Climate has influenced the distribution patterns of Adélie penguins across Antarctica for millions of years. The geologic record tells us 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.

Adélie penguins are one of three true Antarctic penguins as they breed along the rocky coastline of Antarctica. Approximately 2.5 million breeding pairs are estimated for the entire continent. Picture: Michael Wenger
Adélie penguins are one of three true Antarctic penguins as they breed along the rocky coastline of Antarctica. Approximately 2.5 million breeding pairs are estimated for the entire continent. Picture: Michael Wenger

The Adélie penguin is a species that breeds around the entire Antarctic continent. The species is experiencing population declines along the West Antarctic Peninsula (WAP), which is one of the most rapidly warming places on Earth, while Adélie populations in other areas around the continent where the climate is stable or even cooling remain steady or increasing. In a paper published today 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.

The researchers’ objective was to understand the effects of climate change on Antarctic Adélie penguin colonies. The study builds on previously published work and used satellite data and global climate model projections to understand current and future population trends on a continental scale. “Our study used massive amounts of data to run habitat suitability models. When we combined this data with satellite information and future climate projections on sea surface temperature and sea ice, we can look at past and future changes in Adélie penguin habitat suitability,” Cimino said.

Many colonies along the western Antarctic Peninsula have experienced a decrease in population size due to the warming of the waters which leads to ice loss and thus less krill, the key to the Adélies survival. Picture: Michael Wenger
Many colonies along the western Antarctic Peninsula have experienced a decrease in population size due to the warming of the waters which leads to ice loss and thus less krill, the key to the Adélies survival. Picture: Michael Wenger

According to Cimino, the southern WAP, associated islands and northern WAP regions, which are already experiencing population declines, are projected to experience the greatest frequency of novel climate this century due to warm SST. This suggests that warm sea surface temperatures may cause a decrease in the suitability of chick-rearing habitats at northerly latitudes. “Within this region we saw the most novel climate years compared to the rest of the continent. This means the most years with warmer than normal sea surface temperature. These two things seem to be happening in the WAP at a higher rate than in other areas during the same time period,” Cimino said.

By contrast, the study also suggests several refugia — areas of relatively unaltered climate — may exist in continental Antarctica beyond 2099, which would buffer a species-wide decline. Understanding how these refugia operate is critical to understanding the future of this species. “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. 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,” Cimino said. The researchers reported that climate change impacts on penguins in the Antarctic will likely be highly site specific based on regional climate trends, and that a southward contraction in the range of Adélie penguins is likely over the next century. “Studies like this are important because they focus our attention on areas where a species is most vulnerable to change,” concluded Cimino. “The results can be used for management; they can have implications for other species that live in the area and for other ecosystem processes.”

The colony of Adélie penguins near Borchgrevink’s hut at Cape Adare is one of the largest penguin colonies in Antarctica. Maybe here lies the key to the survival of the species in the future. Picture: Michael Wenger
The colony of Adélie penguins near Borchgrevink’s hut at Cape Adare is one of the largest penguin colonies in Antarctica. Maybe here lies the key to the survival of the species in the future. Picture: Michael Wenger

Source: Karen B. Roberts, University of Delaware