Climate has influenced the distribution patterns of Adélie penguins across Antarctica for millions of years. The geologic record shows that as glaciers expanded and covered Adélie breeding habitats with ice, penguin colonies were abandoned. When the glaciers melted during warming periods, this warming positively affected the Adélie penguins, allowing them to return to their rocky breeding grounds.

But now, University of Delaware scientists and colleagues report that this beneficial warming may have reached its tipping point.

In a paper published today (June 29) in Scientific Reports, the researchers project that approximately 30 percent of current Adélie colonies may be in decline by 2060 and approximately 60 percent may be in decline by 2099.

"It is only in recent decades that we know Adélie penguins population declines are associated with warming, which suggests that many regions of Antarctica have warmed too much and that further warming is no longer positive for the species," said the paper's lead author Megan Cimino, who earned her doctoral degree at UD in May.

Co-authors on the work include Matthew Oliver, principal investigator on the project and Patricia & Charles Robertson Professor of Marine Science & Policy in UD's College of Earth, Ocean, and Environment; Heather J. Lynch, assistant professor in the Department of Ecology and Evolution at Stony Brook University; and Vincent S. Saba, a research fishery biologist with the National Oceanic and Atmospheric Administration's National Marine Fisheries Service.