For millions of years, fluctuating climates have impacted Adélie penguins, which breed on ice-free, rocky ground.
Colder climates and expanding glaciers led penguins to abandon ice-covered breeding habitats. Warming climates and melting glaciers meant more breeding territory for these penguins, one of only two true Antarctic penguin species. (Emperor penguins are the other.)
But warming may have reached a tipping point — and the Adélie penguin population could be decimated.
That’s according to a study published this week in the journal Scientific Reports, which estimates that Adélie colonies could decline by as much as 60 percent by the end of the century.
“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,” the paper’s lead author, University of Delaware researcher Megan Cimino, said in a statement.
These penguins breed on the entire Antarctic continent.
Other penguins breed on the northern tip of the Antarctic Peninsula, which scientists warn is quickly warming.
The Adélie penguin is already undergoing population declines on the West Antarctic Peninsula, one of the fastest-warming places on the planet.
But elsewhere on the continent, in places where the climate has remained stable or even cooled, the penguin population has been stable or even increased.
While in the past, “Adélie penguin populations were positively affected by warming and negatively affected by cooling,” the authors write, this study suggests “that in many regions of Antarctica climate warming has tipped past peak suitability so that further warming is no longer beneficial to Adélie penguins.”
In particular, climate change could decrease the quality and availability of nesting grounds and food.
Adélie penguins build their nests with pebbles on terrain free of ice and snow. Eggs and chicks need to be kept dry and out of water.
Warming climates could bring more rain, or prematurely melting snow or ice, meaning more wet terrain.
“For penguins who lay their eggs on the ground,” Cimino told National Geographic, “rain and puddles are bad because eggs can’t survive when they’re lying in a pool of water. Chicks that don’t have waterproof feathers can become wet and die from hypothermia.”
Climate change could also lead to a decrease in krill, a major food source for Adélie penguins, and affect the species.
There is some hope: The study’s projections suggest there could be areas of relatively unaltered climate on the Antarctic continent after 2099, providing a refuge to penguins and buffering a species-wide decline.
In particular, the Cape Adare region of the Ross Sea, thought to have once been a climate refuge in the past, could become one in the future as well.
The study’s model projects that one-third of the current Adélie colonies (or 20 percent of the entire population) could decline by 2060.
And 60 percent of colonies could decline by 2099.
To create the model to measure climate change’s impact on Adélie penguin colonies, the research team used satellite imagery, global climate change projections and field surveys.
Satellite observations between 1981 and 2010 provided sea surface temperature, sea ice and bare rock locations. The researchers used global estimates of the penguin’s breeding locations — where they are and aren’t — from on-the-ground penguin counts and high-resolution satellite imagery.
“One of the key advances over the last decade is our ability to find penguin colonies from space and, nearly as important, to determine which areas of Antarctica do not support penguin colonies,” co-author Heather J. Lynch, an assistant professor at Stony Brook University’s Ecology and Evolution Department, said in a statement. “Having both true presence and absence across a species’ global range is unique to this system, and opens up new avenues for modeling habitat suitability.”