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Modelling the effects of climate change on the population dynamics of an Antarctic seabirds community

Final Activity Report Summary - CLIM POP MOD (Modelling the effects of climate change on the population dynamics of an Antarctic seabirds community)

In the face of climate change, there is a growing demand for accurate assessments and forecasts of its ecological impacts. In the southern ocean, seabirds are long-lived upper trophic-level predators that integrate climate variability over large spatial and temporal scales. Hence, they are useful species to determine the impact of climate change on marine ecosystems. In Antarctica, seabirds are sensitive to change in sea ice conditions because sea ice affects their food resource and / or their habitat. The objectives of the project were to understand and predict the population responses of Antarctic seabirds to present and future climate changes.

The fellow, Dr Jenouvrier, developed novel approaches to analyse and predict the demographic consequences of climate change by linking state-of the art modelling expertise with an impressive data set on Antarctic seabirds in Terre Adélie, Antarctica. Her approach involved international and multi-disciplinary collaborations, with Dr Caswell (Woods Hole Oceanographic Institute, United States), internationally well-known for his expertise on demographic models; with Dr Weimerskirch's group, which is the foremost seabirds ecology research centre (Centre National de la Recherche Scientifique, France), and two internationally recognised climate scientists: Dr Stroeve (National Snow and Ice Data Center, United States) and Dr Holland (National Center of Atmospheric Research, United States).

First, Dr Jenouvrier focused on the effect of sea ice on the population of emperor penguins, through its impact on the vital rates to address three issues:
(1) understanding the mechanisms by which sea ice affects the population in Terre Adélie;
(2) predicting the population response to future change in sea ice; and
(3) comparing the population responses over the entire species range.
Second, she applied her novel and successful modelling approach to two petrel species; the southern fulmar and snow petrel; to (4) compare the population responses to future climate change among species.

Dr Jenouvrier showed that change in sea ice conditions affect dramatically the population of emperor penguins, but not the populations of petrels. Penguins are more sensitive to climate variability than petrels because Emperor Penguins breed almost annually and their adult survival is strongly affected by environmental variations. On the contrary, petrels skip reproduction during unfavourable climate conditions rather than compromising their survival and future opportunities to reproduce.

Dr Jenouvrier projected population responses to future sea ice change by linking demographic models to climate projections by climate models used in the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC). She concluded that if sea ice declines at the rates projected by IPCC models, and continues to influence emperor penguin vital rates as it did in the second half of the 20th century, the population of emperor penguins in Terre Adélie will decline dramatically by 2100. This population responses contrast with the results she obtained for the two petrels species, which do not show strong decline by 2100.

Finally, Dr Jenouvrier projected the effect of future sea ice change on populations of emperor penguins over their entire distribution range. Almost all the emperor penguin colonies are projected to decline dramatically. The lowest projected probabilities of quasi-extinction (i.e. decline>95 %) are in the Ross Sea and the east coast of the Antarctic Peninsula. Thus, these places may be the last sanctuary for emperor penguin in the near future, although they will not sustain populations for a long time.