Adélie penguins (Pygoscelis adeliae) have occupied Antarctica and its surrounding seas since as long ago as 45,000 years. Throughout this time they have endured the effects of alternate cooling and warming, with colonies being abandoned during periods of glacial expansion, and then reoccupied during periods of glacial retreat. Over geological time, therefore, Adélie penguins would appear to benefit from a certain amount of climatic warming.

Now, however, researchers at the University of Delaware suggest climate warming in some parts of Antarctica has reached a tipping point beyond which further warming may spell disaster for the penguins. In a paper published last week in Scientific Reports, Megan Cimino and colleagues combine climate change projections with data on penguin distribution and abundance to predict the fate of Adélie penguin colonies over the coming century. Sadly, their predictions do not make for happy reading.

Cimino’s models suggest that by 2099 around 60% of Adélie penguin colonies will be in population decline. Given that these colonies contain around half of the world’s Adélie penguin population, that spells bad news for these aquatic predators.

Using detailed satellite imagery and data on sea surface temperature and sea ice concentration, the researchers were able to map the frequency of novel climate and associated changes in the suitability of chick-rearing habitat, both historically and into the future. They found that novel climate – that outside the range seen historically – was more frequent at those colonies with decreasing populations. More often than not, the novel climate found at these declining colonies was a result of warmer sea surface temperatures.

Although Cimino and colleagues cannot yet provide a mechanistic link between novel climates and declining colonies, they speculate that warmer sea surface temperatures could negatively impact the availability of favourite penguin foods such as krill and fish, or the quality of nesting habitat. As Cimino explains, “for penguins who lay their eggs on the ground…rain and puddles are bad because eggs can’t survive when they’re lying in a pool of water.”

Adélie penguins are named for the place they were first discovered: Adélie Land, a thin sliver of territory in Antarctica. However, far from being restricted to Adélie land, Adélie penguins are distributed throughout Antarctica and are in turn exposed to the varying extents of climate change across the Antarctic continent. This variability may offer a glimmer of hope for the imperilled penguins.

Although the West Antarctic Peninsula is on a particularly fast warming trajectory, and is consequently projected to see a substantial decrease in the suitability of chick-rearing habitats, the situation in the Ross and Amundsen Seas may be much more favourable. “The Cape Adare region of the Ross Sea is home to the earliest known penguin occupation and has the largest known Adélie penguin rookery in the world,” said Cimino.” Though the climate there is expected to warm a bit, it looks like it could be a refugia in the future, and if you look back over geologic time it was likely a refuge in the past.”

Undoubtedly, the future of the Adélie penguin is under threat. However, Cimino and colleagues hope that studies like theirs, which identify the differing impacts of climate change across a species range, will help practitioners to prioritise conservation efforts wisely.

references

Cimino, M. A., Lynch, H. J., Saba, V. S. & Oliver, M. J. (2016). Projected asymmetric response of Adélie penguins to Antarctic climate change. Scientific Reports, 6, 28785. doi:10.1038/srep28785

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