Climate change may be poised to claim its first Hollywood celebrities. Shrinking sea ice could wipe out the tuxedoed cast of March of the Penguins--or their descendents--by the end of the century, researchers report online today in the Proceedings of the National Academy of Sciences. Other emperor penguins that live farther south may fare better.
Emperor penguins--the world's largest at over a meter tall--are completely dependent on sea ice. They breed on it, and they eat fish that ultimately rely on the plankton that grows under it. As the globe warms, sea ice cover is declining in the Arctic; that's why polar bears, which hunt from the ice, are in trouble. The picture in Antarctica is less clear.
To gauge the impact on emperor penguins, ecologist Stéphanie Jenouvrier of the Woods Hole Oceanographic Institution in Massachusetts focused on a population in Pointe Géologie, Antarctica. The penguins there spend the winter on ice close to Dumont d'Urville, the main French base in Antarctica, and records on them stretch back to the 1960s. They're also notable as the stars of the 2005 documentary, March of the Penguins. Jenouvrier and her colleagues used the long-term data set to create a model describing the birds' life histories. They plugged in figures such as the age of the penguins when they start breeding and how likely the chicks are to survive. These details can reveal a more accurate picture of how a population will respond to a change in the environment. The team then linked this model to another set of models predicting how often the penguins will experience a major drop in sea ice as the climate changes between now and 2100.
Given the increasing frequency of 10% to 15% dips in sea ice forecast over the next century by the climate models the team used, Jenouvrier and colleagues predict that the number of Pointe Géologie penguins will plummet from 3000 to 400 breeding pairs. Finding a new home isn't an option, says Jenouvrier, because the penguins have to stick to the coast--and in that part of the continent, it's solid land to the south.
"Their conclusions for the Pointe Géologie colony are reasonable, in fact, optimistic considering the state of our present world," says penguin expert Gerald Kooyman of the Scripps Institution of Oceanography in San Diego, California. Still, penguin lovers shouldn't despair just yet. Kooyman notes that many of the 400,000 or so emperor penguins in Antarctica live farther south, where it's colder and sea ice may behave differently. "Are emperor penguins as a species in trouble?" he asks. "I don't think so."
And sea ice geophysicist Stephen Ackley of the University of Texas, San Antonio, says that even the Pointe Géologie penguins may be okay, as he doesn't think the climate models are accurate enough to predict what sea ice will do. According to the models, "we should have already seen a decline of sea ice in the 1990s," he says. Instead, "we're seeing an increase. ... I have to be skeptical about how well they can predict the future."