Future of emperor penguins on thin ice
By the end of this century, climate change will have cut the worldwide population of emperor penguins to a fraction of what it is today. This finding, which comes out of a study conducted by an international team of researchers including UvA Professor Hal Caswell, underscores the urgency of placing the emperor penguin on the endangered species list. The results of the study have been published in the scientific journal Nature Climate Change.
By linking climate models developed by the Intergovernmental Panel on Climate Change (IPCC), the researchers were able to analyse the impact that changes in sea ice conditions will have on overall trends in emperor penguin (Aptenodytes forsteri) populations. Caswell and his colleagues traced the population dynamics of the 45 emperor penguin colonies on Antarctica for the period up to the end of this century using a sea ice-dependent demographic model integrating local, colony specific circumstances.
Emperor penguins are dependent on sea ice for their survival. When there is too much ice, penguin parents have to travel long distances – sometimes too long – to the ocean to hunt for and bring back food for their chicks. Too little ice, on the other hand, means fewer habitats for krill (small crustaceans), which are the penguins' principal source of food.
Though the projected dynamics are different for each colony, if the concentration of sea ice continues to shrink, all populations will have experienced severe declines by 2100. At least two-thirds of the 45 colonies will have dropped to half their current size. Even more alarming, the overall population will have decreased by at least 19% by this time.
Fifty years of penguin observations
The present research expands on an intensive study on the emperor penguin colony in Terre Adélie (in eastern Antarctica), which has been recording biological measurements every year for the past 50 years. That data has been used to chart the population's growth (and decline), mating, gathering of food and rearing of chicks, as well as tracking individual micro-chipped penguins from one year to the next.
Crucial to conservation
‘Because the criteria for attaining endangered species status are based on overall population dynamics, comprehensive analyses like ours are crucial for species' conservation’, says Caswell. The results of the study will lead to a number of recommendations for the future. For instance, explains Caswell, because the Ross Sea – a deep bay in Antarctica's Southern Ocean – will be the last area affected by climate change, ‘it could offer a haven, provided conservation strategies target this specific region of Antarctica’.
Stéphanie Jenouvrier, Marika Holland, Julienne Stroeve, Mark Serreze, Christophe Barbraud, Henri Weimerskirch, Hal Caswell: Projected continent-wide declines of the emperor penguin under climate change, in: Nature Climate Change (June 2014).
The research was conducted by Hal Caswell, professor of Mathematical Demography and Ecology at the UvA, in collaboration with fellow researchers at Woods Hole Oceanographic Institution (USA), the Centre National de la Recherche Scientifique (France), the National Center for Atmospheric Research (USA) and the Cooperative Institute for Research in Environmental Sciences (USA).