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Emperor penguins could be well on their way to extinction if climate change affects sea ice around Antarctica as expected, a new study reveals. Data gathered at a penguin rookery in Terre Adélie, Antarctica, between 1962 and 2005 indicate that the breeding success of emperor penguins, the tallest living penguin species, is strongly linked to the extent of winter sea ice in the region, says Hal Caswell, a mathematical ecologist at the Woods Hole Oceanographic Institution in Massachusetts.

For example, when the extent of winter sea ice off Terre Adélie dropped an average of about 11 percent for several consecutive years, penguin populations there declined by 50 percent. But when sea ice was extensive, populations of krill — the tiny marine crustaceans that feed the fish that, in turn, feed the emperors — are high, he and his colleagues note online January 26 in Proceedings of the National Academy of Sciences.

In the 1960s, about 6,000 breeding pairs of emperor penguins lived in Terre Adélie, Caswell notes. Combining data on population trends with sea-ice projections developed by the Intergovernmental Panel on Climate Change, the researchers estimate that the rookery will host only 400 breeding pairs by the end of this century. — Sid Perkins