlled. Subsequent identification of diapause threshold periods and simulation of temperature-dependent tick development showed that high summer temperatures can cause mass transfer of ticks between development cohorts, resulting in increased activity and therefore increased disease transmission in late autumn and early spring. This suggests that in northern temperate regions of Europe global warming is likely to cause changes in the seasonal patterns of tick-borne diseases.” Jeremy S. Gray, International Journal of Medical Microbiology, Volume 298, Supplement 1, 1 September 2008, Pages 19-24, doi:10.1016/j.ijmm.2007.09.005.

Evidence for an increased geographical distribution of Dermacentor reticulatus in Germany and detection of Rickettsia sp. RpA4 – Dautel et al. (2006) “Two studies were performed to elucidate the current distribution of the tick Dermacentor reticulatus in Germany. In the first one in 2003, a total of 365 dogs from 171 sites in the states of Berlin and Brandenburg was screened for ticks, and the corresponding outdoor sites that the dogs usually visited were searched for host-seeking ticks by the flagging method. A total of 1155 ticks was removed from the dogs. The majority were Ixodes ricinus (88.5%), followed by D. reticulatus (9.1%) and I. hexagonus (2.4%). Altogether, 222 dogs carried I. ricinus (60.8%), 41 D. reticulatus (11.2%) and 15 I. hexagonus (4.1%) ticks. Based on scutal index determination, the removed I. ricinus and D. reticulatus had been feeding on the dogs for a mean of 4.0 and 4.5 days, respectively. The dogs infested with D. reticulatus lived at 26 different sites, all previously unknown as Dermacentor sites. Seven of the sites could be confirmed subsequently by flagging the vegetation for ticks. In the second study, a total of 721 deer was shot at 201 different sites from a total of 160 districts all over Germany during the autumn hunting season 2004. A total of 23 deer (3.2%) originating from 14 sites was infested with D. reticulatus. Hereby, significantly more red deer (Cervus elaphus elaphus) than roe deer (Capreolus capreolus) or fallow deer (Dama dama) harboured D. reticulatus ticks. Only two of the sites found had already been known as D. reticulatus areas, whereas all other sites in Brandenburg, Saxony Anhalt, Hesse and Bavaria had been unknown. The results of both studies show that D. reticulatus presently occurs at far more sites than previously known in Germany and thus most likely has expanded its range. Additionally, a total of 135 D. reticulatus removed from deer was screened for Babesia canis and Rickettsia sp. by PCR. A total of 31 D. reticulatus (23%) were positive for Rickettsia. Sequencing revealed in all cases 100% identity with the strain RpA4 that was first isolated from Rhipicephalus ticks in Russia.” Hans Dautel, Cornelia Dippel, Rainer Oehme, Kathrin Hartelt, Elvira Schettler, International Journal of Medical Microbiology, Volume 296, Supplement 1, 22 May 2006, Pages 149-156, doi:10.1016/j.ijmm.2006.01.013.

A dynamic population model to investigate effects of climate on geographic range and seasonality of the tick Ixodes scapularis – Ogden et al. (2005) “A dynamic population model of Ixodes scapularis, the vector of a number of tick-borne zoonoses in North America, was developed to simulate effects of temperature on tick survival and seasonality. Tick development rates were modelled as temperature-dependent time delays, calculated using mean monthly normal temperature data from specific meteorological stations. Temperature also influenced host-finding success in the model. Using data from stations near endemic populations of I. scapularis, the model reached repeatable, stable, cyclical equilibria with seasonal activity of different instars being very close to that observed in the field. In simulations run using data from meteorological stations in central and eastern Canada, the maximum equilibrium numbers of ticks declined the further north was the station location, and simulated populations died out at more northerly stations. Tick die-out at northern latitudes was due to a steady increase in mortality of all life stages with decreasing temperature rather than a specific threshold event in phenology of one life stage. By linear regression we investigated mean annual numbers of degree-days >0 °C (DD>0 °C) as a readily mapped index of the temperature conditions at the meteorological stations providing temperature data for the model. Maximum numbers of ticks at equilibrium were strongly associated with the mean DD>0 °C (r2>0.96, POntario, β=103, P<0.001). The intercepts of the regression models provided theoretical limits for the establishment of I. scapularis in Canada. Maps of these limits suggested that the range of southeast Canada where temperature conditions are currently suitable for the tick, is much wider than the existing distribution of I. scapularis, implying that there is potential for spread. Future applications of the model in investigating climate change effects on I. scapularis are discussed." N.H. Ogden, M. Bigras-Poulin, C.J. O’Callaghan, I.K. Barker, L.R. Lindsay, A. Maarouf, K.E. Smoyer-Tomic, D. Waltner-Toews and D. Charron, International Journal for Parasitology, Volume 35, Issue 4, 1 April 2005, Pages 375-389, doi:10.1016/j.ijpara.2004.12.013. [Full text]

Evidence that climate change has caused ‘emergence’ of tick-borne diseases in Europe? – Randolph (2004) “Even though tick-borne disease systems are highly susceptible to climatic influences, climate change to date is not necessarily the cause of the marked increased incidence of a variety of tick-borne diseases in many parts of Europe over the past two decades. To test for causality, rather than coincidence, we need to examine whether the right sorts of climate change have occurred at the right time and in the right places to account for the observed heterogeneous temporal and spatial patterns of tick-borne disease ‘emergence’. Tick-borne encephalitis (TBE) incidence, for example, showed a 3-fold step increase from 1983 to 1986 in Sweden, doubled in 1993 in the Czech Republic, increased even more dramatically in the same year in Lithuania and Poland, but declined markedly in 1997 in Hungary, Croatia and Slovenia. Within each country, TBE incidence has changed to different degrees in different regions. Because other tick-borne diseases, notably Lyme borreliosis, has commonly ‘emerged’ in parallel with TBE, we should first examine climate variables predicted to have a general effect on tick abundance, which has indeed increased in the past decade. These include temperature and moisture stress, which have seasonally differential impacts. Monthly mean records for 1960–2000 from the UK Climate Research Unit’s interpolated global climate surface reveal that mean spring, spring-autumn and winter temperatures have all increased gradually over the past 40 years, but apparently most sharply in the late 1980s, when moisture stress also increased. These climate data do not reveal any obvious differences between sites where TBE did or did not ‘emerge’, and in Sweden increases in TBE pre-dated the onset of warmer springs and winters. If recorded climate changes cannot yet satisfactorily explain the temporal and spatial patterns of tick-borne disease change in Europe, the impact of biotic factors, such as increases in deer abundance and changing habitat structure, and of socio-political changes following the end of communist rule, demand more detailed quantitative analyses.” Sarah E. Randolph, International Journal of Medical Microbiology Supplements, Volume 293, Supplement 37, April 2004, Pages 5-15, doi:10.1016/S1433-1128(04)80004-4.

A tick-borne encephalitis ceiling in Central Europe has moved upwards during the last 30 years: Possible impact of global warming? – Zeman & Beneš (2004) “The geographic/temporal pattern of cases of tick-borne encephalitis (TBE) registered in the Czech Republic since 1970 was analysed to verify the surmise of a global warming effect. Using a geographic information system, over 8,700 notified places of infection were pinpointed on a map and overlaid with a digital elevation model to estimate the vertical distribution of the cases. Series of yearly disease ceilings (assessed alternatively as the respective maximum altitude or mean altitudes of the upper 5 or 10 cases) were tested against the null hypothesis of random elevation course and analysed for correlation with concomitant factors (yearly TBE incidence rate, mean yearly temperature, population density of small rodents and roe deer). Statistical tests proved that the TBE ceiling has gradually moved upwards in the course of the last three decades. The average rate of ascension within this period was approx. 5.4 ± 1.7 m yearly, which corresponds well with concurrent mean temperature rising of approx. 0.036 ± 0.007°C yearly, and the vertical temperature gradient of 0.0065 ± 0.0004°C m−1. The TBE-ceiling estimates significantly correlated with TBE-incidence data and the mean yearly temperature recorded 1–2 years earlier. Although TBE incidence correlated with rodent population density that was observed 1–2 years earlier, the TBE ceiling does not seem to be influenced by rodent population dynamics nor did the population dynamics correlate with mean yearly temperatures. TBE incidence as well as mean altitudes of the upper 10 cases also correlated with official data on harvested roe deer. Overall, the fluctuations of TBE incidence and TBE ceiling proved to be synchronous processes that correspond with temperature changes. Although the dependence of TBE on temperature is not a direct one and various factors could be involved, an impact of climate warming on the vertical disease distribution in Central Europe is evident.” Petr Zemana and Cestmir Beneš, International Journal of Medical Microbiology Supplements, Volume 293, Supplement 37, April 2004, Pages 48-54, doi:10.1016/S1433-1128(04)80008-1.

Shift of the Tick Ixodes ricinus and Tick-Borne Encephalitis to Higher Altitudes in Central Europe – Daniel et al. (2003) No abstract. M. Daniel, V. Danielová, B. Kříž, A. Jirsa and J. Nožička, European Journal of Clinical Microbiology & Infectious Diseases, Volume 22, Number 5, 327-328, DOI: 10.1007/s10096-003-0918-2.

Tick-borne encephalitis in Sweden and climate change – Lindgren & Gustafson (2001) “Background: The incidence of tick-borne encephalitis (TBE) in Sweden has substantially increased since the mid-1980s. During the same period the climate has become milder and ticks have become more abundant. We investigated whether there is a link between the change in climate and the increase in incidence of TBE. Methods: Since the late 1950s all cases of encephalitis admitted in Stockholm County have been serologically tested for TBE. We analysed the period 1960–98 with multiple regressions. The number of days per season with temperatures of known importance for tick prevalence and pathogen transmission were studied. 2 years of temperature data were related to each TBE incidence rate to account for the tick’s long life-span. Findings: Increases in disease incidence was significantly related (R2=0·58; p<0·0001) to a combination of two consecutive mild winters, temperatures favouring spring development (8–10°C) and extended autumn activity (5–8°C) in the year prior to the incidence year, and temperatures allowing tick activity (5–8°C) early in the incidence year. Interpretations: The findings indicate that the increase in TBE incidence since the mid-1980s is related to the period's change towards milder winters and early arrival of spring. Other factors may have influenced TBE incidence such as more people in endemic locations, and increases in host animal populations; factors which are partly climate related. Access to TBE vaccination since 1986 and increased awareness of ticks might have caused an underestimation of the links found. Our findings also suggest that the incidence of other tick-borne zoonoses might have been affected by the milder climate." Elisabet Lindgren and Rolf Gustafson, The Lancet, Volume 358, Issue 9275, 7 July 2001, Pages 16-18, doi:10.1016/S0140-6736(00)05250-8. [Full text]

Fragile transmission cycles of tick-borne encephalitis virus may be disrupted by predicted climate change – Randolph & Rogers (2000) “Repeated predictions that vector–borne disease prevalence will increase with global warming are usually based on univariate models. Toaccommodate the full range of constraints, the present–day distribution of tick–borne encephalitis virus (TBEv) was matched statistically to current climatic variables, to provide a multivariate description of present–day areas of disease risk. This was then applied to outputs of a general circulation model that predicts how climatic variables may change in the future, and future distributions of TBEv were predicted for them. The expected summer rise in temperature and decrease in moisture appears to drive the distribution of TBEv into higher–latitude and higher–altitude regions progressively through the 2020s, 2050s and 2080s. The final toe–hold in the 2080s may be confined to a small part of Scandinavia, including new foci in southern Finland. The reason for this apparent contraction of the range of TBEv is that its transmission cycles depend on a particular pattern of tick seasonal dynamics, which may be disrupted by climate change. The observed marked increase in incidence of tick–borne encephalitis in most parts of Europe since 1993 may be due to non–biological causes, such as political and sociological changes.” Sarah E. Randolph and David J. Rogers, Proc. R. Soc. Lond. B 7 September 2000 vol. 267 no. 1454 1741-1744, doi: 10.1098/rspb.2000.1204. [Full text]

Impact of climatic change on the northern latitude limit and population density of the disease-transmitting European tick Ixodes ricinus – Lindgren et al. (2000) “We examined whether a reported northward expansion of the geographic distribution limit of the disease-transmitting tick Ixodes ricinus and an increased tick density between the early 1980s and mid-1990s in Sweden was related to climatic changes. The annual number of days with minimum temperatures above vital bioclimatic thresholds for the tick’s life-cycle dynamics were related to tick density in both the early 1980s and the mid-1990s in 20 districts in central and northern Sweden. The winters were markedly milder in all of the study areas in the 1990s as compared to the 1980s. Our results indicate that the reported northern shift in the distribution limit of ticks is related to fewer days during the winter seasons with low minimum temperatures, i.e., below -12 degrees C. At high latitudes, low winter temperatures had the clearest impact on tick distribution. Further south, a combination of mild winters (fewer days with minimum temperatures below -7 degrees C) and extended spring and autumn seasons (more days with minimum temperatures from 5 to 8 degrees C) was related to increases in tick density. We conclude that the relatively mild climate of the 1990s in Sweden is probably one of the primary reasons for the observed increase of density and geographic range of I. ricinus ticks.” E Lindgren, L Tälleklint, and T Polfeldt, Environ Health Perspect. 2000 February; 108(2): 119–123. [Full text]

Seasonal synchrony: the key to tick-borne encephalitis foci identified by satellite data – Randolph et al. (2000) “A previous analysis of tick infestation patterns on rodents in Slovakia suggested that the key to the focal distribution of western-type tick-borne encephalitis virus (TBEv) in Europe is the geographically variable degree of synchrony in the seasonal activity of larval and nymphal Ixodes ricinus ticks. This prediction is here tested by examining records, from 7 different countries, of the seasonal variation in the abundance of larvae and nymphs feeding on rodents or questing on the vegetation. Larvae consistently started feeding and questing earlier in the year at sites within TBEv foci than elsewhere, so that they appeared in the spring as soon as nymphs were active. Such larval–nymphal synchrony is associated with a rapid fall in ground-level temperatures from August to October as revealed by the satellite-derived index of Land Surface Temperature (LST). Likewise, of 1992 pixels sampled on a grid across Europe, the 418 that fell within TBEv foci were characterized by a higher than average rate of autumnal cooling relative to the peak midsummer LST. It is proposed that such a seasonal temperature profile may cause unfed larvae to pass the winter in quiescence, from which they emerge synchronously with nymphs in the spring.” S. E. Randolph, R. M. Green, M. F. Peacey and D. J. Rogers, Parasitology, 2000, 121: 15-23. [Full text]

Ticks and tick-borne disease systems in space and from space – Randolph (2000) “Analyses within geographical information systems (GISs) indicate that small- and large-scale ranges of hard tick species (Ixodidae) are determined more by climate and vegetation than by host-related factors. Spatial distributions of ticks may therefore be analysed by statistical methods that seek correlations between known tick presence/absence and ground- or remotely-sensed (RS) environmental factors. In this way, local habitats of Amblyomma variegatum in the Caribbean and Ixodes ricinus in Europe have been mapped using Landsat RS imagery, while regional and continental distributions of African and temperate tick species have been predicted using multi-temporal information from the National Oceanic and Atmospheric Administration-Advanced Very High Resolution Radiometer (NOAA-AVHRR) imagery. These studies illustrate ways of maximizing statistical accuracy, whose interpretation is then discussed in a biological framework. Methods such as discriminant analysis are biologically transparent and interpretable, while others, such as logistic regression and tree-based classifications, are less so. Furthermore, the most consistently significant variable for predicting tick distributions, the RS Normalized Difference Vegetation Index (NDVI), has a sound biological basis in that it is related to moisture availability to free-living ticks and correlated with tick mortality rates. The development of biological process-based models for predicting the spatial dynamics of ticks is a top priority, especially as the risk of tick-borne infections is commonly related not simply to the vector’s density, but to its seasonal population dynamics. Nevertheless, using statistical pattern-matching, the combination of RS temperature indices and NDVI successfully predicts certain temporal features essential for the transmission of tick-borne encephalitis virus, which translate into a spatial pattern of disease foci on a continental scale.” S.E. Randolph, Advances in Parasitology, Volume 47, 2000, Pages 217-243, Remote Sensing and Geographical Information Systems in Epidemiology, doi:10.1016/S0065-308X(00)47010-7.

Climate and Tickborne Encephalitis – Lindgren (2000) “Climatic changes are projected to alter the abundance, dynamics, and geographical distribution of many vector-borne diseases in human populations. Tick-borne diseases such as Lyme disease and tick-borne encephalitis (TBE) are a growing concern in northern Europe and the United States. The impact of a future climate change on the transmission of tick-borne diseases is not known. To make such assumptions, more empirical data are needed on the relations between short-term fluctuations in contemporary weather and disease incidence. This paper analyzes relations between daily minimum and maximum temperatures, monthly precipitation, and TBE incidence during a 36-yr period in Stockholm County, a high-endemic region for TBE in Sweden. Multiple regression analyses were performed, with temperature variables expressed as number of days per winter or spring – summer – fall season with temperatures above, below, or in the interval between different temperature limits. The limits used for daily minimum temperatures represent bioclimatic thresholds of importance for pathogen transmission. To adjust for the length of the tick’s life cycle, each TBE incidence rate was related to meteorological data over two consecutive years. Results reveal that increased incidence of tick-borne encephalitis is related to a combination of two successive years of more days with temperatures permitting prolonged seasonal tick activity and, hence, pathogen transmission (i.e., daily minimum temperatures above 5ºC-10ºC), and a mild winter preceding the year before the incidence year (i.e., fewer winter days with minimum temperatures below -7ºC). Alternative explanations of the results are discussed. Findings of this study suggest that a climate change may extend the seasonal range and intensify the endemicity of tick-borne diseases, in particular, at northern latitudes.” Elisabet Lindgren. 1998, Conservation Ecology [online] 2(1): 5.. [Full text]

Climate change, tick-borne encephalitis and vaccination needs in Sweden—a prediction model – Lindgren (1998) “A future, global, climate change may indirectly lead to changes in the transmission and incidence of several vector-borne diseases. This paper presents an example of a modeling tool for projections of possible changes in the incidence of tick-borne encephalitis (TBE), and the subsequent changes in vaccination needs, during the next half-century in Sweden. The model is based on the Hadley Center’s regional temperature predictions for the year 2050, taking into account the IPCC IS92 ‘non-intervention scenario’. The model has been constructed into STELLA, a graphical dynamic-simulation, soft-ware program. The model project an increase in TBE incidence in Stockholm County, a high-endemic region in Sweden, during the next 50 years. According to this simplified model, the annual vaccination rate need to increase by 3–4-fold during the next half century in order to prevent the projected increases in TBE incidence in the region from a climatic change.” Elisabet Lindgren, Ecological Modelling, Volume 110, Issue 1, 1 July 1998, Pages 55-63, doi:10.1016/S0304-3800(98)00041-6. [Full text]

Increasing Geographical Distribution and Density of Ixodes ricinus (Acari: Ixodidae) in Central and Northern Sweden – Tälleklint & Jaenson (1998) “The geographical distribution and density of Ixodes ricinus (L.) in the 2 northern regions, Svealand and Norrland, in Sweden were studied by using a questionnaire in Swedish magazines for house owners and dog owners, and in provincial newspapers. Analysis of the ≍1,200 answers revealed that ticks are present in all parts of Svealand (except northern Varmland and northern and western Dalarna), the southeastern part of Norrland (i.e., Gästrikland and Hälsingland), and along the Baltic Sea coast of central and northern Norrland. The proportion of answers reporting ticks and the estimated tick density (i.e., the number of ticks infesting dogs and cats) decreased from south to north. The answers to the questionnaire and data from field sampling of ticks suggest that tick density decreased distinctly along a narrow boundary zone, coinciding with the biological limit of Norrland (Limes Norrlandicus), crossing Sweden through southern Varmland, southeastern Dalarna, and central Gastrikland. The results of the questionnaire suggest that I. ricinus ticks are more widespread today than in the early 1980s, especially in Varmland, western and central Dalarna, Hiilsingland, and the coastal areas of Medelpad, Angermanland, and Vasterbotten, and that the proportion of the human population at risk for tick-borne pathogens in Svealand and Norrland is increasing.” Tälleklint, Lars; Jaenson, Thomas G. T., Journal of Medical Entomology, Volume 35, Number 4, July 1998 , pp. 521-526(6).

Geographical Distribution, Host Associations, and Vector Roles of Ticks (Acari: Ixodidae, Argasidae) in Sweden – Jaenson et al. (1994) “This review covers the geographic distribution and host relationships of the tick species in Sweden. Ixodes uriae White, I. caledonicus Nuttall, I. unicavatus Neumann, I. arboricola Schulze & Schlottke, and I. lividus Koch are ornithophagous species. I. trianguliceps Birula, I. canisuga Johnston, I. hexagonus Leach, and Argas vespertilionis (Latreille) are mammalophagous. I. ricinus (L.) and Haemaphysails punctata Canestrini & Fanzago feed on both birds and mammals. All these tick species may be considered to be permanently present in Sweden. I. persulcatus Schulze, Hyalomma marginatum Koch, and the brown dog tick, Rhipicephalus satiguineus (Latreille), may be regarded as not indigenous to Sweden although they may be regularly introduced by spring-migrating birds or imported dogs, respectively. The first European record of the American dog tick, Dermacentor variabilis (Say), is reported. There are several records of Hyalomma aegyptium (L.) from imported tortoises in Sweden. Excluding other ticks imported on exotic pets and zoo animals, another 13 tick species are listed that may occur, at least occasionally, in Sweden. Because of its wide geographic distribution, great abundance, and wide host range, I. ricinus is medically the most important arthropod in northern Europe. I. ricinus is common in southern and south-central Sweden and along the coast of northern Sweden and has been recorded from 29 mammal species, 56 bird species, and two species of lizards in Sweden alone. The potential introduction to Sweden of exotic pathogens with infected ticks (e.g., I. persulcatus and H. marginatum on birds or Dermacentor spp. and R. sanguineus on mammals) is evident.” Jaenson, Thomas G. T., Tälleklint, Lars, Lundqvist, Lars, Olsen, Björn, Chirico, Jan, Mejlon, Hans, Journal of Medical Entomology, Volume 31, Number 2, March 1994 , pp. 240-256(17).

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Papers on amphibian decline

Posted by Ari Jokimäki on August 3, 2011

This is a list of papers on recent decline and extinctions in amphibian populations. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (August 4, 2011): Anchukaitis & Evans (2010) [pointed out to me in Twitter by Kevin Anchukaitis] Duarte et al. (2011) [was published today] added.

Can amphibians take the heat? Vulnerability to climate warming in subtropical and temperate larval amphibian communities – Duarte et al. (2011) “Predicting the biodiversity impacts of global warming implies we know where and with what magnitude these impacts will be encountered. Amphibians are currently the most threatened vertebrates, mainly due to habitat loss and to emerging infectious diseases. Global warming may further exacerbate their decline in the near future, although the impact might vary geographically. We predicted that subtropical amphibians should be relatively susceptible to warming induced extinctions because their upper critical thermal limits (CTmax) might be only slightly higher than maximum pond temperatures (Tmax). We tested this prediction by measuring CTmax and Tmax for 47 larval amphibian species from two thermally distinct subtropical communities (the warm community of the Gran Chaco and the cool community of Atlantic Forest, northern Argentina), as well as from one European temperate community. Upper thermal tolerances of tadpoles were positively correlated (controlling for phylogeny) with maximum pond temperatures, although the slope was steeper in subtropical than in temperate species. CTmax values were lowest in temperate species and highest in the subtropical warm community, which paradoxically, had very low warming tolerance (CTmax – Tmax) and therefore may be prone to future local extinction from acute thermal stress if rising pond Tmax soon exceeds their CTmax. Canopy protected subtropical cool species have larger warming tolerance and thus should be less impacted by peak temperatures. Temperate species are relatively secure to warming impacts, except for late breeders with low thermal tolerance which may be exposed to physiological thermal stress in the coming years.” Helder Duarte, Miguel Tejedo, Marco Katzenberger, Federico Marangoni, Diego Baldo, Juan Francisco Beltrán, Dardo Andrea Martí, Alex Richter-Boix, Alejandro Gonzalez-Voyer, Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02518.x.

Citation Rate and Perceived Subject Bias in the Amphibian-Decline Literature – Ohmer & Bishop (2011) “As a result of global declines in amphibian populations, interest in the conservation of amphibians has grown. This growth has been fueled partially by the recent discovery of other potential causes of declines, including chytridiomycosis (the amphibian chytrid, an infectious disease) and climate change. It has been proposed that researchers have shifted their focus to these novel stressors and that other threats to amphibians, such as habitat loss, are not being studied in proportion to their potential effects. We tested the validity of this proposal by reviewing the literature on amphibian declines, categorizing the primary topic of articles within this literature (e.g., habitat loss or UV-B radiation) and comparing citation rates among articles on these topics and impact factors of journals in which the articles were published. From 1990 to 2009, the proportion of papers on habitat loss remained fairly constant, and although the number of papers on chytridiomycosis increased after the disease was described in 1998, the number of published papers on amphibian declines also increased. Nevertheless, papers on chytridiomycosis were more highly cited than papers not on chytridiomycosis and were published in journals with higher impact factors on average, which may indicate this research topic is more popular in the literature. Our results were not consistent with a shift in the research agenda on amphibians. We believe the perception of such a shift has been supported by the higher citation rates of papers on chytridiomycosis.” Michel E. Ohmer, Phillip J. Bishop, Conservation Biology, Volume 25, Issue 1, pages 195–199, February 2011, DOI: 10.1111/j.1523-1739.2010.01591.x. [Full text, Supporting information Note that SI has a spreadsheet with references to about 1500 papers on the subject!]

Amphibian decline and extinction: What we know and what we need to learn – Collins (2010) “For over 350 million yr, thousands of amphibian species have lived on Earth. Since the 1980s, amphibians have been disappearing at an alarming rate, in many cases quite suddenly. What is causing these declines and extinctions? In the modern era (post 1500) there are 6 leading causes of biodiversity loss in general, and all of these acting alone or together are responsible for modern amphibian declines: commercial use; introduced/exotic species that compete with, prey on, and parasitize native frogs and salamanders; land use change; contaminants; climate change; and infectious disease. The first 3 causes are historical in the sense that they have been operating for hundreds of years, although the rate of change due to each accelerated greatly after about the mid-20th century. Contaminants, climate change, and emerging infectious diseases are modern causes suspected of being responsible for the so-called ‘enigmatic decline’ of amphibians in protected areas. Introduced/exotic pathogens, land use change, and infectious disease are the 3 causes with a clear role in amphibian decline as well as extinction; thus far, the other 3 causes are only implicated in decline and not extinction. The present work is a review of the 6 causes with a focus on pathogens and suggested areas where new research is needed. Batrachochytrium dendrobatidis (Bd) is a chytrid fungus that is an emerging infectious disease causing amphibian population decline and species extinction. Historically, pathogens have not been seen as a major cause of extinction, but Bd is an exception, which is why it is such an interesting, important pathogen to understand. The late 20th and early 21st century global biodiversity loss is characterized as a sixth extinction event. Amphibians are a striking example of these losses as they disappear at a rate that greatly exceeds historical levels. Consequently, modern amphibian decline and extinction is a lens through which we can view the larger story of biodiversity loss and its consequences.” James P. Collins, Dis Aquat Org 92:93-99, doi:10.3354/dao02307.

Tropical cloud forest climate variability and the demise of the Monteverde golden toad – Anchukaitis & Evans (2010) “Widespread amphibian extinctions in the mountains of the American tropics have been blamed on the interaction of anthropogenic climate change and a lethal pathogen. However, limited meteorological records make it difficult to conclude whether current climate conditions at these sites are actually exceptional in the context of natural variability. We use stable oxygen isotope measurements from trees without annual rings to reconstruct a century of hydroclimatology in the Monteverde Cloud Forest of Costa Rica. High-resolution measurements reveal coherent isotope cycles that provide annual chronological control and paleoclimate information. Climate variability is dominated by interannual variance in dry season moisture associated with El Niño Southern Oscillation events. There is no evidence of a trend associated with global warming. Rather, the extinction of the Monteverde golden toad (Bufo periglenes) appears to have coincided with an exceptionally dry interval caused by the 1986–1987 El Niño event.” Kevin J. Anchukaitis and Michael N. Evans, PNAS March 16, 2010 vol. 107 no. 11 5036-5040, doi: 10.1073/pnas.0908572107. [Full text]

Global Amphibian Extinction Risk Assessment for the Panzootic Chytrid Fungus – Rödder et al. (2009) “Species are being lost at increasing rates due to anthropogenic effects, leading to the recognition that we are witnessing the onset of a sixth mass extinction. Emerging infectious disease has been shown to increase species loss and any attempts to reduce extinction rates need to squarely confront this challenge. Here, we develop a procedure for identifying amphibian species that are most at risk from the effects of chytridiomycosis by combining spatial analyses of key host life-history variables with the pathogen’s predicted distribution. We apply our rule set to the known global diversity of amphibians in order to prioritize pecies that are most at risk of loss from disease emergence. This risk assessment shows where limited conservation funds are best deployed in order to prevent further loss of species by enabling ex situ amphibian salvage operations and focusing any potential disease mitigation projects.” Dennis Rödder, Jos Kielgast, Jon Bielby, Sebastian Schmidtlein, Jaime Bosch, Trenton W. J. Garner, Michael Veith, Susan Walker, Matthew C. Fisher and Stefan Lötters, Diversity 2009, 1(1), 52-66; doi:10.3390/d1010052. [Full text]

Chytridiomycosis, Amphibian Extinctions, and Lessons for the Prevention of Future Panzootics – Kriger & Hero (2009) “The human-mediated transport of infected amphibians is the most plausible driver for the intercontinental spread of chytridiomycosis, a recently emerged infectious disease responsible for amphibian population declines and extinctions on multiple continents. Chytridiomycosis is now globally ubiquitous, and it cannot be eradicated from affected sites. Its rapid spread both within and between continents provides a valuable lesson on preventing future panzootics and subsequent erosion of biodiversity, not only of amphibians, but of a wide array of taxa: the continued inter-continental trade and transport of animals will inevitably lead to the spread of novel pathogens, followed by numerous extinctions. Herein, we define and discuss three levels of amphibian disease management: (1) post-exposure prophylactic measures that are curative in nature and applicable only in a small number of situations; (2) pre-exposure prophylactic measures that reduce disease threat in the short-term; and (3) preventive measures that remove the threat altogether. Preventive measures include a virtually complete ban on all unnecessary long-distance trade and transport of amphibians, and are the only method of protecting amphibians from disease-induced declines and extinctions over the long-term. Legislation to prevent the emergence of new diseases is urgently required to protect global amphibian biodiversity.” Kerry M. Kriger and Jean-Marc Hero, EcoHealth, Volume 6, Number 1, 6-10, DOI: 10.1007/s10393-009-0228-y. [Full text]

Are we in the midst of the sixth mass extinction? A view from the world of amphibians – Wake & Vredenburg (2008) “Many scientists argue that we are either entering or in the midst of the sixth great mass extinction. Intense human pressure, both direct and indirect, is having profound effects on natural environments. The amphibians—frogs, salamanders, and caecilians—may be the only major group currently at risk globally. A detailed worldwide assessment and subsequent updates show that one-third or more of the 6,300 species are threatened with extinction. This trend is likely to accelerate because most amphibians occur in the tropics and have small geographic ranges that make them susceptible to extinction. The increasing pressure from habitat destruction and climate change is likely to have major impacts on narrowly adapted and distributed species. We show that salamanders on tropical mountains are particularly at risk. A new and significant threat to amphibians is a virulent, emerging infectious disease, chytridiomycosis, which appears to be globally distributed, and its effects may be exacerbated by global warming. This disease, which is caused by a fungal pathogen and implicated in serious declines and extinctions of >200 species of amphibians, poses the greatest threat to biodiversity of any known disease. Our data for frogs in the Sierra Nevada of California show that the fungus is having a devastating impact on native species, already weakened by the effects of pollution and introduced predators. A general message from amphibians is that we may have little time to stave off a potential mass extinction.” David B. Wake and Vance T. Vredenburg, PNAS August 12, 2008 vol. 105 no. Supplement 1 11466-11473, doi: 10.1073/pnas.0801921105. [Full text]

Evaluating the links between climate, disease spread, and amphibian declines – Rohr et al. (2008) “Human alteration of the environment has arguably propelled the Earth into its sixth mass extinction event and amphibians, the most threatened of all vertebrate taxa, are at the forefront. Many of the worldwide amphibian declines have been caused by the chytrid fungus, Batrachochytrium dendrobatidis (Bd), and two contrasting hypotheses have been proposed to explain these declines. Positive correlations between global warming and Bd-related declines sparked the chytrid-thermal-optimum hypothesis, which proposes that global warming increased cloud cover in warm years that drove the convergence of daytime and nighttime temperatures toward the thermal optimum for Bd growth. In contrast, the spatiotemporal-spread hypothesis states that Bd-related declines are caused by the introduction and spread of Bd, independent of climate change. We provide a rigorous test of these hypotheses by evaluating (i) whether cloud cover, temperature convergence, and predicted temperature-dependent Bd growth are significant positive predictors of amphibian extinctions in the genus Atelopus and (ii) whether spatial structure in the timing of these extinctions can be detected without making assumptions about the location, timing, or number of Bd emergences. We show that there is spatial structure to the timing of Atelopus spp. extinctions but that the cause of this structure remains equivocal, emphasizing the need for further molecular characterization of Bd. We also show that the reported positive multi-decade correlation between Atelopus spp. extinctions and mean tropical air temperature in the previous year is indeed robust, but the evidence that it is causal is weak because numerous other variables, including regional banana and beer production, were better predictors of these extinctions. Finally, almost all of our findings were opposite to the predictions of the chytrid-thermal-optimum hypothesis. Although climate change is likely to play an important role in worldwide amphibian declines, more convincing evidence is needed of a causal link.” Jason R. Rohr, Thomas R. Raffel, John M. Romansic, Hamish McCallum, and Peter J. Hudson, PNAS November 11, 2008 vol. 105 no. 45 17436-17441, doi: 10.1073/pnas.0806368105. [Full text]

Life-history trade-offs influence disease in changing climates: strategies of an amphibian pathogen – Woodhams et al. (2008) “Life-history trade-offs allow many animals to maintain reproductive fitness across a range of climatic conditions. When used by parasites and pathogens, these strategies may influence patterns of disease in changing climates. The chytrid fungus, Batrachochytrium dendrobatidis, is linked to global declines of amphibian populations. Short-term growth in culture is maximal at 17°–25°C. This has been used in an argument that global warming, which increases the time that amphibians spend at these temperatures in cloud-covered montane environments, has led to extinctions. Here we show that the amphibian chytrid responds to decreasing temperatures with trade-offs that increase fecundity as maturation rate slows and increase infectivity as growth decreases. At 17°–25°C, infectious zoospores encyst (settle and develop a cell wall) and develop into the zoospore-producing stage (zoosporangium) faster, while at 7°–10°C, greater numbers of zoospores are produced per zoosporangium; these remain infectious for a longer period of time. We modeled the population growth of B. dendrobatidis through time at various temperatures using delayed differential equations and observational data for four parameters: developmental rate of thalli, fecundity, rate of zoospore encystment, and rate of zoospore survival. From the models, it is clear that life-history trade-offs allow B. dendrobatidis to maintain a relatively high long-term growth rate at low temperatures, so that it maintains high fitness across a range of temperatures. When a seven-day cold shock is simulated, the outcome is intermediate between the two constant temperature regimes, and in culture, a sudden drop in temperature induces zoospore release. These trade-offs can be ecologically important for a variety of organisms with complex life histories, including pathogenic microorganisms. The effect of temperature on amphibian mortality will depend on the interaction between fungal growth and host immune function and will be modified by host ecology, behavior, and life history. These results demonstrate that B. dendrobatidis populations can grow at high rates across a broad range of environmental temperatures and help to explain why it is so successful in cold montane environments.” Woodhams, Douglas C., Ross A. Alford, Cheryl J. Briggs, Megan Johnson, and Louise A. Rollins-Smith. 2008, Ecology 89:1627–1639. [doi:10.1890/06-1842.1]. [Full text]

Measuring the Meltdown: Drivers of Global Amphibian Extinction and Decline – Sodhi et al. (2008) “Habitat loss, climate change, over-exploitation, disease and other factors have been hypothesised in the global decline of amphibian biodiversity. However, the relative importance of and synergies among different drivers are still poorly understood. We present the largest global analysis of roughly 45% of known amphibians (2,583 species) to quantify the influences of life history, climate, human density and habitat loss on declines and extinction risk. Multi-model Bayesian inference reveals that large amphibian species with small geographic range and pronounced seasonality in temperature and precipitation are most likely to be Red-Listed by IUCN. Elevated habitat loss and human densities are also correlated with high threat risk. Range size, habitat loss and more extreme seasonality in precipitation contributed to decline risk in the 2,454 species that declined between 1980 and 2004, compared to species that were stable (n=1,545) or had increased (n=28). These empirical results show that amphibian species with restricted ranges should be urgently targeted for conservation.” Navjot S. Sodhi, David Bickford, Arvin C. Diesmos, Tien Ming Lee, Lian Pin Koh, Barry W. Brook, Cagan H. Sekercioglu, and Corey J. A. Bradshaw, PLoS ONE. 2008; 3(2): e1636, doi: 10.1371/journal.pone.0001636. [Full text]

Global warming and amphibian extinctions in eastern Australia – Laurance (2008) “Pounds et al. recently argued that the dramatic, fungal pathogen-linked extinctions of numerous harlequin frogs (Atelopus spp.) in upland rainforests of South America mostly occurred immediately following exceptionally warm years, implicating global warming as a likely trigger for these extinctions. I tested this hypothesis using temperature data for eastern Australia, where at least 14 upland-rainforest frog species have also experienced extinctions or striking population declines attributed to the same fungal pathogen, and where temperatures have also risen significantly in recent decades. My analyses provide little direct support for the warm-year hypothesis of Pounds et al., although my statistical power to detect effects of small (0.5°C) temperature increases was limited. However, I found stronger support for a modified version of the warm-year hypothesis, whereby frog declines were likely to occur following three consecutive years of unusually warm weather. This trend was apparent only at tropical latitudes, where rising minimum temperatures were greatest. Although much remains uncertain, my findings appear consistent with the notion that global warming could predispose some upland amphibian populations to virulent pathogens.” William F. Laurance, Austral Ecology, Volume 33, Issue 1, pages 1–9, February 2008, DOI: 10.1111/j.1442-9993.2007.01812.x. [Full text]

Riding the Wave: Reconciling the Roles of Disease and Climate Change in Amphibian Declines – Lips et al. (2008) “We review the evidence for the role of climate change in triggering disease outbreaks of chytridiomycosis, an emerging infectious disease of amphibians. Both climatic anomalies and disease-related extirpations are recent phenomena, and effects of both are especially noticeable at high elevations in tropical areas, making it difficult to determine whether they are operating separately or synergistically. We compiled reports of amphibian declines from Lower Central America and Andean South America to create maps and statistical models to test our hypothesis of spatiotemporal spread of the pathogen Batrachochytrium dendrobatidis (Bd), and to update the elevational patterns of decline in frogs belonging to the genus Atelopus. We evaluated claims of climate change influencing the spread of Bd by including error into estimates of the relationship between air temperature and last year observed. Available data support the hypothesis of multiple introductions of this invasive pathogen into South America and subsequent spread along the primary Andean cordilleras. Additional analyses found no evidence to support the hypothesis that climate change has been driving outbreaks of amphibian chytridiomycosis, as has been posited in the climate-linked epidemic hypothesis. Future studies should increase retrospective surveys of museum specimens from throughout the Andes and should study the landscape genetics of Bd to map fine-scale patterns of geographic spread to identify transmission routes and processes.” Karen R. Lips, Jay Diffendorfer, Joseph R. Mendelson III, Michael W. Sears, PLoS Biol 6(3): e72. doi:10.1371/journal.pbio.0060072. [Full text]

Amphibian Decline or Extinction? Current Declines Dwarf Background Extinction Rate – McCallum (2007) “Amphibian declines and extinctions are critical concerns of biologists around the world. The estimated current rate of amphibian extinction is known, but how it compares to the background amphibian extinction rate from the fossil record has not been well studied. I compared current amphibian extinction rates with their reported background extinction rates using standard and fuzzy arithmetic. These calculations suggest that the current extinction rate of amphibians could be 211 times the background amphibian extinction rate. If current estimates of amphibian species in imminent danger of extinction are included in these calculations, then the current amphibian extinction rate may range from 25,039–45,474 times the background extinction rate for amphibians. It is difficult to explain this unprecedented and accelerating rate of extinction as a natural phenomenon.” Malcolm L. McCallum, Journal of Herpetology 41(3):483-491. 2007, doi: 10.1670/0022-1511(2007)41[483:ADOECD]2.0.CO;2. [Full text]

Spread of Chytridiomycosis Has Caused the Rapid Global Decline and Extinction of Frogs – Skerratt et al. (2007) “The global emergence and spread of the pathogenic, virulent, and highly transmissible fungus Batrachochytrium dendrobatidis, resulting in the disease chytridiomycosis, has caused the decline or extinction of up to about 200 species of frogs. Key postulates for this theory have been completely or partially fulfilled. In the absence of supportive evidence for alternative theories despite decades of research, it is important for the scientific community and conservation agencies to recognize and manage the threat of chytridiomycosis to remaining species of frogs, especially those that are naive to the pathogen. The impact of chytridiomycosis on frogs is the most spectacular loss of vertebrate biodiversity due to disease in recorded history.” Lee Francis Skerratt, Lee Berger, Richard Speare, Scott Cashins, Keith Raymond McDonald, Andrea Dawn Phillott, Harry Bryan Hines and Nicole Kenyon, EcoHealth, Volume 4, Number 2, 125-134, DOI: 10.1007/s10393-007-0093-5. [Full text]

Widespread amphibian extinctions from epidemic disease driven by global warming – Pounds et al. (2006) “As the Earth warms, many species are likely to disappear, often because of changing disease dynamics. Here we show that a recent mass extinction associated with pathogen outbreaks is tied to global warming. Seventeen years ago, in the mountains of Costa Rica, the Monteverde harlequin frog (Atelopus sp.) vanished along with the golden toad (Bufo periglenes). An estimated 67% of the 110 or so species of Atelopus, which are endemic to the American tropics, have met the same fate, and a pathogenic chytrid fungus (Batrachochytrium dendrobatidis) is implicated. Analysing the timing of losses in relation to changes in sea surface and air temperatures, we conclude with ‘very high confidence’ (> 99%, following the Intergovernmental Panel on Climate Change, IPCC) that large-scale warming is a key factor in the disappearances. We propose that temperatures at many highland localities are shifting towards the growth optimum of Batrachochytrium, thus encouraging outbreaks. With climate change promoting infectious disease and eroding biodiversity, the urgency of reducing greenhouse-gas concentrations is now undeniable.” J. Alan Pounds, Martín R. Bustamante, Luis A. Coloma, Jamie A. Consuegra, Michael P. L. Fogden, Pru N. Foster, Enrique La Marca, Karen L. Masters, Andrés Merino-Viteri, Robert Puschendorf, Santiago R. Ron, G. Arturo Sánchez-Azofeifa, Christopher J. Still & Bruce E. Young, Nature 439, 161-167 (12 January 2006) | doi:10.1038/nature04246. [Full text]

Emerging infectious disease and the loss of biodiversity in a Neotropical amphibian community – Lips et al. (2006) “Pathogens rarely cause extinctions of host species, and there are few examples of a pathogen changing species richness and diversity of an ecological community by causing local extinctions across a wide range of species. We report the link between the rapid appearance of a pathogenic chytrid fungus Batrachochytrium dendrobatidis in an amphibian community at El Copé, Panama, and subsequent mass mortality and loss of amphibian biodiversity across eight families of frogs and salamanders. We describe an outbreak of chytridiomycosis in Panama and argue that this infectious disease has played an important role in amphibian population declines. The high virulence and large number of potential hosts of this emerging infectious disease threaten global amphibian diversity.” Karen R. Lips, Forrest Brem, Roberto Brenes, John D. Reeve, Ross A. Alford, Jamie Voyles, Cynthia Carey, Lauren Livo, Allan P. Pessier, and James P. Collins, PNAS February 28, 2006 vol. 103 no. 9 3165-3170, doi: 10.1073/pnas.0506889103. [Full text]

Species Review of Amphibian Extinction Risks in Madagascar: Conclusions from the Global Amphibian Assessment – Andreone et al. (2005) “We assessed the extinction risks of Malagasy amphibians by evaluating their distribution, occurrence in protected areas, population trends, habitat quality, and prevalence in commercial trade. We estimated and mapped the distribution of each of the 220 described Malagasy species and applied, for the first time, the IUCN Red List categories and criteria to all species described at the time of the assessment. Nine species were categorized as critically endangered, 21 as endangered, and 25 as vulnerable. The most threatened species occur on the High Plateau and/or have been subjected to overcollection for the pet trade, but restricted extent of occurrence and ongoing habitat destruction were identified as the most important factors influencing extinction threats. The two areas with the majority of threatened species were the northern Tsaratanana-Marojejy-Masoala highlands and the southeastern Anosy Mountains. The current system of protected areas includes 82% of the threatened amphibian species. Of the critically endangered species, 6 did not occur in any protected area. For conservation of these species we recommend the creation of a reserve for the species of the Mantella aurantiaca group, the inclusion of two Scaphiophryne species in the Convention on the International Trade in Endangered Species Appendix II, and the suspension of commercial collecting for Mantella cowani. Field surveys during the last 15 years reveal no pervasive extinction of Malagasy amphibians resulting from disease or other agents, as has been reported in some other areas of the world.” Franco Andreone, John E. Cadle, Neil Cox, Frank Glaw, Ronald A. Nussbaum, Christopher J. Raxworthy, Simon N. Stuart, Denis Vallan, Miguel Vences, Conservation Biology, Volume 19, Issue 6, pages 1790–1802, December 2005, DOI: 10.1111/j.1523-1739.2005.00249.x. [Full text]

Status and Trends of Amphibian Declines and Extinctions Worldwide – Stuart et al. (2004) “The first global assessment of amphibians provides new context for the well-publicized phenomenon of amphibian declines. Amphibians are more threatened and are declining more rapidly than either birds or mammals. Although many declines are due to habitat loss and overutilization, other, unidentified processes threaten 48% of rapidly declining species and are driving species most quickly to extinction. Declines are nonrandom in terms of species’ ecological preferences, geographic ranges, and taxonomic associations and are most prevalent among Neotropical montane, stream-associated species. The lack of conservation remedies for these poorly understood declines means that hundreds of amphibian species now face extinction.” Simon N. Stuart, Janice S. Chanson, Neil A. Cox, Bruce E. Young, Ana S. L. Rodrigues, Debra L. Fischman and Robert W. Waller, Science 3 December 2004: Vol. 306 no. 5702 pp. 1783-1786, DOI: 10.1126/science.1103538. [Full text]

Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America – Berger et al. (1998) “Epidermal changes caused by a chytridiomycete fungus (Chytridiomycota; Chytridiales) were found in sick and dead adult anurans collected from montane rain forests in Queensland (Australia) and Panama during mass mortality events associated with significant population declines. We also have found this new disease associated with morbidity and mortality in wild and captive anurans from additional locations in Australia and Central America. This is the first report of parasitism of a vertebrate by a member of the phylum Chytridiomycota. Experimental data support the conclusion that cutaneous chytridiomycosis is a fatal disease of anurans, and we hypothesize that it is the proximate cause of these recent amphibian declines.” Lee Berger, Rick Speare, Peter Daszak, D. Earl Green, Andrew A. Cunningham, C. Louise Goggin, Ron Slocombe, Mark A. Ragan, Alex D. Hyatt, Keith R. McDonald, Harry B. Hines, Karen R. Lips, Gerry Marantelli, and Helen Parkes, PNAS July 21, 1998 vol. 95 no. 15 9031-9036. [Full text]

Amphibian Declines: Judging Stability, Persistence, and Susceptibility of Populations to Local and Global Extinctions – Blaustein et al. (1994) “Extinctions are normal biological phenomena. Both mass extinctions in geological time and local extinctions in ecological time are well documented, but rates of extinction have increased in recent years – especially in vertebrates, including amphibians – as illustrated by recent reports of their population declines and range reductions. We suggest that long-term population data are necessary for rigorously evaluating the significance of the amphibian declines. Due to the physiological constraints, relatively low mobility, and site fidelity of amphibians, we suggest that many amphibian populations may be unable to recolonize areas after local extinction.” Andrew R. Blaustein, David B. Wake and Wayne P. Sousa, Conservation Biology, Vol. 8, No. 1 (Mar., 1994), pp. 60-71. [Full text]

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Papers on coral response to global warming

Posted by Ari Jokimäki on February 24, 2011

This is a list of papers on coral response to global warming and the ocean acidification. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Rapid poleward range expansion of tropical reef corals in response to rising sea surface temperatures – Yamano et al. (2011) “Rising temperatures caused by climatic warming may cause poleward range shifts and/or expansions in species distribution. Tropical reef corals (hereafter corals) are some of the world’s most important species, being not only primary producers, but also habitat-forming species, and thus fundamental ecosystem modification is expected according to changes in their distribution. Although most studies of climate change effects on corals have focused on temperature-induced coral bleaching in tropical areas, poleward range shifts and/or expansions may also occur in temperate areas. We show the first large-scale evidence of the poleward range expansion of modern corals, based on 80 years of national records from the temperate areas of Japan, where century-long measurements of in situ sea-surface temperatures have shown statistically significant rises. Four major coral species categories, including two key species for reef formation in tropical areas, showed poleward range expansions since the 1930s, whereas no species demonstrated southward range shrinkage or local extinction. The speed of these expansions reached up to 14 km/year, which is far greater than that for other species. Our results, in combination with recent findings suggesting range expansions of tropical coral-reef associated organisms, strongly suggest that rapid, fundamental modifications of temperate coastal ecosystems could be in progress.” Yamano, H., K. Sugihara, and K. Nomura (2011), Geophys. Res. Lett., 38, L04601, doi:10.1029/2010GL046474.

Modeling regional coral reef responses to global warming and changes in ocean chemistry: Caribbean case study – Buddemeier et al. (2011) “Climatic change threatens the future of coral reefs in the Caribbean and the important ecosystem services they provide. We used a simulation model [Combo (“COral Mortality and Bleaching Output”)] to estimate future coral cover in the part of the eastern Caribbean impacted by a massive coral bleaching event in 2005. Combo calculates impacts of future climate change on coral reefs by combining impacts from long-term changes in average sea surface temperature (SST) and ocean acidification with impacts from episodic high temperature mortality (bleaching) events. We used mortality and heat dose data from the 2005 bleaching event to select historic temperature datasets, to use as a baseline for running Combo under different future climate scenarios and sets of assumptions. Results suggest a bleak future for coral reefs in the eastern Caribbean. For three different emissions scenarios from the Intergovernmental Panel on Climate Change (IPCC; B1, A1B, and A1FI), coral cover on most Caribbean reefs is projected to drop below 5% by the year 2035, if future mortality rates are equivalent to some of those observed in the 2005 event (50%). For a scenario where corals gain an additional 1–1.5°C of heat tolerance through a shift in the algae that live in the coral tissue, coral cover above 5% is prolonged until 2065. Additional impacts such as storms or anthropogenic damage could result in declines in coral cover even faster than those projected here. These results suggest the need to identify and preserve the locations that are likely to have a higher resiliency to bleaching to save as many remnant populations of corals as possible in the face of projected wide-spread coral loss.” R. W. Buddemeier, Diana R. Lane and J. A. Martinich, Climatic Change, DOI: 10.1007/s10584-011-0022-z. [full text]

Coral reefs may start dissolving when atmospheric CO2 doubles – Silverman et al. (2009) “Calcification rates in stony corals are expected to decline significantly in the near future due to ocean acidification. In this study we provide a global estimate of the decline in calcification of coral reefs as a result of increase in sea surface temperature and partial pressure of CO2. This estimate, unlike previously reported estimates, is based on an empirical rate law developed from field observations for gross community calcification as a function of aragonite degree of saturation (Ωarag), sea surface temperature and live coral cover. Calcification rates were calculated for more than 9,000 reef locations using model values of Ωarag and sea surface temperature at different levels of atmospheric CO2. The maps we produced show that by the time atmospheric partial pressure of CO2 will reach 560 ppm all coral reefs will cease to grow and start to dissolve.” Silverman, J., B. Lazar, L. Cao, K. Caldeira, and J. Erez (2009), Geophys. Res. Lett., 36, L05606, doi:10.1029/2008GL036282. [full text]

Climate change and coral reef bleaching: An ecological assessment of long-term impacts, recovery trends and future outlook – Baker et al. (2008) “Since the early 1980s, episodes of coral reef bleaching and mortality, due primarily to climate-induced ocean warming, have occurred almost annually in one or more of the world’s tropical or subtropical seas. Bleaching is episodic, with the most severe events typically accompanying coupled ocean–atmosphere phenomena, such as the El Niño-Southern Oscillation (ENSO), which result in sustained regional elevations of ocean temperature. Using this extended dataset (25+ years), we review the short- and long-term ecological impacts of coral bleaching on reef ecosystems, and quantitatively synthesize recovery data worldwide. Bleaching episodes have resulted in catastrophic loss of coral cover in some locations, and have changed coral community structure in many others, with a potentially critical influence on the maintenance of biodiversity in the marine tropics. Bleaching has also set the stage for other declines in reef health, such as increases in coral diseases, the breakdown of reef framework by bioeroders, and the loss of critical habitat for associated reef fishes and other biota. Secondary ecological effects, such as the concentration of predators on remnant surviving coral populations, have also accelerated the pace of decline in some areas. Although bleaching severity and recovery have been variable across all spatial scales, some reefs have experienced relatively rapid recovery from severe bleaching impacts. There has been a significant overall recovery of coral cover in the Indian Ocean, where many reefs were devastated by a single large bleaching event in 1998. In contrast, coral cover on western Atlantic reefs has generally continued to decline in response to multiple smaller bleaching events and a diverse set of chronic secondary stressors. No clear trends are apparent in the eastern Pacific, the central-southern-western Pacific or the Arabian Gulf, where some reefs are recovering and others are not. The majority of survivors and new recruits on regenerating and recovering coral reefs have originated from broadcast spawning taxa with a potential for asexual growth, relatively long distance dispersal, successful settlement, rapid growth and a capacity for framework construction. Whether or not affected reefs can continue to function as before will depend on: (1) how much coral cover is lost, and which species are locally extirpated; (2) the ability of remnant and recovering coral communities to adapt or acclimatize to higher temperatures and other climatic factors such as reductions in aragonite saturation state; (3) the changing balance between reef accumulation and bioerosion; and (4) our ability to maintain ecosystem resilience by restoring healthy levels of herbivory, macroalgal cover, and coral recruitment. Bleaching disturbances are likely to become a chronic stress in many reef areas in the coming decades, and coral communities, if they cannot recover quickly enough, are likely to be reduced to their most hardy or adaptable constituents. Some degraded reefs may already be approaching this ecological asymptote, although to date there have not been any global extinctions of individual coral species as a result of bleaching events. Since human populations inhabiting tropical coastal areas derive great value from coral reefs, the degradation of these ecosystems as a result of coral bleaching and its associated impacts is of considerable societal, as well as biological concern. Coral reef conservation strategies now recognize climate change as a principal threat, and are engaged in efforts to allocate conservation activity according to geographic-, taxonomic-, and habitat-specific priorities to maximize coral reef survival. Efforts to forecast and monitor bleaching, involving both remote sensed observations and coupled ocean–atmosphere climate models, are also underway. In addition to these efforts, attempts to minimize and mitigate bleaching impacts on reefs are immediately required. If significant reductions in greenhouse gas emissions can be achieved within the next two to three decades, maximizing coral survivorship during this time may be critical to ensuring healthy reefs can recover in the long term.” Andrew C. Baker, Peter W. Glynn, and Bernhard Riegl, Estuarine, Coastal and Shelf Science, Volume 80, Issue 4, 10 December 2008, Pages 435-471, doi:10.1016/j.ecss.2008.09.003. [full text]

Coral Reefs Under Rapid Climate Change and Ocean Acidification – Hoegh-Guldberg et al. (2007) “Atmospheric carbon dioxide concentration is expected to exceed 500 parts per million and global temperatures to rise by at least 2°C by 2050 to 2100, values that significantly exceed those of at least the past 420,000 years during which most extant marine organisms evolved. Under conditions expected in the 21st century, global warming and ocean acidification will compromise carbonate accretion, with corals becoming increasingly rare on reef systems. The result will be less diverse reef communities and carbonate reef structures that fail to be maintained. Climate change also exacerbates local stresses from declining water quality and overexploitation of key species, driving reefs increasingly toward the tipping point for functional collapse. This review presents future scenarios for coral reefs that predict increasingly serious consequences for reef-associated fisheries, tourism, coastal protection, and people. As the International Year of the Reef 2008 begins, scaled-up management intervention and decisive action on global emissions are required if the loss of coral-dominated ecosystems is to be avoided.” O. Hoegh-Guldberg, P. J. Mumby, A. J. Hooten, R. S. Steneck, P. Greenfield, E. Gomez, C. D. Harvell, P. F. Sale, A. J. Edwards, K. Caldeira, N. Knowlton, C. M. Eakin, R. Iglesias-Prieto, N. Muthiga, R. H. Bradbury, A. Dubi and M. E. Hatziolos, Science 14 December 2007: Vol. 318 no. 5857 pp. 1737-1742, DOI: 10.1126/science.1152509. [full text]

Effects of climate and seawater temperature variation on coral bleaching and mortality – McClanahan et al. (2007) “Coral bleaching due to thermal and environmental stress threatens coral reefs and possibly people who rely on their resources. Here we explore patterns of coral bleaching and mortality in East Africa in 1998 and 2005 in a region where the equatorial current and the island effect of Madagascar interact to create different thermal and physicochemical environments. A variety of temperature statistics were calculated, and their relationships with the degree-heating months (DHM), a good predictor of coral bleaching, determined. Changes in coral cover were analyzed from 29 sites that span >1000 km of coastline from Kenya to the Comoros Islands. Temperature patterns are influenced by the island effect, and there are three main temperature environments based on the rise in temperature over 52 years, measures of temperature variation, and DHM. Offshore sites north of Madagascar that included the Comoros had low temperature rises, low DHM, high standard deviations (SD), and the lowest relative coral mortality. Coastal sites in Kenya had moderate temperature rises, the lowest temperature SD, high DHM, and the highest relative coral mortality. Coastal sites in the south had the highest temperature rises, moderate SD and DHM, and low relative coral mortality. Consequently, the rate of temperature rise was less important than background variation, as reflected by SD and kurtosis measures of sea surface water temperature (SST), in predicting coral survival across 1998. Coral bleaching responses to a warm-water anomaly in 2005 were also negatively related to temperature variation, but positively correlated with the speed of water flow. Separating these effects is difficult; however, both factors will be associated with current environments on the opposite sides of reefs and islands. Reefs in current shadows may represent refugia where corals acclimate and adapt to environmental variation, which better prepares them for rising temperature and anomalies, even though these sites are likely to experience the fastest rates of temperature rise. We suggest that these sites are a conservation priority and should be targeted for management and further ecological research in order to understand acclimation, adaptation, and resilience to climate change.” McClanahan, Timothy R., Mebrahtu Ateweberhan, Christopher A. Muhando, Joseph Maina, and Mohammed S. Mohammed. 2007, Ecological Monographs 77:503–525, doi:10.1890/06-1182.1. [full text]

The role of zooxanthellae in the thermal tolerance of corals: a ‘nugget of hope’ for coral reefs in an era of climate change – Berkelmans & van Oppen (2006) “The ability of coral reefs to survive the projected increases in temperature due to global warming will depend largely on the ability of corals to adapt or acclimatize to increased temperature extremes over the next few decades. Many coral species are highly sensitive to temperature stress and the number of stress (bleaching) episodes has increased in recent decades. We investigated the acclimatization potential of Acropora millepora, a common and widespread Indo-Pacific hard coral species, through transplantation and experimental manipulation. We show that adult corals, at least in some circumstances, are capable of acquiring increased thermal tolerance and that the increased tolerance is a direct result of a change in the symbiont type dominating their tissues from Symbiodinium type C to D. Our data suggest that the change in symbiont type in our experiment was due to a shuffling of existing types already present in coral tissues, not through exogenous uptake from the environment. The level of increased tolerance gained by the corals changing their dominant symbiont type to D (the most thermally resistant type known) is around 1–1.5 °C. This is the first study to show that thermal acclimatization is causally related to symbiont type and provides new insight into the ecological advantage of corals harbouring mixed algal populations. While this increase is of huge ecological significance for many coral species, in the absence of other mechanisms of thermal acclimatization/adaptation, it may not be sufficient to survive climate change under predicted sea surface temperature scenarios over the next 100 years. However, it may be enough to ‘buy time’ while greenhouse reduction measures are put in place.” Ray Berkelmans and Madeleine J.H van Oppen, Proc. R. Soc. B 22 September 2006 vol. 273 no. 1599 2305-2312, doi: 10.1098/rspb.2006.3567. [full text]

Global assessment of coral bleaching and required rates of adaptation under climate change – Donner et al. (2005) “Elevated ocean temperatures can cause coral bleaching, the loss of colour from reef-building corals because of a breakdown of the symbiosis with the dinoflagellate Symbiodinium. Recent studies have warned that global climate change could increase the frequency of coral bleaching and threaten the long-term viability of coral reefs. These assertions are based on projecting the coarse output from atmosphere–ocean general circulation models (GCMs) to the local conditions around representative coral reefs. Here, we conduct the first comprehensive global assessment of coral bleaching under climate change by adapting the NOAA Coral Reef Watch bleaching prediction method to the output of a low- and high-climate sensitivity GCM. First, we develop and test algorithms for predicting mass coral bleaching with GCM-resolution sea surface temperatures for thousands of coral reefs, using a global coral reef map and 1985–2002 bleaching prediction data. We then use the algorithms to determine the frequency of coral bleaching and required thermal adaptation by corals and their endosymbionts under two different emissions scenarios. The results indicate that bleaching could become an annual or biannual event for the vast majority of the world’s coral reefs in the next 30–50 years without an increase in thermal tolerance of 0.2–1.0°C per decade. The geographic variability in required thermal adaptation found in each model and emissions scenario suggests that coral reefs in some regions, like Micronesia and western Polynesia, may be particularly vulnerable to climate change. Advances in modelling and monitoring will refine the forecast for individual reefs, but this assessment concludes that the global prognosis is unlikely to change without an accelerated effort to stabilize atmospheric greenhouse gas concentrations.” Simon D. Donner, William J. Skirving, Christopher M. Little, Michael Oppenheimer, Ove Hoegh-Guldberg, Global Change Biology, Volume 11, Issue 12, pages 2251–2265, December 2005. [full text]

Coral reefs: Corals’ adaptive response to climate change – Baker et al. (2004) “The long-term response of coral reefs to climate change depends on the ability of reef-building coral symbioses to adapt or acclimatize to warmer temperatures, but there has been no direct evidence that such a response can occur. Here we show that corals containing unusual algal symbionts that are thermally tolerant and commonly associated with high-temperature environments are much more abundant on reefs that have been severely affected by recent climate change. This adaptive shift in symbiont communities indicates that these devastated reefs could be more resistant to future thermal stress, resulting in significantly longer extinction times for surviving corals than had been previously assumed.” Andrew C. Baker, Craig J. Starger, Tim R. McClanahan & Peter W. Glynn, Nature 430, 741 (12 August 2004) | doi:10.1038/430741a. [full text]

Coral reef calcification and climate change: The effect of ocean warming – McNeil et al. (2004) “Coral reefs are constructed of calcium carbonate (CaCO3). Deposition of CaCO3 (calcification) by corals and other reef organisms is controlled by the saturation state of CaCO3 in seawater (Ω) and sea surface temperature (SST). Previous studies have neglected the effects of ocean warming in predicting future coral reef calcification rates. In this study we take into account both these effects by combining empirical relationships between coral calcification rate and Ω and SST with output from a climate model to predict changes in coral reef calcification rates. Our analysis suggests that annual average coral reef calcification rate will increase with future ocean warming and eventually exceed pre-industrial rates by about 35% by 2100. Our results suggest that present coral reef calcification rates are equivalent to levels in the late 19th century and does not support previous suggestions of large and potentially catastrophic decreases in the future.” McNeil, B. I., R. J. Matear, and D. J. Barnes (2004), Geophys. Res. Lett., 31, L22309, doi:10.1029/2004GL021541. [full text, comment by Kleypas et al., reply by McNeil et al.]

Global Trajectories of the Long-Term Decline of Coral Reef Ecosystems – Pandolfi et al. (2003) “Degradation of coral reef ecosystems began centuries ago, but there is no global summary of the magnitude of change. We compiled records, extending back thousands of years, of the status and trends of seven major guilds of carnivores, herbivores, and architectural species from 14 regions. Large animals declined before small animals and architectural species, and Atlantic reefs declined before reefs in the Red Sea and Australia, but the trajectories of decline were markedly similar worldwide. All reefs were substantially degraded long before outbreaks of coral disease and bleaching. Regardless of these new threats, reefs will not survive without immediate protection from human exploitation over large spatial scales.” John M. Pandolfi, Roger H. Bradbury, Enric Sala, Terence P. Hughes, Karen A. Bjorndal, Richard G. Cooke, Deborah McArdle, Loren McClenachan, Marah J. H. Newman, Gustavo Paredes, Robert R. Warner and Jeremy B. C. Jackson, Science 15 August 2003: Vol. 301 no. 5635 pp. 955-958, DOI: 10.1126/science.1085706.

Climate Change, Human Impacts, and the Resilience of Coral Reefs – Hughes et al. (2003) “The diversity, frequency, and scale of human impacts on coral reefs are increasing to the extent that reefs are threatened globally. Projected increases in carbon dioxide and temperature over the next 50 years exceed the conditions under which coral reefs have flourished over the past half-million years. However, reefs will change rather than disappear entirely, with some species already showing far greater tolerance to climate change and coral bleaching than others. International integration of management strategies that support reef resilience need to be vigorously implemented, and complemented by strong policy decisions to reduce the rate of global warming.” T. P. Hughes, A. H. Baird, D. R. Bellwood, M. Card, S. R. Connolly, C. Folke, R. Grosberg, O. Hoegh-Guldberg, J. B. C. Jackson, J. Kleypas, J. M. Lough, P. Marshall, M. Nyström, S. R. Palumbi, J. M. Pandolfi, B. Rosen and J. Roughgarden, Science 15 August 2003: Vol. 301 no. 5635 pp. 929-933, DOI: 10.1126/science.1085046. [full text]

Microbial diseases of corals and global warming – Rosenberg & Haim (2002) “Coral bleaching and other diseases of corals have increased dramatically during the last few decades. As outbreaks of these diseases are highly correlated with increased sea-water temperature, one of the consequences of global warming will probably be mass destruction of coral reefs. The causative agent(s) of a few of these diseases have been reported: bleaching of Oculina patagonica by Vibrio shiloi; black band disease by a microbial consortium; sea-fan disease (aspergillosis) by Aspergillus sydowii; and coral white plague possibly by Sphingomonas sp. In addition, we have recently discovered that Vibrio coralyticus is the aetiological agent for bleaching the coral Pocillopora damicornis in the Red Sea. In the case of coral bleaching by V. shiloi, the major effect of increasing temperature is the expression of virulence genes by the pathogen. At high summer sea-water temperatures, V. shiloi produces an adhesin that allows it to adhere to a β-galactoside-containing receptor in the coral mucus, penetrate into the coral epidermis, multiply intracellularly, differentiate into a viable-but-not-culturable (VBNC) state and produce toxins that inhibit photosynthesis and lyse the symbiotic zooxanthellae. In black band disease, sulphide is produced at the coral–microbial biofilm interface, which is probably responsible for tissue death. Reports of newly emerging coral diseases and the lack of epidemiological and biochemical information on the known diseases indicate that this will become a fertile area of research in the interface between microbial ecology and infectious disease.” Eugene Rosenberg, Yael Ben-Haim, Environmental Microbiology, Volume 4, Issue 6, pages 318–326, June 2002, DOI: 10.1046/j.1462-2920.2002.00302.x. [full text]

The future of coral reefs – Knowlton (2001) “Coral reefs, with their millions of species, have changed profoundly because of the effects of people, and will continue to do so for the foreseeable future. Reefs are subject to many of the same processes that affect other human-dominated ecosystems, but some special features merit emphasis: (i) Many dominant reef builders spawn eggs and sperm into the water column, where fertilization occurs. They are thus particularly vulnerable to Allee effects, including potential extinction associated with chronic reproductive failure. (ii) The corals likely to be most resistant to the effects of habitat degradation are small, short-lived “weedy” corals that have limited dispersal capabilities at the larval stage. Habitat degradation, together with habitat fragmentation, will therefore lead to the establishment of genetically isolated clusters of inbreeding corals. (iii) Increases in average sea temperatures by as little as 1°C, a likely result of global climate change, can cause coral “bleaching” (the breakdown of coral–algal symbiosis), changes in symbiont communities, and coral death. (iv) The activities of people near reefs increase both fishing pressure and nutrient inputs. In general, these processes favor more rapidly growing competitors, often fleshy seaweeds, and may also result in explosions of predator populations. (v) Combinations of stress appear to be associated with threshold responses and ecological surprises, including devastating pathogen outbreaks. (vi) The fossil record suggests that corals as a group are more likely to suffer extinctions than some of the groups that associate with them, whose habitat requirements may be less stringent.” Nancy Knowlton, PNAS May 8, 2001 vol. 98 no. 10 5419-5425, doi: 10.1073/pnas.091092998. [full text]

Coral bleaching: the winners and the losers – Loya et al. (2001) “Sea surface temperatures were warmer throughout 1998 at Sesoko Island, Japan, than in the 10 preceding years. Temperatures peaked at 2.8 °C above average, resulting in extensive coral bleaching and subsequent coral mortality. Using random quadrat surveys, we quantitatively documented the coral community structure one year before and one year after the bleaching event. The 1998 bleaching event reduced coral species richness by 61% and reduced coral cover by 85%. Colony morphology affected bleaching vulnerability and subsequent coral mortality. Finely branched corals were most susceptible, while massive and encrusting colonies survived. Most heavily impacted were the branched Acropora and pocilloporid corals, some of which showed local extinction. We suggest two hypotheses whose synergistic effect may partially explain observed mortality patterns (i.e. preferential survival of thick-tissued species, and shape-dependent differences in colony mass-transfer efficiency). A community-structural shift occurred on Okinawan reefs, resulting in an increase in the relative abundance of massive and encrusting coral species.” Loya, Sakai, Yamazato, Nakano, Sambali, Van Woesik, Ecology Letters, Volume 4, Issue 2, pages 122–131, March 2001, DOI: 10.1046/j.1461-0248.2001.00203.x.

Climate change, coral bleaching and the future of the world’s coral reefs – Hoegh-Guldberg (1999) “Sea temperatures in many tropical regions have increased by almost 1°C over the past 100 years, and are currently increasing at ~1–2°C per century. Coral bleaching occurs when the thermal tolerance of corals and their photosynthetic symbionts (zooxanthellae) is exceeded. Mass coral bleaching has occurred in association with episodes of elevated sea temperatures over the past 20 years and involves the loss of the zooxanthellae following chronic photoinhibition. Mass bleaching has resulted in significant losses of live coral in many parts of the world. This paper considers the biochemical, physiological and ecological perspectives of coral bleaching. It also uses the outputs of four runs from three models of global climate change which simulate changes in sea temperature and hence how the frequency and intensity of bleaching events will change over the next 100 years. The results suggest that the thermal tolerances of reef-building corals are likely to be exceeded every year within the next few decades. Events as severe as the 1998 event, the worst on record, are likely to become commonplace within 20 years. Most information suggests that the capacity for acclimation by corals has already been exceeded, and that adaptation will be too slow to avert a decline in the quality of the world’s reefs. The rapidity of the changes that are predicted indicates a major problem for tropical marine ecosystems and suggests that unrestrained warming cannot occur without the loss and degradation of coral reefs on a global scale.” Ove Hoegh-Guldberg, Marine and Freshwater Research 50(8) 839 – 866, doi:10.1071/MF99078. [full text]

The Significance of Emerging Diseases in the Tropical Coral Reef Ecosystem – Hayes & Goreau (1998) “Novel pathologies of coral reef organisms, especially reef frame building scleractinian corals, have escalated during the decade between 1987 and 1997. These emerging diseases have appeared with progressively greater frequency and over wider distribution, and have revealed more diversified characteristics than ever before. The causes of most of these infections are not yet confirmed, but they evidence a gradual decline in the vital status of the coral reef ecosystem. As specific causes are identified for these afflictions, terminology will shift from non-specific descriptions, such as “white band”, “white plague”, “white pox”, “yellow band” and “black band” diseases, to etiological and pathognomonic characterizations (e.g. aspergillosis and cyanobacteriosis). Stony corals are vulnerable to sedimentation, nutrient overloading, and chemical pollution from agricultural, urban, and domestic sources. They are incapable of relocation to other sites or of self-protection from cumulative effects of exposure to nitrates, phosphates, herbicides, pesticides, and raw sewage. In contrast to stresses attributed to warm water seasonal anomalies (e.g. coral reef bleaching), stresses imparted by pathogenic micro-organisms occur throughout the calendar year, fluctuate with changing temperature, and invariably result in tissue mortality. The coral has several mechanisms for defense. The epidermis, especially in tentacles of the coral polyp, contains nematocysts which are released in response to predators. The epidermal cells also possess cilia and a flagellary apparatus which are responsible for generating microcurrents in boundary water adjacent to the organism. These currents facilitate the entry of food into the coelenteron for digestion. Mesenterial filaments extend through the epidermis, sweep the surface of the colony, initiate digestion of food particles, and eventually return to the coelenteron. Both the epidermis and the gastrodermis contain mucocytes (or “immunocytes”) which release a mucous secretion. That mucous blanket physically insulates the tissue from particulates or soluble toxins, and may also be bacteriostatic because of immunoglobulin (IgA). The recent emergence of diseases in corals may be interpreted as the consequence of (1) changing coastal ocean water quality favoring the proliferation, attachment and colonization of microbes, and (2) reduced efficiency of the coral’s normal defenses. In order to appreciate these changes, research efforts to evaluate the microbial content of reef waters and to analyze the respective roles of mucus, cilia and flagella, and nematocysts of the corals are necessary. In this study, we have begun to detail the structural, physiological, chemical, and immunological attributes of the coral. Our analysis suggests that at least some of the emerging coral diseases may be explained by a decline in the capacity of coral colonies to mount effective protection against the increasing prevalence and varied invasive strategies of marine pathogens.” Raymond L. Hayes and Nora I. Goreau, Revista Biol Trop 46: 173–185. [full text is available in the abstract page]

Coral bleaching: causes and consequences – Brown (1997) “It has been over 10 years since the phenomenon of extensive coral bleaching was first described. In most cases bleaching has been attributed to elevated temperature, but other instances involving high solar irradiance, and sometimes disease, have also been documented. It is timely, in view of our concern about worldwide reef condition, to review knowledge of physical and biological factors involved in bleaching, the mechanisms of zooxanthellae and pigment loss, and the ecological consequences for coral communities. Here we evaluate recently acquired data on temperature and irradiance-induced bleaching, including long-term data sets which suggest that repeated bleaching events may be the consequence of a steadily rising background sea temperature that will in the future expose corals to an increasingly hostile environment. Cellular mechanisms of bleaching involve a variety of processes that include the degeneration of zooxanthellae in situ, release of zooxanthellae from mesenterial filaments and release of algae within host cells which become detached from the endoderm. Photo-protective defences (particularly carotenoid pigments) in zooxanthellae are likely to play an important role in limiting the bleaching response which is probably elicited by a combination of elevated temperature and irradiance in the field. The ability of corals to respond adaptively to recurrent bleaching episodes is not known, but preliminary evidence suggests that phenotypic responses of both corals and zooxanthellae may be significant.” B. E. Brown, Coral Reefs, Volume 16, Supplement 1, S129-S138, DOI: 10.1007/s003380050249. [full text]

Tracking South Pacific Coral Reef Bleaching
by Satellite and Field Observations – Goreau et al. (1997)
“South Pacific waters with anomalously high surface temperature were tracked by satellite to identify potential sites for field study of coral reef bleaching. Areas with warm season monthly anomalies exceeding +0.9 degrees C were verified to have coral bleaching by local observers, while other areas were not affected. Comparison of 15 environmental variables, measured at 19 field sites across the area affected in 1994, shows that bleaching correlates significantly only with anomalously high temperature. Live coral cover was inversely correlated with many human population density-dependent stresses, but these were not correlated to bleaching. Observations in the Indian and Atlantic Oceans also show that coral reefs worldwide are acclimated close to their upper temperature limits and probably unable to adapt rapidly to a +1 degree C anomalous warming during the warm season.” T. J. Goreau, R. L. Hayes, and A. E. Strong, Proceedings of the 8th International Coral Reef Symposium 2:1491-1494, 1997. [full text is available in the abstract page]

Coral bleaching relative to elevated seawater temperature in the Andaman Sea (Indian Ocean) over the last 50 years – Brown et al. (1996) Without abstract. B. E. Brown, R. P. Dunne and H. Chansang, Coral Reefs, Volume 15, Number 3, 151-152, DOI: 10.1007/BF01145885.

Periodic mass-bleaching and elevated sea temperatures: bleaching of outer reef slope communities in Moorea, French Polynesia – Hoegh-Guldberg & Salvat (1995) “Mass-bleaching events (in which corals and other symbiotic invertebrates lose their zooxanthellae) have been occurring every 3 to 4 yr since 1979. The last report of widespread mass-bleaching in the Pacific (which included bleaching around French Polynesia) was in February-April 1991. This paper reports on mass-bleaching along the outer reef slope of Moorea, French Polynesia, in April 1994. Mass-bleaching was extensive at all sites visited, with corals being bleached down to 25 m. Colour loss by corals was due to low areal densities of zooxanthellae and the percentage of live coral affected ranged between 39.6 (+/- 7.12, SEM) (NW sites) and 72.4 (+/- 7.11, SEM) (NE sites). Bleaching also varied as a function of depth and included a wide range of species. Acropora spp. showed the most severe bleaching (89.0 to 100% of all colonies completely bleached) and Porites spp. showed the least amount of bleaching (12.9 to 42.5% of all colonies partly bleached). Pocillopora spp. showed intermediate bleaching (73.9 to 92.1% of all colonies either partly or completely bleached). The results of this report indicate that current bleaching is on a scale equal to that of the 1991 bleaching event. Temperatures recorded hourly at 14 m off the outer reef slope from July 1991 to August 1994 (and those from satellite sea surface temperature readings) indicate unusually warm sea temperatures in March 1994, which were approximately 1.0*C higher than the highest temperatures recorded in 1992 and 1993, years in which bleaching on a massive scale did not occur. The appearance of warmer temperatures preceded the onset of bleaching by 2 to 3 wk, which strongly confirms the hypothesis that positive thermal anomalies are responsible for recent bleaching events in the Central and Western Pacific.” Hoegh-Guldberg O, Salvat B, MEPS 121:181-190 (1995), doi:10.3354/meps121181.

Catastrophes, Phase Shifts, and Large-Scale Degradation of a Caribbean Coral Reef – Hughes (1994) “Many coral reefs have been degraded over the past two to three decades through a combination of human and natural disturbances. In Jamaica, the effects of overfishing, hurricane damage, and disease have combined to destroy most corals, whose abundance has declined from more than 50 percent in the late 1970s to less than 5 percent today. A dramatic phase shift has occurred, producing a system dominated by fleshy macroalgae (more than 90 percent cover). Immediate implementation of management procedures is necessary to avoid further catastrophic damage.” Terence P. Hughes, Science 9 September 1994: Vol. 265 no. 5178 pp. 1547-1551, DOI: 10.1126/science.265.5178.1547. [full text]

1994 coral bleaching event, Society Islands, French Polynesia – Fagerstom & Rougerie (1994) “The progression of a temperature-induced bleaching event on the barrier reef at Passe d’Arue, Tahiti, during March–April 1994 was observed at approximately weekly intervals. The event consisted of selective exaggeration of polyp colours (Montipora verneuilli, Pocillopora verrucosa), fluorescence followed by bleaching (Acropora spp.), partial-complete bleaching (Fungia spp., Montastraea curta, anemones) and commencement of polyp death. Porites (massive spp.), P. (Synarea) rus and melobesoid algae were almost untouched by the event.” J.A. Fagerstrom and F. Rougerie, Marine Pollution Bulletin, Volume 29, Issues 1-3, 1994, Pages 34-35, doi:10.1016/0025-326X(94)90423-5. [full text]

Coral reef bleaching: ecological perspectives – Glynn (1993) “Coral reef bleaching, the whitening of diverse invertebrate taxa, results from the loss of symbiotic zooxanthellae and/or a reduction in photosynthetic pigment concentrations in zooxanthellae residing within the gastrodermal tissues of host animals. Of particular concern are the consequences of bleaching of large numbers of reef-building scleractinian corals and hydrocorals. Published records of coral reef bleaching events from 1870 to the present suggest that the frequency (60 major events from 1979 to 1990), scale (co-occurrence in many coral reef regions and often over the bathymetric depth range of corals) and severity (>95% mortality in some areas) of recent bleaching disturbances are unprecedented in the scientific literature. The causes of small scale, isolated bleaching events can often be explained by particular stressors (e.g., temperature, salinity, light, sedimentation, aerial exposure and pollutants), but attempts to explain large scale bleaching events in terms of possible global change (e.g., greenhouse warming, increased UV radiation flux, deteriorating ecosystem health, or some combination of the above) have not been convincing. Attempts to relate the severity and extent of large scale coral reef bleaching events to particular causes have been hampered by a lack of (a) standardized methods to assess bleaching and (b) continuous, long-term data bases of environmental conditions over the periods of interest. An effort must be made to understand the impact of bleaching on the remainder of the reef community and the long-term effects on competition, predation, symbioses, bioerosion and substrate condition, all factors that can influence coral recruitment and reef recovery. If projected rates of sea warming are realized by mid to late AD 2000, i.e. a 2°C increase in high latitude coral seas, the upper thermal tolerance limits of many reef-building corals could be exceeded. Present evidence suggests that many corals would be unable to adapt physiologically or genetically to such marked and rapid temperature increases.” P. W. Glynn, Coral Reefs, Volume 12, Number 1, 1-17, DOI: 10.1007/BF00303779.

Effects of disturbance on coral communities: bleaching in Moorea, French Polynesia – Gleason (1993) “This study examines patterns of susceptibility and short-term recovery of corals from bleaching. A mass coral bleaching event began in March, 1991 on reefs in Moorea, French Polynesia and affected corals on the shallow barrier reef and to >20 m depth on the outer forereef slope. There were significant differences in the effect of the bleaching among common coral genera, with Acropora, Montastrea, Montipora, and Pocillopora more affected than Porites, Pavona, leptastrea or Millepora. Individual colonies of the common species of Acropora and Pocillopora were marked and their fate assessed on a subsequent survey in August, 1991 to determine rates of recovery and mortality. Ninety-six percent of Acropora spp. showed some degree of bleaching compared to 76% of Pocillopora spp. From March to August mortality of bleached colonies of Pocillopora was 17%, 38% recovered completely, and many suffered some partial mortality of the tissue. In contrast, 63% of the Acropora spp. died, and about 10% recovered completely. Generally, those colonies with less than 50% of the colony area affected by the bleaching recovered at a higher rate than did those with more severe bleaching. Changes in community composition four months after the event began included a significant decrease only in crustose algae and an increase in cover of filamentous algae, much of which occupied plate-like and branching corals that had died in the bleaching event. Total coral cover and cover of susceptible coral genera had declined, but not significantly, after the event.” M. G. Gleason, Coral Reefs, Volume 12, Numbers 3-4, 193-201, DOI: 10.1007/BF00334479.

An Assessment of Global Warming Stress on Caribbean Coral Reef Ecosystems – Atwood et al. (1992) “There is evidence that stress on coral reef ecosystems in the Caribbean region is increasing. Recently numerous authors have stated that the major stress results from “abnormally high” seasonal sea surface temperatures (SST) and have implicated global warming as a cause, stating that recent episodes of coral bleaching result therefrom. However, an analysis of available SST data sets shows no discernible warming trend that could cause an increase in coral bleaching. Given the lack of long-term records synoptic with observations of coral ecosystem health, there is insufficient evidence available to label temperatures observed in coincidence with recent regional bleaching events as “abnormally” high.” Atwood, Donald K.; Hendee, James C.; Mendez, Antonio, Bulletin of Marine Science, Volume 51, Number 1, July 1992 , pp. 118-130(13).

Coral reef bleaching in the 1980s and possible connections with global warming – Glynn (1991) “Scleractinian corals and their symbiotic dinoflagellate algae build massive, wave-resistant coral reefs that are pre-eminent in shallow tropical seas. This mutualism is especially sensitive to numerous environmental stresses, and has been disrupted frequently during the past decade. Increased seawater temperatures have been proposed as the most likely cause of coral reef bleaching, and it has been suggested that the recent large-scale disturbances are the first biological indication of global warming. This article describes recent bleaching events and their possible link with sea warming and other environmental stresses, and offers some speculation on the fate of coral reefs if the Earth enters a sustained period of warming.” Peter W. Glynn, Trends in Ecology & Evolution, Volume 6, Issue 6, June 1991, Pages 175-179, doi:10.1016/0169-5347(91)90208-F.

Damage and recovery of coral reefs affected by El Niño related seawater warming in the Thousand Islands, Indonesia – Brown & Suharsono (1990) “Extensive coral bleaching occurred during sea-water warming (as a result of the 1982/3 El Niño Southern Oscillation event) in 1983 on the shallow reefs in the Java Sea. Mean seawater temperatures rose by 2–3° C over a six month period with values greater than 33° C being recorded between 1200–1500 h. As many as 80–90% of corals died on the reef flats at the study sites, with the major casualties being branching species in the genera Acropora and Pocillopora. Five years after the event the community structure of the study sites has recovered significantly, though coral cover is still 50% of its former level. Contrasting patterns of recovery at two selected sites, in close proximity to each other, are discussed.” B. E. Brown and Suharsono, Coral Reefs, Volume 8, Number 4, 163-170, DOI: 10.1007/BF00265007.

Widespread Coral Mortality and the 1982–83 El Niño Warming Event – Glynn (1984) “The massive ‘bleaching’ (loss of zooxanthellae) and death of reef corals that occurred in one area (Gulf of Chiriquí) on the Pacific side of Panamá and in the Galápagos Islands during February—April 1983 continued in these areas until September—October 1983, resulting in a catastrophic disturbance. Similar episodes have been reported subsequently throughout much of the tropical eastern Pacific region (Costa Rica, the entire Pacific coast of Panamá, and Colombia), in the central and western Pacific Ocean, in parts of the western Atlantic Ocean (Caribbean coasts of Costa Rica, Panamá, and Colombia), and in the Florida Keys and Bahama Islands.” Peter W. Glynn, Environmental Conservation (1984), 11: 133-146, DOI: 10.1017/S0376892900013825.

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Papers on CO2 fertilization effect

Posted by Ari Jokimäki on November 18, 2010

This is a list of papers on the CO2 fertilization effect to the plant growth. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Tree ring evidence for limited direct CO2 fertilization of forests over the 20th century – Gedalof & Berg (2010) “The effect that rising atmospheric CO2 levels will have on forest productivity and water use efficiency remains uncertain, yet it has critical implications for future rates of carbon sequestration and forest distributions. Efforts to understand the effect that rising CO2 will have on forests are largely based on growth chamber studies of seedlings, and the relatively small number of FACE sites. Inferences from these studies are limited by their generally short durations, artificial growing conditions, unnatural step-increases in CO2 concentrations, and poor replication. Here we analyze the global record of annual radial tree growth, derived from the International Tree ring Data Bank (ITRDB), for evidence of increasing growth rates that cannot be explained by climatic change alone, and for evidence of decreasing sensitivity to drought. We find that approximately 20 percent of sites globally exhibit increasing trends in growth that cannot be attributed to climatic causes, nitrogen deposition, elevation, or latitude, which we attribute to a direct CO2 fertilization effect. No differences were found between species in their likelihood to exhibit growth increases attributable to CO2 fertilization, although Douglas-fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa), the two most commonly sampled species in the ITRDB, exhibit a CO2 fertilization signal at frequencies very near their upper and lower confidence limits respectively. Overall these results suggest that CO2 fertilization of forests will not counteract emissions or slow warming in any substantial fashion, but do suggest that future forest dynamics may differ from those seen today depending on site conditions and individual species’ responses to elevated CO2.” Gedalof, Z., and A. A. Berg (2010), Global Biogeochem. Cycles, 24, GB3027, doi:10.1029/2009GB003699.

CO2 Enhancement of Forest Productivity Constrained by Limited Nitrogen Availability – Norby et al. (2009) “Here, we provide new evidence from a FACE experiment in a deciduous Liquidambar styraciflua (sweetgum) forest stand in Tennessee, USA, that N limitation has significantly reduced the stimulation of NPP by elevated atmospheric CO2 concentration (eCO2). Isotopic evidence and N budget analysis support the premise that N availability in this forest ecosystem has been declining over time, and declining faster in eCO2. Model analyses and evidence from leaf- and stand-level observations provide mechanistic evidence that declining N availability constrained the tree response to eCO2. These results provide a strong rationale and process understanding for incorporating N limitation and N feedback effects in ecosystem and global models used in climate change assessments.” Norby, Richard, Warren, Jeffrey, Iversen, Colleen, Garten, Charles, Medlyn, Belinda, and McMurtrie, Nature Precedings, hdl:10101/npre.2009.3747.1, 2009. [Full text]

Why is plant-growth response to elevated CO2 amplified when water is limiting, but reduced when nitrogen is limiting? A growth-optimisation hypothesis – McMurtrie et al. (2008) “Experimental evidence indicates that the stomatal conductance and nitrogen concentration ([N]) of foliage decline under CO2 enrichment, and that the percentage growth response to elevated CO2 is amplified under water limitation, but reduced under nitrogen limitation. We advance simple explanations for these responses based on an optimisation hypothesis applied to a simple model of the annual carbon–nitrogen–water economy of trees growing at a CO2-enrichment experiment at Oak Ridge, Tennessee, USA. The model is shown to have an optimum for leaf [N], stomatal conductance and leaf area index (LAI), where annual plant productivity is maximised. The optimisation is represented in terms of a trade-off between LAI and stomatal conductance, constrained by water supply, and between LAI and leaf [N], constrained by N supply. At elevated CO2 the optimum shifts to reduced stomatal conductance and leaf [N] and enhanced LAI. The model is applied to years with contrasting rainfall and N uptake. The predicted growth response to elevated CO2 is greatest in a dry, high-N year and is reduced in a wet, low-N year. The underlying physiological explanation for this contrast in the effects of water versus nitrogen limitation is that leaf photosynthesis is more sensitive to CO2 concentration ([CO2]) at lower stomatal conductance and is less sensitive to [CO2] at lower leaf [N].” Ross E. McMurtrie, Richard J. Norby, Belinda E. Medlyn, Roderick C. Dewar, David A. Pepper, Peter B. Reich, Craig V. M. Barton, Functional Plant Biology, 2008, 35(6) 521–534, doi:10.1071/FP08128. [Full text]

The Power of Monitoring Stations and a CO2 Fertilization Effect: Evidence from Causal Relationships between NDVI and Carbon Dioxide – Kaufmann et al. (2008) “Two hypotheses are tested: 1) monitoring stations (e.g., Mauna Loa) are not able to measure changes in atmospheric concentrations of CO2 that are generated by changes in terrestrial vegetation at distant locations; 2) changes in the atmospheric concentration of carbon dioxide do not affect terrestrial vegetation at large scales under conditions that now exist in situ, by estimating statistical models of the relationship between satellite measurements of the normalized difference vegetation index (NDVI) and the atmospheric concentration of carbon dioxide measured at Mauna Loa and Point Barrow. To go beyond simple correlations, the notion of Granger causality is used. Results indicate that the authors are able to identify locations where and months when disturbances to the terrestrial biota “Granger cause” atmospheric CO2. The authors are also able to identify locations where and months when disturbances to the atmospheric concentration of carbon dioxide generate changes in NDVI. Together, these results provide large-scale support for a CO2 fertilization effect and an independent empirical basis on which observations at monitoring stations can be used to test hypotheses and validate models regarding effect of the terrestrial biota on atmospheric concentrations of carbon dioxide.” Kaufmann, R. K., L. F. Paletta, H. Q. Tian, R. B. Myneni, R. D. D’Arrigo, 2008, Earth Interact., 12, 1–23, doi: 10.1175/2007EI240.1. [Full text]

Increases in nitrogen uptake rather than nitrogen-use efficiency support higher rates of temperate forest productivity under elevated CO2 – Finzi et al. (2007) “Forest ecosystems are important sinks for rising concentrations of atmospheric CO2. In previous research, we showed that net primary production (NPP) increased by 23 ± 2% when four experimental forests were grown under atmospheric concentrations of CO2 predicted for the latter half of this century. Because nitrogen (N) availability commonly limits forest productivity, some combination of increased N uptake from the soil and more efficient use of the N already assimilated by trees is necessary to sustain the high rates of forest NPP under free-air CO2 enrichment (FACE). In this study, experimental evidence demonstrates that the uptake of N increased under elevated CO2 at the Rhinelander, Duke, and Oak Ridge National Laboratory FACE sites, yet fertilization studies at the Duke and Oak Ridge National Laboratory FACE sites showed that tree growth and forest NPP were strongly limited by N availability. By contrast, nitrogen-use efficiency increased under elevated CO2 at the POP-EUROFACE site, where fertilization studies showed that N was not limiting to tree growth. Some combination of increasing fine root production, increased rates of soil organic matter decomposition, and increased allocation of carbon (C) to mycorrhizal fungi is likely to account for greater N uptake under elevated CO2. Regardless of the specific mechanism, this analysis shows that the larger quantities of C entering the below-ground system under elevated CO2 result in greater N uptake, even in N-limited ecosystems. Biogeochemical models must be reformulated to allow C transfers below ground that result in additional N uptake under elevated CO2.” Adrien C. Finzi, Richard J. Norby, Carlo Calfapietra, Anne Gallet-Budynek, Birgit Gielen, William E. Holmes, Marcel R. Hoosbeek, Colleen M. Iversen, Robert B. Jackson, Mark E. Kubiske, Joanne Ledford, Marion Liberloo, Ram Oren, Andrea Polle, Seth Pritchard, Donald R. Zak, William H. Schlesinger, and Reinhart Ceulemans, PNAS August 28, 2007 vol. 104 no. 35 14014-14019, doi: 10.1073/pnas.0706518104. [Full text]

Nitrogen limitation constrains sustainability of ecosystem response to CO2 – Reich et al. (2006) “Enhanced plant biomass accumulation in response to elevated atmospheric CO2 concentration could dampen the future rate of increase in CO2 levels and associated climate warming. However, it is unknown whether CO2-induced stimulation of plant growth and biomass accumulation will be sustained or whether limited nitrogen (N) availability constrains greater plant growth in a CO2-enriched world. Here we show, after a six-year field study of perennial grassland species grown under ambient and elevated levels of CO2 and N, that low availability of N progressively suppresses the positive response of plant biomass to elevated CO2. Initially, the stimulation of total plant biomass by elevated CO2 was no greater at enriched than at ambient N supply. After four to six years, however, elevated CO2 stimulated plant biomass much less under ambient than enriched N supply. This response was consistent with the temporally divergent effects of elevated CO2 on soil and plant N dynamics at differing levels of N supply. Our results indicate that variability in availability of soil N and deposition of atmospheric N are both likely to influence the response of plant biomass accumulation to elevated atmospheric CO2. Given that limitations to productivity resulting from the insufficient availability of N are widespread in both unmanaged and managed vegetation, soil N supply is probably an important constraint on global terrestrial responses to elevated CO2.” Peter B. Reich, Sarah E. Hobbie, Tali Lee, David S. Ellsworth, Jason B. West, David Tilman, Johannes M. H. Knops, Shahid Naeem and Jared Trost, Nature 440, 922-925 (13 April 2006) | doi:10.1038/nature04486.

Food for Thought: Lower-Than-Expected Crop Yield Stimulation with Rising CO2 Concentrations – Long et al. (2006) “Model projections suggest that although increased temperature and decreased soil moisture will act to reduce global crop yields by 2050, the direct fertilization effect of rising carbon dioxide concentration ([CO2]) will offset these losses. The CO2 fertilization factors used in models to project future yields were derived from enclosure studies conducted approximately 20 years ago. Free-air concentration enrichment (FACE) technology has now facilitated large-scale trials of the major grain crops at elevated [CO2] under fully open-air field conditions. In those trials, elevated [CO2] enhanced yield by ∼50% less than in enclosure studies. This casts serious doubt on projections that rising [CO2] will fully offset losses due to climate change.” Stephen P. Long, Elizabeth A. Ainsworth, Andrew D. B. Leakey, Josef Nösberger and Donald R. Ort, Science 30 June 2006, Vol. 312 no. 5782 pp. 1918-1921, DOI: 10.1126/science.1114722.

Effect of natural atmospheric CO2 fertilization suggested by open-grown white spruce in a dry environment – Wang et al. (2006) “Evidence of an atmospheric CO2-fertilization effect on radial growth rates was uncovered for open-grown white spruce in a mixed-grass prairie of southwestern Manitoba, Canada. Consistent upward trends of the residuals from dendroclimatic models indicated a decreased ability for climatic parameters to predict radial growth. Despite that a similar amount (61%) of the total variation in radial growth index was explained by climate for both young and old trees, residuals from young trees for the period of 1955–1999 demonstrated a stronger upward trend (R2=0.551, P<0.0001) than old trees for the period of 1900–1996 (R2=0.020, P=0.167). Similar to young trees, the residuals from the early growth period (1900–1929) of old trees also demonstrated a stronger upward trend (R2=0.480, P<0.0001) than the period of 1900–1996. Likewise, a comparable period (1970–1999) of young trees also demonstrated a stronger upward trend (R2=0.619, P<0.0001) than the early growth period (1900–1929) of old trees. In addition, postdrought growth response was much stronger for young trees (1970–1999) compared with old trees at the same development stage (1900–1929) (P=0.011) or within the same time period (1970–1999) (P=0.014). There was no difference (P=0.221) in drought recovery between the early (1900–1929) period and the late (1970–1999) period within old trees. Together, our results suggest that (1) open-grown white spruce trees improved their growth with time at the early developmental stage, and (2) at the same developmental stage, a greater growth response occurred in the late period when atmospheric CO2 concentration, and the rate of atmospheric CO2 increase were both relatively high. While it is impossible to rule out other factors, these results are consistent with expectations for CO2-fertilization effects.” G. Geoff Wang, Sophan Chhin, William L. Bauerle, Global Change Biology, Volume 12, Issue 3, pages 601–610, March 2006, DOI: 10.1111/j.1365-2486.2006.01098.x.

Forest response to elevated CO2 is conserved across a broad range of productivity – Norby et al. (2005) “Climate change predictions derived from coupled carbon-climate models are highly dependent on assumptions about feedbacks between the biosphere and atmosphere. One critical feedback occurs if C uptake by the biosphere increases in response to the fossil-fuel driven increase in atmospheric [CO2] (“CO2 fertilization”), thereby slowing the rate of increase in atmospheric [CO2]. Carbon exchanges between the terrestrial biosphere and atmosphere are often first represented in models as net primary productivity (NPP). However, the contribution of CO2 fertilization to the future global C cycle has been uncertain, especially in forest ecosystems that dominate global NPP, and models that include a feedback between terrestrial biosphere metabolism and atmospheric [CO2] are poorly constrained by experimental evidence. We analyzed the response of NPP to elevated CO2 (≈550 ppm) in four free-air CO2 enrichment experiments in forest stands. We show that the response of forest NPP to elevated [CO2] is highly conserved across a broad range of productivity, with a stimulation at the median of 23 ± 2%. At low leaf area indices, a large portion of the response was attributable to increased light absorption, but as leaf area indices increased, the response to elevated [CO2] was wholly caused by increased light-use efficiency. The surprising consistency of response across diverse sites provides a benchmark to evaluate predictions of ecosystem and global models and allows us now to focus on unresolved questions about carbon partitioning and retention, and spatial variation in NPP response caused by availability of other growth limiting resources.” Richard J. Norby, Evan H. DeLucia, Birgit Gielen, Carlo Calfapietra, Christian P. Giardina, John S. King, Joanne Ledford, Heather R. McCarthy, David J. P. Moore, Reinhart Ceulemans, Paolo De Angelis, Adrien C. Finzi, David F. Karnosky, Mark E. Kubiske, Martin Lukac, Kurt S. Pregitzer, Giuseppe E. Scarascia-Mugnozza, William H. Schlesinger, and Ram Oren, PNAS December 13, 2005 vol. 102 no. 50 18052-18056, doi: 10.1073/pnas.0509478102. [Full text]

Climate change impacts on crop yield and quality with CO2 fertilization in China – Erda et al. (2005) “A regional climate change model (PRECIS) for China, developed by the UK’s Hadley Centre, was used to simulate China’s climate and to develop climate change scenarios for the country. Results from this project suggest that, depending on the level of future emissions, the average annual temperature increase in China by the end of the twenty-first century may be between 3 and 4 °C. Regional crop models were driven by PRECIS output to predict changes in yields of key Chinese food crops: rice, maize and wheat. Modelling suggests that climate change without carbon dioxide (CO2) fertilization could reduce the rice, maize and wheat yields by up to 37% in the next 20–80 years. Interactions of CO2 with limiting factors, especially water and nitrogen, are increasingly well understood and capable of strongly modulating observed growth responses in crops. More complete reporting of free-air carbon enrichment experiments than was possible in the Intergovernmental Panel on Climate Change’s Third Assessment Report confirms that CO2 enrichment under field conditions consistently increases biomass and yields in the range of 5–15%, with CO2 concentration elevated to 550 ppm Levels of CO2 that are elevated to more than 450 ppm will probably cause some deleterious effects in grain quality. It seems likely that the extent of the CO2 fertilization effect will depend upon other factors such as optimum breeding, irrigation and nutrient applications.” Lin Erda, Xiong Wei, Ju Hui, Xu Yinlong, Li Yue, Bai Liping and Xie Liyong, Phil. Trans. R. Soc. B 29 November 2005 vol. 360 no. 1463 2149-2154, doi: 10.1098/rstb.2005.1743. [Full text]

Fine-root production dominates response of a deciduous forest to atmospheric CO2 enrichment – Norby et al. (2004) “Fine-root production and turnover are important regulators of the biogeochemical cycles of ecosystems and key components of their response to global change. We present a nearly continuous 6-year record of fine-root production and mortality from minirhizotron analysis of a closed-canopy, deciduous sweetgum forest in a free-air CO2 enrichment experiment. Annual production of fine roots was more than doubled in plots with 550 ppm CO2 compared with plots in ambient air. This response was the primary component of the sustained 22% increase in net primary productivity. Annual fine-root mortality matched annual production, and the mean residence time of roots was not altered by elevated CO2, but peak fine-root standing crop in midsummer was significantly higher in CO2-enriched plots, especially deeper in the soil profile. The preferential allocation of additional carbon to fine roots, which have a fast turnover rate in this species, rather than to stemwood reduces the possibility of long-term enhancement by elevated CO2 of carbon sequestration in biomass. However, sequestration of some of the fine-root carbon in soil pools is not precluded, and there may be other benefits to the tree from a seasonally larger and deeper fine-root system. Root-system dynamics can explain differences among ecosystems in their response to elevated atmospheric CO2; hence, accurate assessments of carbon flux and storage in forests in a globally changing atmosphere must account for this unseen and difficult-to-measure component.” Richard J. Norby, Joanne Ledford, Carolyn D. Reilly, Nicole E. Miller, and Elizabeth G. O’Neill, PNAS June 29, 2004 vol. 101 no. 26 9689-9693, doi: 10.1073/pnas.0403491101. [Full text]

Net primary productivity of a CO2-enriched deciduous forest and the implications for carbon storage – Norby et al. (2002) “A central question concerning the response of terrestrial ecosystems to a changing atmosphere is whether increased uptake of carbon in response to increasing atmospheric carbon dioxide concentration results in greater plant biomass and carbon storage or, alternatively, faster cycling of C through the ecosystem. Net primary productivity (NPP) of a closed-canopy Liquidambar styraciflua (sweetgum) forest stand was assessed for three years in a free-air CO2-enrichment (FACE) experiment. NPP increased 21% in stands exposed to elevated CO2, and there was no loss of response over time. Wood increment increased significantly during the first year of exposure, but subsequently most of the extra C was allocated to production of leaves and fine roots. These pools turn over more rapidly than wood, thereby reducing the potential of the forest stand to sequester additional C in response to atmospheric CO2 enrichment. Hence, while this experiment provides the first evidence that CO2 enrichment can increase productivity in a closed-canopy deciduous forest, the implications of this result must be tempered because the increase in productivity resulted in faster cycling of C through the system rather than increased C storage in wood. The fate of the additional C entering the soil system and the environmental interactions that influence allocation need further investigation.” Richard J. Norby, Paul J. Hanson, Elizabeth G. O’Neill, Tim J. Tschaplinski, Jake F. Weltzin, Randi A. Hansen, Weixin Cheng, Stan D. Wullschleger, Carla A. Gunderson, Nelson T. Edwards, and Dale W. Johnson, 2002, Ecological Applications 12:1261–1266, doi:10.1890/1051-0761(2002)012[1261:NPPOAC]2.0.CO;2. [Full text]

Soil fertility limits carbon sequestration by forest ecosystems in a CO2-enriched atmosphere – Oren et al. (2001) “Northern mid-latitude forests are a large terrestrial carbon sink. Ignoring nutrient limitations, large increases in carbon sequestration from carbon dioxide (CO2) fertilization are expected in these forests. Yet, forests are usually relegated to sites of moderate to poor fertility, where tree growth is often limited by nutrient supply, in particular nitrogen. Here we present evidence that estimates of increases in carbon sequestration of forests, which is expected to partially compensate for increasing CO2 in the atmosphere, are unduly optimistic. In two forest experiments on maturing pines exposed to elevated atmospheric CO2, the CO2-induced biomass carbon increment without added nutrients was undetectable at a nutritionally poor site, and the stimulation at a nutritionally moderate site was transient, stabilizing at a marginal gain after three years. However, a large synergistic gain from higher CO2 and nutrients was detected with nutrients added. This gain was even larger at the poor site (threefold higher than the expected additive effect) than at the moderate site (twofold higher). Thus, fertility can restrain the response of wood carbon sequestration to increased atmospheric CO2. Assessment of future carbon sequestration should consider the limitations imposed by soil fertility, as well as interactions with nitrogen deposition.” Ram Oren, David S. Ellsworth, Kurt H. Johnsen, Nathan Phillips, Brent E. Ewers, Chris Maier, Karina V.R. Schäfer, Heather McCarthy, George Hendrey, Steven G. McNulty & Gabriel G. Katul, Nature 411, 469-472 (24 May 2001) | doi:10.1038/35078064. [Full text]

Transient nature of CO2 fertilization in Arctic tundra – Oechel et al. (1994) “THERE has been much debate about the effect of increased atmospheric CO2 concentrations on plant net primary production and on net ecosystem CO2 flux. Apparently conflicting experimental findings could be the result of differences in genetic potential and resource availability, different experimental conditions and the fact that many studies have focused on individual components of the system rather than the whole ecosystem. Here we present results of an in situ experiment on the response of an intact native ecosystem to elevated CO2. An undisturbed patch of tussock tundra at Toolik Lake, Alaska, was enclosed in greenhouses in which the CO2 level, moisture and temperature could be controlled, and was subjected to ambient (340 p.p.m.) and elevated (680 p.p.m.) levels of CO2 and temperature (+4 °C). Air humidity, precipitation and soil water table were maintained at ambient control levels. For a doubled CO2 level alone, complete homeostasis of the CO2 flux was re-established within three years, whereas the regions exposed to a combination of higher temperatures and doubled CO2 showed persistent fertilization effect on net ecosystem carbon sequestration over this time. This difference may be due to enhanced sink activity from the direct effects of higher temperatures on growth and to indirect effects from enhanced nutrient supply caused by increased mineralization. These results indicate that the responses of native ecosystems to elevated CO2 may not always be positive, and are unlikely to be straightforward. Clearly, CO2 fertilization effects must always be considered in the context of genetic limitation, resource availability and other such factors.” Walter C. Oechel, Sid Cowles, Nancy Grulke, Steven J. Hastings, Bill Lawrence, Tom Prudhomme, George Riechers, Boyd Strain, David Tissue & George Vourlitis, Nature 371, 500 – 503 (06 October 1994); doi:10.1038/371500a0.

Tree growth in carbon dioxide enriched air and its implications for global carbon cycling and maximum levels of atmospheric CO2 – Idso & Kimball (1993) “In the longest carbon dioxide enrichment experiment ever conducted, well-watered and adequately fertilized sour orange tree seedlings were planted directly into the ground at Phoenix, Arizona, in July 1987 and continuously exposed, from mid-November of that year, to either ambient air or air enriched with an extra 300 ppmv of CO2 in clear-plastic-wall open-top enclosures. Only 18 months later, the CO2-enriched trees had grown 2.8 times larger than the ambient-treated trees; and they have maintained that productivity differential to the present day. This tremendous growth advantage is due to two major factors: a CO2-induced increase in daytime net photosynthesis and a CO2-induced reduction in nighttime dark respiration. Measurements of these physiological processes in another experiment have shown three Australlian tree species to respond similarly; while an independent study of the atmosphere’s seasonal CO2 cycle suggests that all earth’s trees, in the mean, probably share this same response. A brief review of the plant science literature outlines how such a large growth response to atmospheric CO2 enrichment might possibly be maintained in light of resource limitations existing in nature. Finally, it is noted that a CO2 “fertilization effect” of this magnitude should substantially slow the rate at which anthropogenic carbon dioxide would otherwise accumulate in the atmosphere, possibly putting an acceptable upper limit on the level to which the CO2 content of the air may ultimately rise.” Idso, S. B., and B. A. Kimball (1993), Global Biogeochem. Cycles, 7(3), 537–555, doi:10.1029/93GB01164.

Posted in Global warming effects | 3 Comments »

Papers on media and climate change

Posted by Ari Jokimäki on October 4, 2010

This is a list of papers on the media and climate change. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (February 2, 2011): “Additional papers” section added including lot of papers. Thanks to Alon for providing a huge list of papers, see the comment section.

Self-censorship and science: a geographical review of media coverage of climate tipping points – Antilla (2010) “Public perception of global climate change is strongly influenced by media constructions of scientific knowledge. This paper explores recent scientific findings and the press coverage thereof and is based on a content analysis of two years of global reporting on climate related positive feedback mechanisms (climate system responses to global warming which lead to further warming). Results indicate that non-US news organizations, especially in the UK, are at the forefront of the discourse on climate feedback loops. Poor US press coverage on such climate thresholds might be understood not only as self-censorship, but as a “false negative” error.” Liisa Antilla, Public Understanding of Science March 2010 vol. 19 no. 2 240-256, doi: 10.1177/0963662508094099. [Full text]

Media, Politics and Climate Change: Towards a New Research Agenda – Anderson (2009) “Climate change is one of the most pressing issues of our time, and the media have been demonstrated to play a key role in shaping public perceptions and policy agendas. Journalists are faced with multiple challenges in covering this complex field. This article provides an overview of existing research on the media framing of climate change, highlighting major research themes and assessing future potential research developments. It argues that analysis of the reporting of climate science must be placed in the wider context of the growing concentration and globalization of news media ownership, and an increasingly ‘promotional culture’, highlighted by the rapid rise of the public relations industry in recent years and claims-makers who employ increasingly sophisticated media strategies. Future research will need to examine in-depth the targeting of media by a range of actors, as well as unravel complex information flows across countries as media increasingly converge.” [Full text]

Global warming—global responsibility? Media frames of collective action and scientific certainty – Olausson (2009) “The increasing interconnectedness of the world that characterizes the process of globalization compels us to interlink local, national, and transnational phenomena, such as environmental risks, in both journalistic and academic discourse. Among environmental risks of global scope climate change is probably the one receiving the most attention at present, not least in the media. Globalization notwithstanding, national media are still dominated by a national logic in the presentation of news, and tensions arise between this media logic and the transnational character of environmental risks that call for a collective responsibility transcending the borders of the nation-states. This article presents results from studies of the construction of global climate change in three Swedish newspapers. It discusses the media’s attribution of responsibility for collective action along an axis ranging from local to national to transnational, and highlights the media’s reluctance to display any kind of scientific uncertainty that would undermine the demand for collective action. The results underline the media’s responsiveness to the political setting in which they operate and the growing relevance of the transnational political realm of Europe for the construction of news frames on global climate change in European national media.” [Full text]

Ideological cultures and media discourses on scientific knowledge: re-reading news on climate change – Carvalho (2007) “Focusing on the representation of climate change in the British “quality press,” this article argues that the discursive (re)construction of scientific claims in the media is strongly entangled with ideological standpoints. Understood here as a set of ideas and values that legitimate a program of action vis-à-vis a given social and political order, ideology works as a powerful selection device in deciding what is scientific news, i.e. what the relevant “facts” are, and who are the authorized “agents of definition” of science matters. The representation of scientific knowledge has important implications for evaluating political programs and assessing the responsibility of both governments and the public in addressing climate change.” Anabela Carvalho, Public Understanding of Science April 2007 vol. 16 no. 2 223-243, doi: 10.1177/0963662506066775. [Full text]

Flogging a dead norm? Newspaper coverage of anthropogenic climate change in the United States and United Kingdom from 2003 to 2006 – Boykoff (2007) “The journalistic norm of ‘balanced’ reporting (giving roughly equal coverage to both sides in any significant dispute) is recognised as both useful and problematic in communicating emerging scientific consensus on human attribution for global climate change. Analysis of the practice of this norm in United States (US) and United Kingdom (UK) newspaper coverage of climate science between 2003 and 2006 shows a significant divergence from scientific consensus in the US in 2003–4, followed by a decline in 2005–6, but no major divergence in UK reporting. These findings inform ongoing considerations about the spatially-differentiated media terms and conditions through which current and future climate policy is negotiated and implemented.” [Full text]

From convergence to contention: United States mass media representations of anthropogenic climate change science – Boykoff (2007) “This article focuses on connected factors that contribute to United States (US) media reporting on anthropogenic climate change science. It analyses US newspapers and television news from 1995 to 2006 as well as semi-structured interviews with climate scientists and environmental journalists. Through analyses of power and scale, the paper brings together issues of framing in journalism to questions of certainty/uncertainty in climate science. The paper examines how and why US media have represented conflict and contentions, despite an emergent consensus view regarding anthropogenic climate science.” Maxwell T Boykoff, Transactions of the Institute of British Geographers, Volume 32, Issue 4, pages 477–489, October 2007, DOI: 10.1111/j.1475-5661.2007.00270.x. [Full text]

A Tale of Two Fears: Exploring Media Depictions of Nuclear Power and Global Warming – Palfreman (2006) “Advanced technologies like nuclear power and looming environmental threats such as global climate change present major policy challenge for modern cultures. Public policy about such crucial and complex issues depends on public attitudes, which, in turn, tend to be strongly affected by mass media coverage. How “well” has the mass media portrayed these two evolving risk stories? Employing perspectives from both journalism and social science, this article will first review the history of mass media coverage of each topic, then analyze their differences.” Jon Palfreman, Review of Policy Research, Volume 23, Issue 1, pages 23–43, January 2006, DOI: 10.1111/j.1541-1338.2006.00184.x.

Climate of scepticism: US newspaper coverage of the science of climate change – Antilla (2005) “This two-part study integrates a quantitative review of one year of US newspaper coverage of climate science with a qualitative, comparative analysis of media-created themes and frames using a social constructivist approach. In addition to an examination of newspaper articles, this paper includes a reflexive comparison with attendant wire stories and scientific texts. Special attention is given to articles constructed with and framed by rhetoric emphasising uncertainty, controversy, and climate scepticism.” Liisa Antilla, Global Environmental Change Part A, Volume 15, Issue 4, December 2005, Pages 338-352, doi:10.1016/j.gloenvcha.2005.08.003. [Full text]

Cultural Circuits of Climate Change in U.K. Broadsheet Newspapers, 1985-2003 – Carvalho & Burgess (2005) “This article argues for a cultural perspective to be brought to bear on studies of climate change risk perception. Developing the “circuit of culture” model, the article maintains that the producers and consumers of media texts are jointly engaged in dynamic, meaning-making activities that are context-specific and that change over time. A critical discourse analysis of climate change based on a database of newspaper reports from three U.K. broadsheet papers over the period 1985-2003 is presented. This empirical study identifies three distinct circuits of climate change—1985-1990, 1991-1996, 1997-2003—which are characterized by different framings of risks associated with climate change. The article concludes that there is evidence of social learning as actors build on their experiences in relation to climate change science and policy making. Two important factors in shaping the U.K.’s broadsheet newspapers’ discourse on “dangerous” climate change emerge as the agency of top political figures and the dominant ideological standpoints in different newspapers.” Carvalho, Anabela; Burgess, Jacquelin, Risk Analysis, Volume 25, Number 6, December 2005 , pp. 1457-1469(13), DOI: 10.1111/j.1539-6924.2005.00692.x. [Full text]

Balance as bias: global warming and the US prestige press – Boykoff & Boykoff (2004) “This paper demonstrates that US prestige-press coverage of global warming from 1988 to 2002 has contributed to a significant divergence of popular discourse from scientific discourse. This failed discursive translation results from an accumulation of tactical media responses and practices guided by widely accepted journalistic norms. Through content analysis of US prestige press—meaning the New York Times, the Washington Post, the Los Angeles Times, and the Wall Street Journal—this paper focuses on the norm of balanced reporting, and shows that the prestige press’s adherence to balance actually leads to biased coverage of both anthropogenic contributions to global warming and resultant action.” Maxwell T. Boykoff and Jules M. Boykoff, Global Environmental Change Part A, Volume 14, Issue 2, July 2004, Pages 125-136, doi:10.1016/j.gloenvcha.2003.10.001. [Full text]

Testing Public (Un)Certainty of Science Media Representations of Global Warming – Corbett & Dufree (2004) “This exploratory study examines whether readers’assessments of the certainty of scientific findings depend on characteristics of news stories. An experimental design tested whether adding controversy and/or context to a news story about global warming influenced readers’ perceptions of its certainty. Respondents (N = 209) were randomly assigned to read one treatment and answer a questionnaire. Overall, there was a significant difference in readers’assessment of the certainty of global warming across treatments (F = 12.59, p = .00). The context treatment produced the highest level of certainty about global warming and differed significantly from the control treatment (with neither context nor controversy) and from the controversy treatment. Control and controversy treatments resulted in the lowest levels of certainty. There was an interaction effect between treatment and environmental ideology upon certainty (F = 1.64, p = .03) and a correlation between environmental ideology and prior certainty about global warming (r = .35, p = .01), suggesting that those with proenvironmental ideology were less swayed by the treatments.” Julia B. Corbett and Jessica L. Durfee, Science Communication December 2004 vol. 26 no. 2 129-151, doi: 10.1177/1075547004270234. [Full text]

Media’s social construction of environmental issues: focus on global warming – a comparative study – Dispensa & Brulle (2003) “Global warming has been a well recognized environmental issue in the United States for the past ten years, even though scientists had identified it as a potential problem years before in 1896. We find debate about the issue in the United States media coverage while controversy among the majority of scientists is rare. The role that media plays in constructing the norms and ideas in society is researched to understand how they socially construct global warming and other environmental issues. To identify if the U.S. Media presents a biased view of global warming, the following are discussed (1) the theoretical perspective of media and the environment; (2) scientific overview and history of global warming; (3) media coverage of global warming, and (4) research findings from the content analysis of three countries’ newspaper articles and two international scientific journals produced in 2000 with comparison of these countries economies, industries, and environments. In conclusion, our research demonstrates that the U.S. with differing industries, predominantly dominated by the fossil fuel industry, in comparison to New Zealand and Finland has a significant impact on the media coverage of global warming. The U.S’s media states that global warming is controversial and theoretical, yet the other two countries portray the story that is commonly found in the international scientific journals. Therefore, media, acting as one driving force, is providing citizens with piecemeal information that is necessary to assess the social, environmental and political conditions of the country and world.” Jaclyn Marisa Dispensa, Robert J. Brulle, 2003, International Journal of Sociology and Social Policy, Vol. 23 Iss: 10, pp.74 – 105. [Full text]

How Science Contributes to Environmental Reporting in British Newspapers: A Case Study of the Reporting of Global Warming and Climate Change – Taylor & Nathan (2002) “This article examines the role of science in environmental reporting in a number of British newspapers. The findings indicated that in reporting about global warming and climate change, the views of scientists were used to give legitimacy to the content of articles. However, in both the tabloids and broadsheets, there was little evidence provided, in the form of data, to substantiate the claims being made. Furthermore, uncertainties about global warming were not explored effectively. Newspaper reports tended to focus on the potential consequences of global warming, but made little attempt to address the suspected causes that would inevitably involve criticism of highly consumptive lifestyles in the west.” Neil Taylor and Subhashni Nathan, The Environmentalist, Volume 22, Number 4, 325-331, DOI: 10.1023/A:1020762813548.

Heat and hot air: influence of local temperature on journalists’ coverage of global warming – Shanahan & Good (2000) “This study examines relationships between local temperature in two cities (New York and Washington, D.C.) and coverage of global climate change in their local newspapers (the Times and the Post). The results show that there are some relationships between local temperature and frequency of attention to climate issues, such that journalists are more likely to discuss climate during unusually warm periods. However, support for the hypotheses was only partial; the Post did not show confirming relationships. The discussion focuses on implications for public understanding of climate change.” James Shanahan, Jennifer Good, Public Understanding of Science July 2000 vol. 9 no. 3 285-295, doi: 10.1088/0963-6625/9/3/305.

Telling Stories About Global Climate Change – McComas & Shanahan (1999) “A theory of cyclical patterns in media coverage of environmental issues must account for more than intrinsic qualities of the issues themselves: Narrative factors must be considered. A content analysis of The New York Times and The Washington Post stories from 1980 to 1995 shows how media construct narratives about global warming and how these narratives may influence attention cycles. Empirically, the frequency of newspaper coverage shows cyclical attention to global warming. The content analysis further reveals that implied danger and consequences of global warming gain more prominence on the upswing of newspaper attention, whereas controversy among scientists receives greater attention in the maintenance phase. The economics of dealing with global warming also receive greater attention during the maintenance and downside of the attention cycle. The discussion offers a narrative explanation and suggests the outcome of the “master story” of global climate change may discourage future attention to global warming.” Katherine McComas, James Shanahan, Communication Research February 1999 vol. 26 no. 1 30-57, doi: 10.1177/009365099026001003.

Global Environmental Change in the News: 1987-90 vs 1992-6 – Mazur (1998) “Hazards to the global environment, including climate change, ozone depletion, rainforest destruction, & species extinction, became important problems on the US agenda of risks after extensive media coverage, 1987-1990, & were subsequently taken up by other nations, at least until news coverage fell after 199O. Shown here is why these particular hazards, which had all been recognized by experts for years, suddenly became important news stories, & why they failed to attract much media attention during the period 1992-1996, a time when global warming & other problems intensified, & the White House was occupied by an administration ostensibly sympathetic to environmental concerns.” Mazur, A., International Sociology. Vol. 13, no. 4, pp. 457-472. 1998.

Additional papers

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Wilkins, L. (1993). Between facts and values: print media coverage of the greenhouse effect, 1987-1990. Public Understanding of Science, 2(1), 71 -84. doi:10.1088/0963-6625/2/1/005

Wilkins, L., & Patterson, P. (1991). Science as symbol: the media chills the greenhouse effect. In L. Wilkins & P. Patterson (Eds.), Risky business: Communicating issues of science, risk, and public policy (pp. 159–76). New York: Greenwood.

Wilson, K. M. (1995). Mass media as sources of global warming knowledge. Mass Comm Review, 22, 75-89.

Wilson, K. M. (2000a). Communicating climate change through the media. In S. Allan, B. Adam, & C. Carter (Eds.), Environmental risks and the media (pp. 201-217). London: Routledge.

Wilson, K. M. (2000b). Drought, debate, and uncertainty: measuring reporters’ knowledge and ignorance about climate change. Public Understanding of Science, 9(1), 1 -13. doi:10.1088/0963-6625/9/1/301

Wilson, K. M. (2002). Forecasting the Future. Science Communication, 24(2), 246 -268. doi:10.1177/107554702237849

Woods, R., Fernandez, A., & Coen, S.The use of religious metaphors by UK newspapers to describe and denigrate climate change. Public Understanding of Science. doi:10.1177/0963662510385061

Worthy, K. (2008). Modern Institutions, Phenomenal Dissociations, and Destructiveness Toward Humans and the Environment. Organization & Environment, 21(2), 148 -170. doi:10.1177/1086026608318987

Zehr, S. C. (2000). Public representations of scientific uncertainty about global climate change. Public Understanding of Science, 9(2), 85-103. doi:10.1088/0963-6625/9/2/301

Zhao, X. (2009). Media Use and Global Warming Perceptions. Communication Research, 36(5), 698 -723. doi:10.1177/0093650209338911

Zia, A., & Todd, A. M. (2010). Evaluating the effects of ideology on public understanding of climate change science: How to improve communication across ideological divides? Public Understanding of Science, 19(6), 743 -761. doi:10.1177/0963662509357871

Posted in Climate claims, Global warming effects | 6 Comments »

Papers on primary production and climate change

Posted by Ari Jokimäki on August 20, 2010

This is a list of papers on terrestrial net primary production and climate change. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Drought-Induced Reduction in Global Terrestrial Net Primary Production from 2000 Through 2009 – Zhao & Running (2010) “Terrestrial net primary production (NPP) quantifies the amount of atmospheric carbon fixed by plants and accumulated as biomass. Previous studies have shown that climate constraints were relaxing with increasing temperature and solar radiation, allowing an upward trend in NPP from 1982 through 1999. The past decade (2000 to 2009) has been the warmest since instrumental measurements began, which could imply continued increases in NPP; however, our estimates suggest a reduction in the global NPP of 0.55 petagrams of carbon. Large-scale droughts have reduced regional NPP, and a drying trend in the Southern Hemisphere has decreased NPP in that area, counteracting the increased NPP over the Northern Hemisphere. A continued decline in NPP would not only weaken the terrestrial carbon sink, but it would also intensify future competition between food demand and proposed biofuel production.” Science 20 August 2010: Vol. 329. no. 5994, pp. 940 – 943, DOI: 10.1126/science.1192666.

Global potential net primary production predicted from vegetation class, precipitation, and temperature – Del Grosso et al. (2008) “Net primary production (NPP), the difference between CO2 fixed by photosynthesis and CO2 lost to autotrophic respiration, is one of the most important components of the carbon cycle. Our goal was to develop a simple regression model to estimate global NPP using climate and land cover data. Approximately 5600 global data points with observed mean annual NPP, land cover class, precipitation, and temperature were compiled. Precipitation was better correlated with NPP than temperature, and it explained much more of the variability in mean annual NPP for grass- or shrub-dominated systems (r2 = 0.68) than for tree-dominated systems (r2 = 0.39). For a given precipitation level, tree-dominated systems had significantly higher NPP (~100–150 g C·m-2·yr-1) than non-tree-dominated systems. Consequently, previous empirical models developed to predict NPP based on precipitation and temperature (e.g., the Miami model) tended to overestimate NPP for non-tree-dominated systems. Our new model developed at the National Center for Ecological Analysis and Synthesis (the NCEAS model) predicts NPP for tree-dominated systems based on precipitation and temperature; but for non-tree-dominated systems NPP is solely a function of precipitation because including a temperature function increased model error for these systems. Lower NPP in non-tree-dominated systems is likely related to decreased water and nutrient use efficiency and higher nutrient loss rates from more frequent fire disturbances. Late 20th century aboveground and total NPP for global potential native vegetation using the NCEAS model are estimated to be ~28 Pg and ~46 Pg C/yr, respectively. The NCEAS model estimated an ~13% increase in global total NPP for potential vegetation from 1901 to 2000 based on changing precipitation and temperature patterns.” Ecology, 89:2117—2126, doi:10.1890/07-0850.1. [Full text]

Europe-wide reduction in primary productivity caused by the heat and drought in 2003 – Ciais et al. (2005) “Future climate warming is expected to enhance plant growth in temperate ecosystems and to increase carbon sequestration. But although severe regional heatwaves may become more frequent in a changing climate, their impact on terrestrial carbon cycling is unclear. Here we report measurements of ecosystem carbon dioxide fluxes, remotely sensed radiation absorbed by plants, and country-level crop yields taken during the European heatwave in 2003. We use a terrestrial biosphere simulation model to assess continental-scale changes in primary productivity during 2003, and their consequences for the net carbon balance. We estimate a 30 per cent reduction in gross primary productivity over Europe, which resulted in a strong anomalous net source of carbon dioxide (0.5 Pg C yr-1) to the atmosphere and reversed the effect of four years of net ecosystem carbon sequestration. Our results suggest that productivity reduction in eastern and western Europe can be explained by rainfall deficit and extreme summer heat, respectively. We also find that ecosystem respiration decreased together with gross primary productivity, rather than accelerating with the temperature rise. Model results, corroborated by historical records of crop yields, suggest that such a reduction in Europe’s primary productivity is unprecedented during the last century. An increase in future drought events could turn temperate ecosystems into carbon sources, contributing to positive carbon-climate feedbacks already anticipated in the tropics and at high latitudes.” Nature 437, 529-533 (22 September 2005) | doi:10.1038/nature03972. [Full text]

A Continuous Satellite-Derived Measure of Global Terrestrial Primary Production – Running et al. (2004) “Until recently, continuous monitoring of global vegetation productivity has not been possible because of technological limitations. This article introduces a new satellite-driven monitor of the global biosphere that regularly computes daily gross primary production (GPP) and annual net primary production (NPP) at 1-kilometer (km) resolution over 109,782,756 km2 of vegetated land surface. We summarize the history of global NPP science, as well as the derivation of this calculation, and current data production activity. The first data on NPP from the EOS (Earth Observing System) MODIS (Moderate Resolution Imaging Spectroradiometer) sensor are presented with different types of validation. We offer examples of how this new type of data set can serve ecological science, land management, and environmental policy. To enhance the use of these data by nonspecialists, we are now producing monthly anomaly maps for GPP and annual NPP that compare the current value with an 18-year average value for each pixel, clearly identifying regions where vegetation growth is higher or lower than normal.” BioScience, June 2004, Vol. 54, No. 6, Pages 547–560, doi:10.1641/0006-3568(2004)054[0547:ACSMOG]2.0.CO;2. [Full text]

Climate-Driven Increases in Global Terrestrial Net Primary Production from 1982 to 1999 – Nemani et al. (2003) “Recent climatic changes have enhanced plant growth in northern mid-latitudes and high latitudes. However, a comprehensive analysis of the impact of global climatic changes on vegetation productivity has not before been expressed in the context of variable limiting factors to plant growth. We present a global investigation of vegetation responses to climatic changes by analyzing 18 years (1982 to 1999) of both climatic data and satellite observations of vegetation activity. Our results indicate that global changes in climate have eased several critical climatic constraints to plant growth, such that net primary production increased 6% (3.4 petagrams of carbon over 18 years) globally. The largest increase was in tropical ecosystems. Amazon rain forests accounted for 42% of the global increase in net primary production, owing mainly to decreased cloud cover and the resulting increase in solar radiation.” Science 6 June 2003: Vol. 300. no. 5625, pp. 1560 – 1563, DOI: 10.1126/science.1082750. [Full text]

Terrestrial net primary production estimates for 0.5° grid cells from field observations—a contribution to global biogeochemical modeling – Zhang et al. (2003) “Net Primary Production (NPP) is an important component of the carbon cycle and, among the pools and fluxes that make up the cycle, it is one of the steps that are most accessible to field measurement. While easier than some other steps to measure, direct measurement of NPP is tedious and not practical for large areas and so models are generally used to study the carbon cycle at a global scale. Nevertheless these models require field measurements of NPP for parameterization, calibration and validation. Most NPP data are for relatively small field plots that cannot represent the 0.5° × 0.5° grid cells that are commonly used in global scale models. Furthermore, technical difficulties generally restrict NPP measurements to aboveground parts and sometimes do not even include all components of aboveground NPP. Thus direct inter-comparison between field data obtained in different studies or comparison of these results with coarse resolution model outputs can be misleading. We summarize and present a series of methods that were used by original authors to estimate NPP and how and what we have done to prepare a consistent data set of NPP for 0.5 °grid cells for a range of biomes from these studies. The methods used for estimation of NPP include: (i) aggregation of fine-scale (plot or stand-level) vegetation inventory data to larger grid cells, (ii) mapping of grid cells and area weighting of field NPP observations in each mapped class, (iii) direct correlation of extensive data sets of ground measurements with remotely sensed spectral vegetation indices, (iv) local modeling of NPP using key independent variables, for which maps are available at the scale of the grid cell, and (v) regression analysis to link productivity with controlling environmental variables. For a few grid cells whose NPP were obtained for multiple years, temporal analysis was conducted. The grid cells are grouped to the biome level and are compared with existing compilations of field NPP and the results of the Miami potential NPP model. Mean NPP was similar to the well-known compilation of Whittaker and Likens, except for temperate evergreen needle-leaved forest, woodland, and shrubland. The grid cell datasets are a contribution to the International Geosphere-Biosphere Programme (IGBP) Data and Information System (DIS) Global Primary Production Data Initiative (GPPDI). The full dataset currently contains 3654 cells (including replicate measurements) developed from 15 studies representing NPP in croplands, sparse vegetation, shrub lands, grasslands, and forests worldwide. An edited subset consists of 2335 cells in which outliers were removed and all replicate measurements were averaged for each unique geographical location. Most of the data incorporated into GPPDI were wholly or partly developed by participants in the GPPDI, in addition to the present authors. These studies are gathered together here to provide a consistent account of the grid cell component of GPPDI and an analysis of the entire data set. The datasets have been deposited in an IGBP-DIS GPPDI database (” Global Change Biology, Volume 9, Number 1, January 2003 , pp. 46-64(19), DOI: 10.1046/j.1365-2486.2003.00534.x.

Terrestrial net primary productivity – A brief history and a new worldwide database – Scurlock & Olson (2002) “Consistent data on terrestrial net primary productivity (NPP) are urgently needed to constrain model estimates of carbon fluxes and hence to refine our understanding of ecosystem responses to climate change. The NPP data have been collected in a coordinated manner for the past 30 years, but comprehensive summaries are rare. We report on the development and availability of a global NPP database that is suitable for modeling of the terrestrial carbon cycle at global and regional scales, for validation of remote sensing data, and for other applications. These data were obtained from the literature on ecophysiological field work and from detailed consultation with the scientific community. Data on NPP, biomass, and associated environmental variables are now publicly available for 53 detailed study sites, of which more than half have data for belowground biomass or biomass dynamics. Aboveground NPP ranges from 35 to 2320 g m–2a–1 (dry matter) and total NPP from 182 to 3538 g m–2a–1. Well-known but previously unobtainable compilations of data, such as the “Osnabrück Data Set” and the International Biological Program (IBP) Woodlands Data Set, are also incorporated in this database. Preliminary exploration of relationships between NPP and mean annual precipitation and temperature suggests that the new 53-site data collection, as well as the Osnabrück and IBP data, are all consistent with the historic “Miami” statistical model. These data are available from the Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC) for biogeochemical dynamics (see” Environ. Rev. 10(2): 91–109 (2002), doi:10.1139/a02-002.

Net primary production in tropical forests: an evaluation and synthesis of existing field data – Clark et al. (2001) “Information on net primary production in tropical forests is needed for the development of realistic global carbon budgets, for projecting how these ecosystems will be affected by climatic and atmospheric changes, and for evaluating eddy covariance measurements of tropical forest carbon flux. However, a review of the database commonly used to address these issues shows that it has serious flaws. In this paper we synthesize the data in the primary literature on NPP in old-growth tropical forests to produce a consistent data set on NPP for these forests. Studies in this biome have addressed only a few NPP components, all aboveground. Given the limited scope of the direct field measurements, we sought relationships in the existing data that allow estimation of unmeasured aspects of production from those that are more easily assessed. We found a predictive relationship between annual litterfall and aboveground biomass increment. For 39 diverse tropical forest sites, we then developed consistent, documented estimates of the upper and lower bounds around total NPP to serve as benchmarks for calibrating and validating biogeochemical models with respect to this biome. We developed these estimates based on existing field measurements, current understanding of aboveground consumption and biogenic volatile organic carbon emissions, and our judgment that belowground production is bounded by the range 0.2–1.2 × ANPP (aboveground NPP). Across this broad spectrum of tropical forests (dry to wet, lowland to montane, nutrient-rich to nutrient-poor soils), our estimates of lower and upper bounds on total NPP range from 1.7 to 11.8 Mg C·ha-1·yr-1 (lower bounds) and from 3.1 to 21.7 Mg C·ha-1·yr-1 (upper bounds). We also showed that two relationships that have been used for estimating NPP (the Bray-Gorham relationship based on leaf litterfall and the Miami model based on temperature or precipitation) are not valid for the tropical forest biome.” Ecological Applications, 11:371—384, doi:10.1890/1051-0761(2001)011[0371:NPPITF]2.0.CO;2. [Full text]

Primary Production of the Biosphere: Integrating Terrestrial and Oceanic Components – Field et al. (1998) “Integrating conceptually similar models of the growth of marine and terrestrial primary producers yielded an estimated global net primary production (NPP) of 104.9 petagrams of carbon per year, with roughly equal contributions from land and oceans. Approaches based on satellite indices of absorbed solar radiation indicate marked heterogeneity in NPP for both land and oceans, reflecting the influence of physical and ecological processes. The spatial and temporal distributions of ocean NPP are consistent with primary limitation by light, nutrients, and temperature. On land, water limitation imposes additional constraints. On land and ocean, progressive changes in NPP can result in altered carbon storage, although contrasts in mechanisms of carbon storage and rates of organic matter turnover result in a range of relations between carbon storage and changes in NPP.” Science 10 July 1998: Vol. 281. no. 5374, pp. 237 – 240, DOI: 10.1126/science.281.5374.237. [Full text]

Global Primary Production: A Remote Sensing Approach – Prince & Goward (1995) “A new model of global primary production (GLObal Production Efficiency Model, GLO-PEM), based on the production efficiency concept, is described. GLO-PEM is the first attempt to model both global net and gross primary production using the production efficiency approach and is unique in that it uses satellite data to measure both absorption of photosynthetically active radiation (APAR) and also the environmental variables that affect the utilization of APAR in primary production. The use of satellite measurements gives global, repetitive, spatially contiguous and time specific observations of the actual vegetation. GLO-PEM is based on physiological principles, in particular the amount of carbon fixed per unit absorbed photosynthetically active radiation ( epsilon ) is modelled rather than fitted using field observations. GLO-PEM is illustrated with the first available year (1987) of the 8 x 8 km resolution NOAA/NASA AVHRR land Pathfinder data set. The global net primary production, respiration and epsilon values obtained indicate that even the rather simple AVHRR provides a wealth of information relevant to biospheric monitoring. The algorithms and results presented indicate that there are significant possibilities of inferring biological and environmental variables using multispectral techniques that need to be explored if the new generation of satellite remote sensing systems is to be exploited productively.” Journal of Biogeography, Vol. 22, No. 4/5, Terrestrial Ecosystem Interactions with Global Change, Volume 2 (Jul. – Sep., 1995), pp. 815-835.

Terrestrial biogeochemical cycles: Global estimates with remote sensing – Schimel (1995) “The carbon and nitrogen cycles are crucial for understanding the changing Earth system, influencing atmospheric concentrations of greenhouse gases, primary productivity of the biosphere, and biogenic emissions of reactive trace species. The carbon budget of the terrestrial biosphere has attracted special attention because of its role in atmospheric changes in carbon dioxide. The terrestrial biosphere influences atmospheric CO2 through three main modes: First, large, nearly balanced fluxes of CO2 in photosynthesis and respiration exhibit a degree of interannual variability which can influence atmospheric CO2, at least on annual to decadal time scales. Second, land use changes release C02 to the atmosphere. Third, poorly understood processes are likely resulting in enhanced uptake of CO2 in certain ecosystems, acting as a sink in the global carbon cycle. This sink may result from forest demographics, atmospheric N deposition, or direct CO2 fertilization, or some synergistic combination of those processes. Global estimates of terrestrial carbon cycle components requires the use of remote observations; however, the appropriate remote sensing strategies are quite different for the various components.” Remote Sensing of Environment, Volume 51, Issue 1, January 1995, Pages 49-56, doi:10.1016/0034-4257(94)00064-T.

Global net primary production: Combining ecology and remote sensing – Field et al. (1995) “Terrestrial net primary production (NPP) is sensitive to a number of controls, including aspects of climate, topography, soils, plant and microbial characteristics, disturbance, and anthropogenic impacts. Yet, at least at the global scale, models based on very different types and numbers of parameters yield similar results. Part of the reason for this is that the major NPP controls influence each other, resulting, under current conditions, in broad correlations among controls. NPP models that include richer suites of controlling parameters should be more sensitive to conditions that disrupt the broad correlations, but the current paucity of global data limits the power of complex models. Improved data sets will facilitate applications of complex models, but many of the critical data are very difficult to produce, especially for applications dealing with the past or future. It may be possible to overcome some of the challenges of data availability through increased understanding and modeling of ecological processes that adjust plant physiology and architecture in relation to resources. The CASA (Carnegie, Stanford, Ames Approach) model introduced by Potter et al. (1993) and expanded here uses a combination of ecological principles, satellite data, and surface data to predict terrestrial NPP on a monthly time step. CASA calculates NPP as a product of absorbed photosynthetically active radiation, APAR, and an efficiency of radiation use, ε. The underlying postulate is that some of the limitations on NPP appear in each. CASA estimates annual terrestrial NPP to be 48 Pg and the maximum efficiency of PAR utilization (ε*) to be 0.39 g C MJ−1 PAR. Spatial and temporal variation in APAR is more than fivefold greater than variation in ε.” Remote Sensing of Environment, Volume 51, Issue 1, January 1995, Pages 74-88,doi:10.1016/0034-4257(94)00066-V.

Global climate change and terrestrial net primary production – Melillo et al. (1993) “A process-based model was used to estimate global patterns of net primary production and soil nitrogen cycling for contemporary climate conditions and current atmospheric C02 concentration. Over half of the global annual net primary production was estimated to occur in the tropics, with most of the production attributable to tropical evergreen forest. The effects of C02 doubling and associated climate changes were also explored. The responses in tropical and dry temperate ecosystems were dominated by C02, but those in northern and moist temperate ecosystems reflected the effects of temperature on nitrogen availability.” Nature 363, 234 – 240 (20 May 1993); doi:10.1038/363234a0. [Full text]

Potential Net Primary Productivity in South America: Application of a Global Model – Raich et al. (1991) “We use a mechanistically based ecosystem simulation model to describe and analyze the spatial and temporal patterns of terrestrial net primary productivity (NPP) in South America. The Terrestrial Ecosystem Model (TEM) is designed to predict major carbon and nitrogen fluxes and pool sizes in terrestrial ecosystems at continental to global scales. Information from intensively studies field sites is used in combination with continental—scale information on climate, soils, and vegetation to estimate NPP in each of 5888 non—wetland, 0.5° latitude °0.5° longitude grid cells in South America, at monthly time steps. Preliminary analyses are presented for the scenario of natural vegetation throughout the continent, as a prelude to evaluating human impacts on terrestrial NPP. The potential annual NPP of South America is estimated to be 12.5 Pg/yr of carbon (26.3 Pg/yr of organic matter) in a non—wetland area of 17.0 x 106 km2. More than 50% of this production occurs in the tropical and subtropical evergreen forest region. Six independent model runs, each based on an independently derived set of model parameters, generated mean annual NPP estimates for the tropical evergreen forest region ranging from 900 to 1510 g m-2 yr-1 of carbon, with an overall mean of 1170 g m-2 yr-1. Coefficients of variation in estimated annual NPP averaged 20% for any specific location in the evergreen forests, which is probably within the confidence limits of extant NPP measurements. Predicted rates of mean annual NPP in other types of vegetation ranged from 95 g m-2 yr-1 in arid shrublands to 930 g m-2 yr-1 in savannas, and were within the ranges measured in empirical studies. The spatial distribution of predicted NPP was directly compared with estimates made using the Miami mode of Lieth (1975). Overall, TEM predictions were ~10% lower than those of the Miami model, but the two models agreed closely on the spatial patterns of NPP in south America. Unlike previous models, however, TEM estimates NPP monthly, allowing for the evaluation of seasonal phenomena. This is an important step toward integration of ecosystem models with remotely sensed information, global climate models, and atmospheric transport models, all of which are evaluated at comparable spatial and temporal scales. Seasonal patterns of NPP in South America are correlated with moisture availability in most vegetation types, but are strongly influenced by seasonal differences in cloudiness in the tropical evergreen forests. On an annual basis, moisture availability was the factor that was correlated most strongly with annual NPP in South America, but differences were again observed among vegetation types. These results allow for the investigation and analysis of climatic controls over NPP at continental scales, within and among vegetation types, and within years. Further model validation is needed. Nevertheless, the ability to investigate NPP—environment interactions with a high spatial and temporal resolution at continental scales should prove useful if not essential for rigorous analysis of the potential effects of global climate changes on terrestrial ecosystems.” Ecological Applications. 1:399—429, doi:10.2307/1941899. [Full text]

Mapping Regional Forest Evapotranspiration and Photosynthesis by Coupling Satellite Data with Ecosystem Simulation – Running et al. (1989) “Annual evapotranspiration (ET) and net photosynthesis (PSN) were estimated for a mountainous 28 x 55 km region of predominantly coniferous forests in western Montana. A simple geographic information system integrated topographic, soils, vegetation, and climatic data at a 1.1 -km scale size defined by the satellite sensor pixel size. Leaf area index (LAI) of the forest was estimated with data from the NOAA (National Oceanic and Atmospheric Administration) Advanced Very High Resolution Radiometer (AVHRR). Daily microclimate of each cell was estimated from ground and satellite data and interpolated using MT-CLIM, a mountain microclimate simulator. A forest ecosystem simulation model, FOREST-BGC. was used to calculate ET and PSN daily for each cell. Ranges of estimated LA1 (4-U) ET (25-60 cm/yr), and PSN (9-20 Mg ha-1 yr-1) across the landscape follow the trends expected in both magnitude and spatial pattern. These estimates compared well with field measurements of related variables, although absolute validation of these predictions is not now possible at large spatial scales.” Ecology, Vol. 70, No. 4 (Aug., 1989), pp. 1090-1101. [Full text]

Relating seasonal patterns of the AVHRR vegetation index to simulated photosynthesis and transpiration of forests in different climates – Running & Nemani (1988) “Recent research has suggested that the Normalized Difference Vegetation Index (NDVI) calculated from the AVHRR sensor is directly related to photosynthesis (PSN), transpiration (TRAN), and aboveground net primary production (ANPP) of terrestrial vegetation. Weekly NDVI data for 1983–1984 were retrieved for seven sites of diverse climate in North America. The sites were Fairbanks, AK, Seattle, WA, Missoula, MT, Madison, WI, Knoxville, TN, Jacksonville, FL, and Tucson, AZ. Meteorological data from ground stations were retrieved to drive an ecosystem simulation model (FOREST-BGC) calculating daily canopy PSN and TRAN and annual ANPP of a hypothetical forest stand for the corresponding period at each site. Correlations of annual integrated NDVI across all sites for both years were: annual PSN, R2 = 0.87; annual TRAN, R2 = 0.77; annual ANPP, R2 = 0.72. Correlation between weekly NDVI and PSN was variable; with high latitude wet sites, R2 = 0.77–0.84. On sites with less seasonal amplitude of NDVI and PSN, or on sites with substantial seasonal water stress correlations ranged from R2 = 0.08 to 0.64. Correlations of weekly NDVI with TRAN followed the same pattern as PSN, but were slightly lower. The tendency of raw NDVI data to overpredict PSN and TRAN on water limited sites was partially corrected using an “aridity index” of annual radiation/annual precipitation that could be computed from general climatological data for improving large scale NDVI maps of PSN and TRAN. The spatial subsampling done for the global vegetation index (GVI) precludes following specific study sites through the growing season. We conclude that estimates of vegetation productivity using the GVI should only be done as annual integrations until unsubsampled local area coverage (LAC) NDVI data can be tested against forest PSN, TRAN, and ANPP, measured at shorter time intervals.” Remote Sensing of Environment, Volume 24, Issue 2, March 1988, Pages 347-367, doi:10.1016/0034-4257(88)90034-X. [Full text]

North American vegetation patterns observed with the NOAA-7 advanced very high resolution radiometer – Goward et al. (1985) “Spectral vegetation index measurements derived from remotely sensed observations show great promise as a means to improve knowledge of land vegetation patterns. The daily, global observations acquired by the Advanced Very High Resolution Radiometer, a sensor on the current series of U.S. National Oceanic and Atmospheric Administration meteorological satellites, may be particularly well suited for global studies of vegetation. Preliminary results from analysis of North American observations, extending from April to November 1982, show that the vegetation index patterns observed correspond to the known seasonality of North American natural and cultivated vegetation. Integration of the observations over the growing season produced measurements that are related to net primary productivity patterns of the major North American natural vegetation formations. Regions of intense cultivation were observed as anomalous areas in the integrated growing season measurements. These anomalies can be explained by contrasts between cultivation practices and natural vegetation phenology. Major new information on seasonality, annual extent and interannual variability of vegetation photosynthetic activity at continental and global scales can be derived from these satellite observations.” Plant Ecology, Volume 64, Number 1, 3-14, DOI: 10.1007/BF00033449. [Full text]

Closely related

Science shocker: Drought drives decade-long decline in plant growth – Climate Progress (2010)

Posted in Global warming effects | 4 Comments »

Papers on ecosystem response to past climate

Posted by Ari Jokimäki on March 22, 2010

This is a list of papers on ecosystem response to past climate changes. This subject was suggested by J Bowers in this thread. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (June 10, 2010): Root et al. (2003) added.
UPDATE (May 22, 2010): Woolridge (2008) added, thanks to J Bowers for pointing it out (see the comment section below).

Fossil Plant Relative Abundances Indicate Sudden Loss of Late Triassic Biodiversity in East Greenland – McElwain et al. (2009) “The pace of Late Triassic (LT) biodiversity loss is uncertain, yet it could help to decipher causal mechanisms of mass extinction. We investigated relative abundance distributions (RADs) of six LT plant assemblages from the Kap Stewart Group, East Greenland, to determine the pace of collapse of LT primary productivity. RADs displayed not simply decreases in the number of taxa, but decreases in the number of common taxa. Likelihood tests rejected a hypothesis of continuously declining diversity. Instead, the RAD shift occurred over the upper two-to-four fossil plant assemblages and most likely over the last three (final 13 meters), coinciding with increased atmospheric carbon dioxide concentration and global warming. Thus, although the LT event did not induce mass extinction of plant families, it accompanied major and abrupt change in their ecology and diversity. “ [Full text]

A long-term association between global temperature and biodiversity, origination and extinction in the fossil record – Mayhew et al. (2008) “We analysed the fossil record for the last 520 Myr against estimates of low latitude sea surface temperature for the same period. We found that global biodiversity (the richness of families and genera) is related to temperature and has been relatively low during warm ‘greenhouse’ phases, while during the same phases extinction and origination rates of taxonomic lineages have been relatively high. These findings are consistent for terrestrial and marine environments and are robust to a number of alternative assumptions and potential biases. Our results provide the first clear evidence that global climate may explain substantial variation in the fossil record in a simple and consistent manner.” [Full text]

The palaeoclimatology, palaeoecology and palaeoenvironmental analysis of mass extinction events – Twitchett (2006) “Many aspects of these [mass extinction] events are still debated and there is no common cause or single set of climatic or environmental changes common to these five events, although all are associated with evidence for climatic change. … The environmental consequences of rapid global warming (such as ocean stagnation, reduced upwelling and loss of surface productivity) are considered to have been particularly detrimental to the biosphere in the geological past. The first phase of the Late Ordovician event is clearly linked to rapid global cooling.” [Full text]

Nannoplankton Extinction and Origination Across the Paleocene-Eocene Thermal Maximum – Gibbs et al. (2006) “The Paleocene-Eocene Thermal Maximum (PETM, 55 million years ago) was an interval of global warming and ocean acidification attributed to rapid release and oxidation of buried carbon. We show that the onset of the PETM coincided with a prominent increase in the origination and extinction of calcareous phytoplankton. Yet major perturbation of the surface-water saturation state across the PETM was not detrimental to the survival of most calcareous nannoplankton taxa and did not impart a calcification or ecological bias to the pattern of evolutionary turnover. Instead, the rate of environmental change appears to have driven turnover, preferentially affecting rare taxa living close to their viable limits.” [Full text]

Exceptional record of mid-Pleistocene vertebrates helps differentiate climatic from anthropogenic ecosystem perturbations – Barnosky et al. (2004) “We report on a uniquely rich mid-Pleistocene vertebrate sequence from Porcupine Cave, Colorado, which records at least 127 species and the earliest appearances of 30 mammals and birds. By analyzing >20,000 mammal fossils in relation to modern species and independent climatic proxies, we determined how mammal communities reacted to presumed glacial–interglacial transitions between 1,000,000 and 600,000 years ago. We conclude that climatic warming primarily affected mammals of lower trophic and size categories, in contrast to documented human impacts on higher trophic and size categories historically. Despite changes in species composition and minor changes in small-mammal species richness evident at times of climatic change, overall structural stability of mammal communities persisted >600,000 years before human impacts.” [Full text]

Did impacts, volcanic eruptions, or climate change affect mammalian evolution? – Prothero (2004) “Two different Cenozoic mammal diversity curves were compared, and important climatic, volcanic, and impact horizons were examined in detail. In no case is there a strong correlation between impacts, eruptions, or climatic events and any episode of mammalian turnover. On the contrary, most of the known impact, eruption, and climatic events of the Cenozoic occurred during intervals of faunal stability. Conversely, episodes of high turnover and faunal change among Cenozoic mammals correlate with no known extrinsic causes. Apparently, extrinsic environmental factors such as impacts, eruptions, and climate change have a minimal effect, and intrinsic biological factors must be more important.”

How to kill (almost) all life: the end-Permian extinction event – Benton & Twitchett (2003) “The biggest mass extinction of the past 600 million years (My), the end-Permian event (251 My ago), witnessed the loss of as much as 95% of all species on Earth. Key questions for biologists concern what combination of environmental changes could possibly have had such a devastating effect, the scale and pattern of species loss, and the nature of the recovery. New studies on dating the event, contemporary volcanic activity, and the anatomy of the environmental crisis have changed our perspectives dramatically in the past five years. Evidence on causation is equivocal, with support for either an asteroid impact or mass volcanism, but the latter seems most probable. The extinction model involves global warming by 6°C and huge input of light carbon into the ocean-atmosphere system from the eruptions, but especially from gas hydrates, leading to an ever-worsening positive-feedback loop, the ‘runaway greenhouse’.” [Full text]

Correlated terrestrial and marine evidence for global climate changes before mass extinction at the Cretaceous–Paleogene boundary – Wilf et al. (2003) “Both plants and foraminifera indicate warming near 66.0 Ma, a warming peak from ≈65.8 to 65.6 Ma, and cooling near 65.6 Ma, suggesting that these were global climate shifts. The warming peak coincides with the immigration of a thermophilic flora, maximum plant diversity, and the poleward range expansion of thermophilic foraminifera. … To the extent that biodiversity is correlated with temperature, estimates of the severity of end-Cretaceous extinctions that are based on occurrence data from the warming peak are probably inflated, as we illustrate for North Dakota plants. However, our analysis of climate and facies considerations shows that the effects of bolide impact should be regarded as the most significant contributor to these plant extinctions.” [Full text]

Mammalian Response to Global Warming on Varied Temporal Scales – Barnosky et al. (2003) “Paleontological information was used to evaluate and compare how Rocky Mountain mammalian communities changed during past global warming events characterized by different durations (350, ;10,000–20,000, and 4 million years) and different per–100-year warming rates (1.08C, 0.18C, 0.06–0.088C, 0.0002–0.00038C per 100 years). … Nevertheless, examination of past global warming episodes suggested that approximately concurrent with warming, a predictable sequence of biotic events occurs at the regional scale of the central and northern United States Rocky Mountains. First, phenotypic and density changes in populations are detectable within 100 years. Extinction of some species, noticeable changes in taxonomic composition of communities, and possibly reduction in species richness follow as warming extends to a few thousand years. Faunal turnover nears 100% and species diversity may increase when warm temperatures last hundreds of thousands to millions of years, because speciation takes place and faunal changes initiated by a variety of shorter-term processes accumulate. Climate-induced faunal changes reported for the current global warming episode probably do not yet exceed the normal background rate, but continued warming during the next few decades, especially combined with the many other pressures of humans on natural ecosystems, has a high probability of producing effects that have not been experienced often, if ever, in mammalian history.” [Full text]

Fingerprints of global warming on wild animals and plants – Root et al. (2003) “We gathered information on species and global warming from 143 studies for our meta-analyses. These analyses reveal a consistent temperature-related shift, or ‘fingerprint’, in species ranging from molluscs to mammals and from grasses to trees. Indeed, more than 80% of the species that show changes are shifting in the direction expected on the basis of known physiological constraints of species. Consequently, the balance of evidence from these studies strongly suggests that a significant impact of global warming is already discernible in animal and plant populations.”

Earth’s biggest ‘whodunnit’: unravelling the clues in the case of the end–Permian mass extinction – White (2002) “The mass extinction that occurred at the end of the Permian period, 250 million years ago, was the most devastating loss of life that Earth has ever experienced. It is estimated that ca. 96% of marine species were wiped out and land plants, reptiles, amphibians and insects also suffered. The causes of this catastrophic event are currently a topic of intense debate. The geological record points to significant environmental disturbances, for example, global warming and stagnation of ocean water.” [Full text]

Global Climate Change and North American Mammalian Evolution – Alroy et al. (2000) “We compare refined data sets for Atlantic benthic foraminiferal oxygen isotope ratios and for North American mammalian diversity, faunal turnover, and body mass distributions. Each data set spans the late Paleocene through Pleistocene and has temporal resolution of 1.0 m.y. … Some of the major climate shifts indicated by oxygen isotope records do correspond to major ecological and evolutionary transitions in the mammalian biota, but the nature of these correspondences is unpredictable, and several other such transitions occur at times of relatively little global climate change. We conclude that given currently available climate records, we cannot show that the impact of climate change on the broad patterns of mammalian evolution involves linear forcings; instead, we see only the relatively unpredictable effects of a few major events.” [Full text]

Fossil Plants and Global Warming at the Triassic-Jurassic Boundary – McElwain et al. (1999) “The Triassic-Jurassic boundary marks a major faunal mass extinction, but records of accompanying environmental changes are limited. Paleobotanical evidence indicates a fourfold increase in atmospheric carbon dioxide concentration and suggests an associated 3° to 4°C “greenhouse” warming across the boundary. These environmental conditions are calculated to have raised leaf temperatures above a highly conserved lethal limit, perhaps contributing to the >95 percent species-level turnover of Triassic-Jurassic megaflora.”

Abrupt Climate Change and Extinction Events in Earth History – Crowley & North (1988) “There is a growing body of theoretical and empirical support for the concept of abrupt climate change, and a comparison of paleoclimate data with the Phanerozoic extinction record indicates that climate and biotic transitions often coincide. … Our analysis suggests that a terrestrially induced climate instability is a viable mechanism for causing rapid environmental change and biotic turnover in earth history, but the relation is not so strong that other sources of variance can be excluded.” [Full text]

Temperature and biotic crises in the marine realm – Stanley (1984) “Climatic change has been a prominent cause of marine mass extinction, but areal restriction of seafloor during global regression has not. Late Eocene and Pliocene-Pleistocene cooling, for example, caused major extinctions, but profound global Oligocene and Pleistocene regressions had little or no direct effect on benthic diversity. Recurrent themes of pre-Cenozoic marine crises suggest that global temperature change also served as a major, and perhaps dominant, agent of extinction in these events: (1) Mass extinctions have frequently been concentrated in the tropics, which seem to have become a refrigerated trap from which there has been no escape; biotas previously occupying high latitudes have shifted equatorward, to replace disappearing tropical biotas. (2) Some crises were not instantaneous but followed protracted and pulsatile temporal patterns, as would be predicted for complex, global climatic crises. (3) Several mass extinctions coincided with recognized intervals of climatic cooling.”

Closely related

Mass extinctions past and present: a unifying hypothesis – Woolridge (2008) Note that the peer review of this paper was interrupted (see the interactive discussion linked in the abstract page) but I include this paper to show this hypothesis. “Here, it is proposed that the pH-dependent inactivation of a single enzyme, urease, provides a unifying kill-mechanism for at least four of the “big five” mass extinctions of the past 560 million years. The triggering of this kill-mechanism is suggested to be sensitive to both gradualistic and catastrophic environmental disturbances that cause the operating pH of urease-dependent organisms to cross enzymatic “dead zones”, one of which is suggested to exist at ~pH 7.9. For a wide range of oceanic and terrestrial ecosystems, this pH threshold coincides with an atmospheric CO2 partial pressure (pCO2) of ~560 ppmv – a level that at current CO2 emission trajectories may be exceeded as early as 2050.” [Full text]

Documenting a significant relationship between macroevolutionary origination rates and Phanerozoic pCO2 levels – Cornette et al. (2002) “We show that the rates of diversification of the marine fauna and the levels of atmospheric CO2 have been closely correlated for the past 545 million years. … The strength of the correlation suggests that one or more environmental variables controlling CO2 levels have had a profound impact on evolution throughout the history of metazoan life.” [Full text]

Global biodiversity and the ancient carbon cycle – Rothman (2001) “Paleontological data for the diversity of marine animals and land plants are shown to correlate significantly with a concurrent measure of stable carbon isotope fractionation for approximately the last 400 million years.” [Full text]

Posted in AGW evidence, Global warming effects | 11 Comments »

Papers on polar bear populations

Posted by Ari Jokimäki on March 15, 2010

This is a list of papers on polar bear populations. Emphasis is on climate change effect on the populations. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (June 9, 2012): Stirling & Derocher (2012), Stirling & Parkinson (2006), Stirling et al. (1999), and Stirling & Derocher (1993) added.
UPDATE (October 15, 2010): Regehr et al. (2006) added. Thanks to Barry for pointing it out, see the comment section below.

Effects of Climate Warming on Polar Bears: A Review of the Evidence – Stirling & Derocher (2012) “Climate warming is causing unidirectional changes to annual patterns of sea ice distribution, structure, and freeze-up. We summarize evidence that documents how loss of sea ice, the primary habitat of polar bears (Ursus maritimus), negatively affects their long-term survival. To maintain viable subpopulations, polar bears depend upon sea ice as a platform from which to hunt seals for long enough each year to accumulate sufficient energy (fat) to survive periods when seals are unavailable. Less time to access to prey, because of progressively earlier breakup in spring, when newly-weaned ringed seal (Pusa hispida) young are available, results in longer periods of fasting, lower body condition, decreased access to denning areas, fewer and smaller cubs, lower survival of cubs as well as bears of other age classes and, finally, subpopulation decline toward eventual extirpation. The chronology of climate-driven changes will vary between subpopulations, with quantifiable negative effects being documented first in the more southerly subpopulations, such as those in Hudson Bay or the southern Beaufort Sea. As the bears’ body condition declines, more seek alternate food resources so the frequency of conflicts between bears and humans increases. In the most northerly areas, thick multiyear ice, through which little light penetrates to stimulate biological growth on the underside, will be replaced by annual ice which facilitates greater productivity and may create habitat more favorable to polar bears over continental shelf areas in the short term. If the climate continues to warm and eliminate sea ice as predicted, polar bears will largely disappear from the southern portions of their range by mid-century. They may persist in the northern Canadian Arctic Islands and northern Greenland for the foreseeable future, but their long-term viability, with a much reduced global population size in a remnant of their former range, is uncertain.” Ian Stirling, Andrew E. Derocher, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02753.x.

Predicting 21st-century polar bear habitat distribution from global climate models – Durner et al. (2009) “We used location data from satellite-collared polar bears and environmental data (e.g., bathymetry, distance to coastlines, and sea ice) collected from 1985 to 1995 to build resource selection functions (RSFs). … We applied the RSFs to monthly maps of 21st-century sea ice concentration projected by 10 general circulation models (GCMs) used in the Intergovernmental Panel of Climate Change Fourth Assessment Report, under the A1B greenhouse gas forcing scenario. … Mean loss of optimal polar bear habitat was greatest during summer; from an observed 1.0 million km2 in 1985–1995 (baseline) to a projected multi-model mean of 0.32 million km2 in 2090–2099 (−68% change). Projected winter losses of polar bear habitat were less: from 1.7 million km2 in 1985–1995 to 1.4 million km2 in 2090–2099 (−17% change). … Although a reduction in the total amount of optimal habitat will likely reduce polar bear populations, exact relationships between habitat losses and population demographics remain unknown.” [Full text]

Rebuttal of “Polar Bear Population Forecasts: A Public-Policy Forecasting Audit” – Amstrup et al. (2009) “In summary, we show that the AGS audit offers no valid criticism of the USGS conclusion that global warming poses a serious threat to the future welfare of polar bears and that it only serves to distract from reasoned public-policy debate.” [Full text]

Effects of climate change on polar bears – Wiig et al. (2008) A review article. “In this article, we review the effects on polar bears of global warming that have already been observed, and try to evaluate what may happen to the polar bears in the future. Many researchers have predicted a wide range of impacts of climate change on polar bear demography and conditions. A predicted major reduction in sea ice habitat will reduce the availability of ice associated seals, the main prey of polar bears, and a loss and fragmentation of polar bear habitat will ultimately lead to large future reductions in most subpopulations. It is likely that polar bears will be lost from many areas where they are common today and also that the total population will change into a few more distinctly isolated populations.”

Effects of Earlier Sea Ice Breakup on Survival and Population Size of Polar Bears in Western Hudson Bay – Regehr et al. (2007) “We used a flexible extension of Cormack–Jolly–Seber capture–recapture models to estimate population size and survival for polar bears (Ursus maritimus), one of the most ice-dependent of Arctic marine mammals. We analyzed data for polar bears captured from 1984 to 2004 along the western coast of Hudson Bay and in the community of Churchill, Manitoba, Canada. The Western Hudson Bay polar bear population declined from 1,194 (95% CI = 1,020–1,368) in 1987 to 935 (95% CI = 794–1,076) in 2004. … Survival of juvenile, subadult, and senescent-adult polar bears was correlated with spring sea ice breakup date, which was variable among years and occurred approximately 3 weeks earlier in 2004 than in 1984. We propose that this correlation provides evidence for a causal association between earlier sea ice breakup (due to climatic warming) and decreased polar bear survival.”

Polar Bear Population Status in the Southern Beaufort Sea – Regehr et al. (2006) An U.S. Geological Survey report. “Polar bears depend entirely on sea ice for survival. In recent years, a warming climate has caused major changes in the Arctic sea ice environment, leading to concerns regarding the status of polar bear populations. Here we present findings from long-term studies of polar bears in the southern Beaufort Sea (SBS) region of the U.S. and Canada, which are relevant to these concerns. We applied open population capture-recapture models to data collected from 2001 to 2006, and estimated there were 1,526 (95% CI = 1,211; 1,841) polar bears in the SBS region in 2006. The number of polar bears in this region was previously estimated to be approximately 1,800. Because precision of earlier estimates was low, our current estimate of population size and the earlier ones cannot be statistically differentiated. For the 2001–06 period, the best fitting capture-recapture model provided estimates of total apparent survival of 0.43 for cubs of the year (COYs), and 0.92 for all polar bears older than COYs. Because the survival rates for older polar bears included multiple sex and age strata, they could not be compared to previous estimates. Survival rates for COYs, however, were significantly lower than estimates derived in earlier studies (P = 0.03). The lower survival of COYs was corroborated by a comparison of the number of COYs per adult female for periods before (1967–89) and after (1990–2006) the winter of 1989–90, when warming temperatures and altered atmospheric circulation caused an abrupt change in sea ice conditions in the Arctic basin. In the latter period, there were significantly more COYs per adult female in the spring (P = 0.02), and significantly fewer COYs per adult female in the autumn (P < 0.001). Apparently, cub production was higher in the latter period, but fewer cubs survived beyond the first 6 months of life. Parallel with declining survival, skull measurements suggested that COYs captured from 1990 to 2006 were smaller than those captured before 1990. Similarly, both skull measurements and body weights suggested that adult males captured from 1990 to 2006 were smaller than those captured before 1990. The smaller stature of males was especially notable because it corresponded with a higher mean age of adult males. Male polar bears continue to grow into their teens, and if adequately nourished, the older males captured in the latter period should have been larger than those captured earlier. In western Hudson Bay, Canada, a significant decline in population size was preceded by observed declines in cub survival and physical stature. The evidence of declining recruitment and body size reported here, therefore, suggests vigilance regarding the future of polar bears in the SBS region." [Full text]

Possible Effects of Climate Warming on Selected Populations of Polar Bears (Ursus maritimus) in the Canadian Arctic – Stirling & Parkinson (2006) “Polar bears depend on sea ice for survival. Climate warming in the Arctic has caused significant declines in total cover and thickness of sea ice in the polar basin and progressively earlier breakup in some areas. Inuit hunters in the areas of four polar bear populations in the eastern Canadian Arctic (including Western Hudson Bay) have reported seeing more bears near settlements during the open-water period in recent years. In a fifth ecologically similar population, no changes have yet been reported by Inuit hunters. These observations, interpreted as evidence of increasing population size, have resulted in increases in hunting quotas. However, long-term data on the population size and body condition of polar bears in Western Hudson Bay, as well as population and harvest data from Baffin Bay, make it clear that those two populations at least are more likely to be declining, not increasing. While the ecological details vary in the regions occupied by the five different populations discussed in this paper, analysis of passive-microwave satellite imagery beginning in the late 1970s indicates that the sea ice is breaking up at progressively earlier dates, so that bears must fast for longer periods during the open-water season. Thus, at least part of the explanation for the appearance of more bears near coastal communities and hunting camps is likely that they are searching for alternative food sources in years when their stored body fat depots may be depleted before freeze-up, when they can return to the sea ice to hunt seals again. We hypothesize that, if the climate continues to warm as projected by the Intergovernmental Panel on Climate Change (IPCC), then polar bears in all five populations discussed in this paper will be increasingly food-stressed, and their numbers are likely to decline eventually, probably significantly so. As these populations decline, problem interactions between bears and humans will likely continue, and possibly increase, as the bears seek alternative food sources. Taken together, the data reported in this paper suggest that a precautionary approach be taken to the harvesting of polar bears and that the potential effects of climate warming be incorporated into planning for the management and conservation of this species throughout the Arctic.” Ian Stirling and Claire L. Parkinson, Arctic, Vol. 59, No. 3 (Sep., 2006), pp. 261-275 [Full text]

Observations of mortality associated with extended open-water swimming by polar bears in the Alaskan Beaufort Sea – Monnett & Gleason (2006) “We speculate that mortalities due to offshore swimming during late-ice (or mild ice) years may be an important and unaccounted source of natural mortality given energetic demands placed on individual bears engaged in long-distance swimming. We further suggest that drowning-related deaths of polar bears may increase in the future if the observed trend of regression of pack ice and/or longer open water periods continues.” [Full text]

The influence of climate variability on polar bear (Ursus maritimus) and ringed seal (Pusa hispida) population dynamics – Rosing-Asvid (2006) “Unusually high polar bear (Ursus maritimus Phipps, 1774) predation on ringed seal (Pusa hispida (Schreber, 1775)) pups and increased survival of polar bear cubs during mild springs is documented in published articles. Strong predation on newborn ringed seal pups in early spring, however, is likely to lower the overall energy intake of polar bears if ringed seal pups are their main food, because the energetic value of ringed seal pups increases 7–8 times during the 6 week lactation period. So although hunting success in early spring increases cub survival during the period after den emergence,when they are most vulnerable, it is likely to increase the number of starving bears later in the season.” [Full text]

Population ecology of polar bears at Svalbard, Norway – Derocher (2005) “The population ecology of polar bears at Svalbard, Norway, was examined from 1988 to 2002 using live-captured animals. … However, the variation in reproduction and body mass in the population show a relationship between large-scale climatic variation and the upper trophic level in an Arctic marine ecosystem. Similar change in other polar bear populations has been attributed to climate change, and further research is needed to establish linkages between climate and the population ecology of polar bears.” [Full text]

Polar Bears in a Warming Climate – Derocher et al. (2004) “Polar bears (Ursus maritimus) live throughout the ice-covered waters of the circumpolar Arctic, particularly in near shore annual ice over the continental shelf where biological productivity is highest. However, to a large degree under scenarios predicted by climate change models, these preferred sea ice habitats will be substantially altered. … In the short term, climatic warming may improve bear and seal habitats in higher latitudes over continental shelves if currently thick multiyear ice is replaced by annual ice with more leads, making it more suitable for seals. … The effects of climate change are likely to show large geographic, temporal and even individual differences and be highly variable, making it difficult to develop adequate monitoring and research programs. All ursids show behavioural plasticity but given the rapid pace of ecological change in the Arctic, the long generation time, and the highly specialised nature of polar bears, it is unlikely that polar bears will survive as a species if the sea ice disappears completely as has been predicted by some.” [Full text]

Polar Bear Distribution and Abundance on the Southwestern Hudson Bay Coast During Open Water Season, in Relation to Population Trends and Annual Ice Patterns – Stirling et al. (2004) “We concluded that 1) the coastal survey data reliably indicated the population trends in Manitoba and Ontario; 2) little exchange occurred between the Western Hudson Bay (Manitoba) and Southern Hudson Bay (Ontario) populations; 3) between 1971 and 2001, there was a statistically significant trend toward earlier breakup of sea ice off the Manitoba coast, but not off the Ontario coast; 4) the onset of ice absence along the coast had no significant relationship to the number of bears present in each sub-sampling area within either the Manitoba or the Ontario population, but did significantly influence the distribution of bears on the coastline of each province independently of the other; 5) timing of the surveys can influence the results; and 6) adult male and female bears both showed a high degree of fidelity to specific areas during summer, independent of the pattern of ice breakup.” [Full text]

Polar Bears and Seals in the Eastern Beaufort Sea and Amundsen Gulf: A Synthesis of Population Trends and Ecological Relationships over Three Decades – Stirling (2002) “The changes in the sea ice environment, and their consequent effects on polar bears, are demonstrable in parallel fluctuations in the mean ages of polar bears killed each year by Inuit hunters. In 1989, the decadal-scale pattern in fluctuations of ice conditions in the eastern Beaufort Sea changed in response to oceanographic and climatic factors, and this change has resulted in greater amounts of open water in recent years. In addition, climatic warming will be a major environmental factor if greenhouse gas emissions continue to increase. It is unknown whether the ecosystem will return to the pattern of decadal-scale change exhibited in previous decades, or how polar bears and seals will respond to ecological changes in the future, but research on these topics is a high priority.” [Full text]

Long-Term Trends in the Population Ecology of Polar Bears in Western Hudson Bay in Relation to Climatic Change – Stirling et al. (1999) “From 1981 through 1998, the condition of adult male and female polar bears has declined significantly in western Hudson Bay, as have natality and the proportion of yearling cubs caught during the open water period that were independent at the time of capture. Over this same period, the breakup of the sea ice on western Hudson Bay has been occurring earlier. There was a significant positive relationship between the time of breakup and the condition of adult females (i.e., the earlier the breakup, the poorer the condition of the bears). The trend toward earlier breakup was also correlated with rising spring air temperatures over the study area from 1950 to 1990. We suggest that the proximate cause of the decline in physical and reproductive parameters of polar bears in western Hudson Bay over the last 19 years has been a trend toward earlier breakup, which has caused the bears to come ashore in progressively poorer condition. The ultimate factor responsible for the earlier breakup in western Hudson Bay appears to be a long-term warming trend in April-June atmospheric temperatures.” Ian Stirling, Nicholas J. Lunn and John Iacozza, Arctic, Vol. 52, No. 3 (Sep., 1999), pp. 294-306.

Possible Impacts of Climatic Warming on Polar Bears – Stirling & Derocher (1993) “If climatic warming occurs, the first impacts on polar bears (Ursus maritimus) will be felt at the southern limits of their distribution, such as in James and Hudson bays, where the whole population is already forced to fast for approximately four months when the sea ice melts during the summer. Prolonging the ice-free period will increase nutritional stress on this population until they are no longer able to store enough fat to survive the ice-free period. Early signs of impact will include declining body condition, lowered reproductive rates, reduced survival of cubs, and an increase in polar bear-human interactions. Although most of these changes are currently detectable in the polar bears of western Hudson Bay, it cannot yet be determined if climatic change is involved. In the High Arctic, a decrease in ice cover may stimulate an initial increase in biological productivity. Eventually however, it is likely that seal populations will decline wherever the quality and availability of breeding habitat are reduced. Rain during the late winter may cause polar bear maternity dens to collapse, causing the death of occupants. Human-bear problems will increase as the open water period becomes longer and bears fasting and relying on their fat reserves become food stressed. If populations of polar bears decline, harvest quotas for native people will be reduced and eventually eliminated. Tourism based on viewing polar bears would become extirpated from at least the southern part of their range. If climatic warming occurs, the polar bear is an ideal species through which to monitor the cumulative effects in arctic marine ecosystems because of its position at the top of the arctic marine food chain.” Ian Stirling and Andrew E. Derocher, Arctic, Vol. 46, No. 3 (Sep., 1993), pp. 240-245. [Full text]

Posted in Climate claims, Global warming effects | 5 Comments »


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