Final Report Summary - POLARCLIMSTRESS (Climate change, energetic constraints and susceptibility to environmental stressors in Antarctic seabirds: integrating stress physiology and population heteroge
Project objectives
The aim of the project was to investigate how ongoing climate change could affect vertebrates and, more specifically, birds. This question is crucial because it remains very unclear why some species can adjust to environmental changes whereas others cannot. Indeed, numerous studies have reported population trends (declines, stability and even increases in a few cases) in relation to climate change, but overall our knowledge of the mechanisms that determine the ability of vertebrates to cope with these changes remains poor. As specified in the initial proposal, the project aimed to understand how environmental variables could affect the performances of birds and which physiological mechanisms can play a major role in the ability of birds to cope with ongoing environmental changes.
Project results
During this fellowship, we conducted several studies to reach the project objectives. We combined experimental approaches using captive birds in the USA and field work on Antarctic seabirds in order to better understand what mechanisms are involved in the adjustment of vertebrates to environmental changes. In addition, we developed and used new laboratory techniques in ecology to investigate in detail the physiological mechanisms that may be involved in such adjustments. These developments have been performed in the USA, and the fellow transferred this knowledge to the European institution during the return phase. All these steps were done in collaboration with all the institutions involved in the POLARCLIMSTRESS project (Prof. John C. Wingfield, UC Davis, Prof. Carol M. Vleck, Iowa State University, and Dr Olivier Chastel, CEBC-CNRS). We have disseminated the results from the fellow's studies via publications in scientific journals, conferences and also through some mentoring (undergraduate students).
This project allowed us to improve our understanding of the mechanisms that can link population trends and climate change. First, we first examined in the field how and why some species are affected by climate change. For instance, we showed that warmer temperatures during the breeding season can pose a major threat to reproductive success in some Antarctic seabirds due to unusual snow melting and precipitations. Warm temperatures resulted in flooding of the nests and total breeding failure for many individuals. We also showed that the quality of the nest site can potentially attenuate the negative effects of warm temperatures on breeding performances (especially if parents built their nests in well-drained areas). Importantly, global climate change predicts that major swings in intensity, frequency and duration of storms will increase in the near future, often accompanied by new, record-high temperatures. Therefore, climate change will increase the possibility that flowing water during the breeding season may pose a major threat to the reproductive success of some Antarctic seabirds.
Furthermore, we demonstrated that climate change can also have negative impacts on temperate species. We reported that a prolonged drought reduces bird performances on the wintering ground and that these negative effects can be temporarily attenuated by the quality of the habitat. Our results therefore show that birds from different areas can be affected by climate changes and that habitat degradation may accelerate these effects on populations.
Second, we investigated whether and how physiological mechanisms can determine the sensitivity of species to ongoing environmental changes. One of our major findings is that individuals of lower quality (i.e. with a low survival probability and poor reproductive performances) had higher stress hormone levels than high-quality individuals. This demonstrates that these low-quality individuals do not cope as well with environmental constraints and environmental changes as high-quality individuals. In addition, we found that low food availability was associated with elevated stress levels and poor reproductive performances in Antarctic seabirds, suggesting that environmental changes (such as profound changes in the trophic web) can be an important threat to some Antarctic seabirds. On the other hand, we also showed that the presence of humans can modify the perception of stress in Antarctic seabirds. Those that breed close to human infrastructures appear to be less sensitive to stress. This suggests that Antarctic seabirds may habituate to human presence and may be able to live around humans after a period of habituation. Importantly, we also demonstrated that all species are not equal when facing environmental changes and stressful events. For instance, through a study conducted at the laboratory, we demonstrated that the sensitivity of species to stressful events was genetically determined. This could potentially explain why some species can adjust better than others to environmental changes. In addition, we demonstrated the role of stress sensitivity in determining the ability of species to cope with global changes by conducting comparative analyses. Therefore, we showed that both stress sensitivity and brain size could explain how individuals cope with novelty (new environmental situations). To conclude, our studies illustrated that stress sensitivity may drive the strategies of individuals and species and, thus, determine their sensitivity to ongoing changes.
Third, the fellow learnt new techniques to study further stress physiology in wild birds. Thus, he brought back from the USA a specific assay to measure corticosterone-binding globulin (CBG) in the plasma of vertebrate species. This measure is crucial because it provides accurate estimates of the impact of environmental changes on the stress levels of individuals and species. In addition, we set up a lab at the Centre dEtudes Biologiques de Chizé to measure telomere length in wild vertebrates. This technique is essential to further understand the effect of climate change on vertebrates because it enables investigation into how environmental stressors and constraints can accelerate ageing and thus impair the biological functions (survival and reproduction) of wild vertebrates. Indeed, we successfully used both of these techniques during this project and, for instance, we showed that stressful environments were associated with an acceleration of telomere shortening and thus with an acceleration of ageing in wild birds.
Finally, we developed eco-physiological theoretical models to try to understand why some individuals would be more likely than others to be affected by environmental changes and extreme environmental conditions. These models raised specific hypotheses that are based on allostasis and will stimulate further studies. We also provided an integrative picture of how stress mechanisms can help to understand how wild birds will cope with global change. Therefore, we proposed review papers to better understand the link between stress, ageing and global change. Our theory is that specific stress sensitivities may be advantageous under some environmental circumstances but not others. The problem is that environmental changes may induce rapid changes in the range of environmental situations that individuals have to cope with. In this context, individuals may need to adjust their stress sensitivity to the new environmental situations in order to cope with a changing environment. We therefore believe that the ability of individuals to show flexible and plastic stress sensitivity is probably crucial to their performances. We also emphasised that stress mechanisms are complex and multiple. Specifically, we showed that is not sufficient to look at corticosterone ("the classic stress hormone") to understand how individuals react to stressors. We explained that other hormones, such as prolactin (the hormone of parental behaviours), are affected by stress and can mediate life-history decisions. We also explained that non-hormonal components can be crucial in studying traits such as behavioural stress response and cardiovascular stress response.
Project impact
By gathering ecological and physiological data, we were able to show that stress mechanisms play an important role in determining the ability of individuals and species to cope with global change. We believe that our studies will help the scientific community to better understand why some individuals/species can better cope with environmental changes than others. Therefore, we think that this project reached its objectives and helped to understand why climate changes affect vertebrates and individuals in contrasting ways; how stress mechanisms can determine the adjustment capacity of vertebrates to environmental changes; and to provide clues to help ecologists and demographers to predict how vertebrate populations will cope with ongoing and future environmental changes.
The aim of the project was to investigate how ongoing climate change could affect vertebrates and, more specifically, birds. This question is crucial because it remains very unclear why some species can adjust to environmental changes whereas others cannot. Indeed, numerous studies have reported population trends (declines, stability and even increases in a few cases) in relation to climate change, but overall our knowledge of the mechanisms that determine the ability of vertebrates to cope with these changes remains poor. As specified in the initial proposal, the project aimed to understand how environmental variables could affect the performances of birds and which physiological mechanisms can play a major role in the ability of birds to cope with ongoing environmental changes.
Project results
During this fellowship, we conducted several studies to reach the project objectives. We combined experimental approaches using captive birds in the USA and field work on Antarctic seabirds in order to better understand what mechanisms are involved in the adjustment of vertebrates to environmental changes. In addition, we developed and used new laboratory techniques in ecology to investigate in detail the physiological mechanisms that may be involved in such adjustments. These developments have been performed in the USA, and the fellow transferred this knowledge to the European institution during the return phase. All these steps were done in collaboration with all the institutions involved in the POLARCLIMSTRESS project (Prof. John C. Wingfield, UC Davis, Prof. Carol M. Vleck, Iowa State University, and Dr Olivier Chastel, CEBC-CNRS). We have disseminated the results from the fellow's studies via publications in scientific journals, conferences and also through some mentoring (undergraduate students).
This project allowed us to improve our understanding of the mechanisms that can link population trends and climate change. First, we first examined in the field how and why some species are affected by climate change. For instance, we showed that warmer temperatures during the breeding season can pose a major threat to reproductive success in some Antarctic seabirds due to unusual snow melting and precipitations. Warm temperatures resulted in flooding of the nests and total breeding failure for many individuals. We also showed that the quality of the nest site can potentially attenuate the negative effects of warm temperatures on breeding performances (especially if parents built their nests in well-drained areas). Importantly, global climate change predicts that major swings in intensity, frequency and duration of storms will increase in the near future, often accompanied by new, record-high temperatures. Therefore, climate change will increase the possibility that flowing water during the breeding season may pose a major threat to the reproductive success of some Antarctic seabirds.
Furthermore, we demonstrated that climate change can also have negative impacts on temperate species. We reported that a prolonged drought reduces bird performances on the wintering ground and that these negative effects can be temporarily attenuated by the quality of the habitat. Our results therefore show that birds from different areas can be affected by climate changes and that habitat degradation may accelerate these effects on populations.
Second, we investigated whether and how physiological mechanisms can determine the sensitivity of species to ongoing environmental changes. One of our major findings is that individuals of lower quality (i.e. with a low survival probability and poor reproductive performances) had higher stress hormone levels than high-quality individuals. This demonstrates that these low-quality individuals do not cope as well with environmental constraints and environmental changes as high-quality individuals. In addition, we found that low food availability was associated with elevated stress levels and poor reproductive performances in Antarctic seabirds, suggesting that environmental changes (such as profound changes in the trophic web) can be an important threat to some Antarctic seabirds. On the other hand, we also showed that the presence of humans can modify the perception of stress in Antarctic seabirds. Those that breed close to human infrastructures appear to be less sensitive to stress. This suggests that Antarctic seabirds may habituate to human presence and may be able to live around humans after a period of habituation. Importantly, we also demonstrated that all species are not equal when facing environmental changes and stressful events. For instance, through a study conducted at the laboratory, we demonstrated that the sensitivity of species to stressful events was genetically determined. This could potentially explain why some species can adjust better than others to environmental changes. In addition, we demonstrated the role of stress sensitivity in determining the ability of species to cope with global changes by conducting comparative analyses. Therefore, we showed that both stress sensitivity and brain size could explain how individuals cope with novelty (new environmental situations). To conclude, our studies illustrated that stress sensitivity may drive the strategies of individuals and species and, thus, determine their sensitivity to ongoing changes.
Third, the fellow learnt new techniques to study further stress physiology in wild birds. Thus, he brought back from the USA a specific assay to measure corticosterone-binding globulin (CBG) in the plasma of vertebrate species. This measure is crucial because it provides accurate estimates of the impact of environmental changes on the stress levels of individuals and species. In addition, we set up a lab at the Centre dEtudes Biologiques de Chizé to measure telomere length in wild vertebrates. This technique is essential to further understand the effect of climate change on vertebrates because it enables investigation into how environmental stressors and constraints can accelerate ageing and thus impair the biological functions (survival and reproduction) of wild vertebrates. Indeed, we successfully used both of these techniques during this project and, for instance, we showed that stressful environments were associated with an acceleration of telomere shortening and thus with an acceleration of ageing in wild birds.
Finally, we developed eco-physiological theoretical models to try to understand why some individuals would be more likely than others to be affected by environmental changes and extreme environmental conditions. These models raised specific hypotheses that are based on allostasis and will stimulate further studies. We also provided an integrative picture of how stress mechanisms can help to understand how wild birds will cope with global change. Therefore, we proposed review papers to better understand the link between stress, ageing and global change. Our theory is that specific stress sensitivities may be advantageous under some environmental circumstances but not others. The problem is that environmental changes may induce rapid changes in the range of environmental situations that individuals have to cope with. In this context, individuals may need to adjust their stress sensitivity to the new environmental situations in order to cope with a changing environment. We therefore believe that the ability of individuals to show flexible and plastic stress sensitivity is probably crucial to their performances. We also emphasised that stress mechanisms are complex and multiple. Specifically, we showed that is not sufficient to look at corticosterone ("the classic stress hormone") to understand how individuals react to stressors. We explained that other hormones, such as prolactin (the hormone of parental behaviours), are affected by stress and can mediate life-history decisions. We also explained that non-hormonal components can be crucial in studying traits such as behavioural stress response and cardiovascular stress response.
Project impact
By gathering ecological and physiological data, we were able to show that stress mechanisms play an important role in determining the ability of individuals and species to cope with global change. We believe that our studies will help the scientific community to better understand why some individuals/species can better cope with environmental changes than others. Therefore, we think that this project reached its objectives and helped to understand why climate changes affect vertebrates and individuals in contrasting ways; how stress mechanisms can determine the adjustment capacity of vertebrates to environmental changes; and to provide clues to help ecologists and demographers to predict how vertebrate populations will cope with ongoing and future environmental changes.