We’ve all heard the dire predictions about the world’s polar bears: according to the U.S. Geological Survey, two-thirds of them could disappear by 2060, even under moderate projections for shrinking summer sea ice caused by greenhouse gases in the atmosphere. But what’s happening at the other pole—although not as often reported in the media—with its most iconic animals, penguins, could be just as startling.
At first glance, two recent studies that were published in January regarding the world’s penguin populations seem to be at odds: while one shows that Magellanic penguins are suffering due to climate change, another suggests that Adélie penguins may be adapting just fine.
Or are they?
In the Falkland Islands
For 27 years, a team from the University of Washington and the Wildlife Conservation Society studied a multitude of factors responsible for chick mortality in the world’s largest colony of Magellanic penguins, a species that inhabits coastal regions of Argentina, Chile and the Falkland Islands. Between 1983 and 2010, researchers collected data on nearly 3,500 chicks. While starvation and predation caused the majority of deaths in most of those years, heavy storms and extreme heat have taken an increasing toll over time. What stands out is that weather never used to be an important mortality factor for these birds—and now it is.
The chicks are most vulnerable between nine and 40 days after hatching, when they are too large to seek shelter under their parents’ bodies but have not yet developed waterproof plumage. Baby penguins are more likely now than three decades ago to catch hypothermia during storms or succumb to excessive heat. Since 1987, Magellanic penguins have lost 20 percent of their population.
Meanwhile, farther south in the Ross Sea
In another part of Antarctica—farther south—however, the story seems to be different. The results of a second study published on January 29, 2014, in PLOS One suggests that lower summer sea ice concentrations than currently observed would benefit the foraging performance of Adélie penguins in their southernmost breeding area in the Ross Sea.
The team in this research project studied Adélie penguins over a 13-year period and found that the birds can mostly adapt their foraging behavior to varying amounts of seasonal sea-ice coverage. Since scientists predict that sea-ice coverage will shift dramatically in the coming decades—with summer coverage shrinking as oceans warm—that’s very good news.
Will penguin colonies continue to fail as the climate warms? ©Candice Gaukel AndrewsBut Adélie penguins have a Goldilocks-like relationship with sea ice: it has to be “just right.” For the birds, sea ice is essential for finding food (it hosts prey species, such as krill, on its underside), it provides a site to rest and molt, and it eases migration. But too much sea ice, or if it is too thickly packed close to shore—especially during chick-rearing season—can be bad. Then, penguin parents have to travel farther to the ice’s edge to fi