The biggest threat to emperor penguins may not be leopard seals or even killer whales, but a much larger predator: global warming.
Climate change, which is quickly melting the sea ice this species depends on for survival, could cause dramatic drops in the number of emperor penguins across Antarctica by the end of the century, a new study finds. Specifically, more than two-thirds of Antarctica's emperor penguin colonies will decline by more than 50 percent by the end of the century under future climate change scenarios.
The researchers, from France, the Netherlands and the United States, are pushing to have this iconic species listed as endangered before its numbers hit critical lows. Doing so, the researchers said, may establish "a new global conservation paradigm for species threatened by future climate change." [See Photos of Antarctica's Amazing Penguin Chicks]
The research, detailed yesterday (June 29) in the journal Climate Change, is based in part on a 50-year intensive study — supported by the French Polar Institute (IPEV) and Zone Atelier Antarctique (LTER France) — of an emperor penguin colony in Terre Adélie, East Antarctica. Researchers have been closely monitoring the Terre Adélie population each year, collecting biological measurements of the penguins there and charting the population's growth and decline.
"Long-term studies like this are invaluable for measuring the response of survival and breeding to changes in sea ice," said Hal Caswell, a scientist with the Woods Hole Oceanographic Institution (WHOI) in Massachusetts and the University of Amsterdam. "They provide our understanding of the role sea ice plays in the emperor penguin's life cycle."
Emperor penguins breed and raise their offspring almost exclusively on sea ice. And changes in sea ice concentration (SIC), or the relative area of water covered by sea ice, affect not only penguins, but also the entire Antarctic food web, down to the smallest of species, the researchers noted.
"The role of sea ice is complicated," said Stephanie Jenouvrier, a biologist with the WHOI, in a statement. "Too much ice requires longer trips for penguin parents to travel to the ocean to hunt and bring back food for their chicks. But too little ice reduces the habitat for krill, a critical food source for emperor penguins. Our models take into account both the effects of too much and too little sea ice in the colony area."
Both Jenouvrier and Caswell have previously studied how changes in the concentration of sea ice might affect emperor penguin populations over the next several decades. In 2012, the two scientists and their team published a study in the journal Global Change Biology, which found that the Terre Adélie penguin population could decline by 80 percent by the end of this century. [Happy Feet: A Gallery of Pudgy Penguins]
For their newest study, the researchers expanded on this previous work, using the established population models from Terre Adélie to project how all 45 of Antarctica's known emperor penguin colonies would respond to future climate change. The projections included in the study are based on the current sea ice concentration and anticipated ones at each location.