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July 13, 2009

Climate Change Likely to Devastate Emperor Penguin Populations in Antarctica


Survival of species could be threatened

You might call them the "poster children" of Antarctica. Penguins have long topped the charts as the iconic animal of the frozen continent.

But now, a new study indicates melting sea ice, caused by climate change, may soon wreak havoc on one colony of emperor penguins--and that could spell doom for a large swath of the entire species.

"We show that if the sea ice shrinks, as projected by climate models, the population will decrease--we show a dramatic decrease--by the end of the century," said population ecologist Stephanie Jenouvrier. "The population will decline from about 3,000 breeding pairs to date to 400 breeding pairs by the end of the century."

Jenouvrier has been to Antarctica twice to study penguins around the French research station in Terre Adelie. One colony of emperor penguins in that area is perhaps the best documented on the continent. French scientists have been monitoring the colony since the 1960s.

A long-term proposition

"In order to analyze the dynamics of this population and see how the population relates to changes in sea ice, we need a very long-term, consistent monitoring of the population, to give us the data that we need," said biologist Hal Caswell with the Woods Hole Oceanographic Institute.

In a study funded in part by the National Science Foundation (NSF), biologist Caswell and Jenouvrier teamed up to model how the Terre Adelie emperor penguin population will likely respond to melting sea ice associated with climate change.

"Their breeding colonies are on sea ice. And they rely on that ice being stable throughout the period while they are laying their eggs and rearing their chicks," said Caswell. "In addition, and equally important, the sea ice provides the base of the food chain that they rely on."

Impact of earlier warming

As it turns out, there is evidence in the historical record that hints at how emperor penguins respond to decreasing levels of sea ice.

"In the 1970s, there was a period of about eight or nine years when sea ice declined by about 10 or 11 percent," said Caswell. "During that period, the emperor penguin population there crashed by about half--it went from about 6,000 breeding pairs down to about 3,000 breeding pairs."

By the early 1980s, colder temperatures returned and the population stabilized. But the episode serves as a worrisome harbinger of things to come. Scientists predict that unless we start scaling back the amount of carbon dioxide and other greenhouse gases that we are pumping into the atmosphere, temperatures could rise by 2 to more than 11 degrees Fahrenheit over the next century. The resulting breakup of sea ice will nearly wipe out the colony at Terre Adelie.

"It's a decline higher than 90 percent decrease, so it's a very high decline that puts the population at a higher risk of extinction," remarked Jenouvrier, adding that penguin colonies in other parts of Antarctica will likely suffer, too. "We need more research to make a projection at the species level, but it's true that the population will have a severe decline."

Chances for survival

As Antarctica warms, sea ice may be more stable in other parts of the continent, like the Ross Sea.

"Some areas of Antarctica, the Ross Sea in particular, are more protected and look as if they're areas where sea ice is likely to persist longer and be in better condition. And, in those areas would presumably be places where the emperor penguins would have a better chance of long term survival," said Caswell.

Is it too late to save the emperor penguin?

Caswell says coordinated global action is needed, and soon.

"It's definitely true that trying to make changes in something the size of the global climate system is a very slow process. It is like trying to change the direction of something like an aircraft carrier. I don't really know the answer to the question of whether it's too late for the emperor penguin, but it certainly is time to start trying to do something about it. The situation won't get any better the longer that we delay in taking action."

Miles O'Brien, Science Nation Correspondent
Kate Tobin, Science Nation Producer


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