The fall of emperor penguins

Disappearing sea ice could result in a significant decline in the Antarctic population of emperor penguins (Aptenodytes forsteri) by the end of the 21st century.

Although dynamics differ in different colonies, all 45 known emperor penguin colonies in Antarctica are expected to be in decline by 2100, with two-thirds of colonies projected to shrink to less than half of their present population.

The findings are based on projected changes in Antarctic sea-ice concentration under climate change and, according to the researchers, justify protecting emperor penguins under the Endangered Species Act. Like the polar bear, which is now protected because of melting Arctic sea ice, the main threat to emperor penguins’ survival is loss of sea ice.

Emperor penguins breed and raise their offspring almost exclusively on sea ice. Changes in sea ice cover impact the Antarctic food web through key organisms, such as krill. These tiny crustaceans are the emperor penguins’ main food source. A loss of sea ice reduces the supply of krill, whereas too much sea ice requires adults to travel further to find food, reducing chick feeding frequency.

Stéphanie Jenouvrier from Woods Hole Oceanographic Institution in the US and colleagues modelled population trends for the 45 known emperor penguin colonies, taking account of sea-ice conditions projected by a range of climate models.

Only one emperor penguin population has been intensively studied: the colony in Terre Adélie, in East Antarctica. A detailed analysis of the effects of climate change on this colony, which has been studied for five decades, projected a pronounced decline by the end of this century.

The researchers found that although year-to-year colony population growth rates are mostly positive until 2040, all colonies will begin to experience negative growth by 2080.

The researchers said the findings called for urgent measures to help the penguins survive - such as legal protections under the Endangered Species Act and the creation of marine reserves off Antarctica.

“Implementing a marine protected area in the Ross Sea could help buy time to avoid extinction and to put in place needed conservation and greenhouse gas mitigation strategies,” Jenouvrier said in a statement.

A marine reserve would potentially reduce pressure on krill, and improve penguin survival, by closing large areas of the Southern Ocean to fishing.

“We propose that the emperor penguin is fully deserving of endangered status due to climate change, and can act as an iconic example of a new global conservation paradigm for species threatened by future climate change,” the authors stated.

The study was reported in Nature Climate Change.

Photo credit: Credit: Stephanie Jenouvrier.