Melting sea ice trouble for Emperor penguins

Grim news for Emperor penguins. If global temperatures continue to rise, and sea ice continues melting, the Emperor penguins in Terre Adélie, East Antarctica may eventually disappear. That’s according to a study in the June 20, 2012 edition of the journal Global Change Biology.

Stephanie Jenouvrier is a biologist at the Woods Hole Oceanographic Institution (WHOI) and lead author of the new study. She said:

Over the last century, we have already observed the disappearance of the Dion Islets penguin colony, close to the West Antarctic Peninsula. In 1948 and the 1970s, scientists recorded more than 150 breeding pairs there. By 1999, the population was down to just 20 pairs, and in 2009, it had vanished entirely.

Like in Terre Adélie, Jenouvrier thinks the decline of those penguins might be connected to a simultaneous decline in Antarctic sea ice due to warming temperatures in the region.

Unlike other sea birds, Emperor penguins breed and raise their young almost exclusively on sea ice. If that ice breaks up and disappears early in the breeding season, massive breeding failure may occur. Jenouvrier said:

As it is, there’s a huge mortality rate just at the breeding stages, because only 50 percent of chicks survive to the end of the breeding season, and then only half of those fledglings survive until the next year.

Disappearing sea ice may also affect the penguins’ food source. The birds feed primarily on fish, squid, and krill, a shrimplike animal, which in turn feeds on zooplankton and phytoplankton, tiny organisms that grow on the underside of the ice. If the ice goes, Jenouvrier says, so too will the plankton, causing a ripple effect through the food web that may starve the various species that penguins rely on as prey.

To project how penguin populations may fare in the future, Jenouvrier’s team used data from several different sources, including climate models, sea ice forecasts, and a demographic model that Jenouvrier created of the Emperor penguin population at Terre Adélie, a coastal region of Antarctica where French scientists have conducted penguin observations for more than 50 years.

The researchers used various climate models to determine how changes in temperature and sea ice might affect the Emperor penguin population at Terre Adélie. They found that if greenhouse gas emissions continue to rise at levels similar to today — causing temperatures to rise and Antarctic sea ice to shrink — penguin population numbers will diminish slowly until about 2040, after which they would decline at a much steeper rate as sea ice coverage drops below a usable threshold. Jenouvier said:

Our best projections show roughly 500 to 600 breeding pairs remaining by the year 2100. Today, the population size is around 3000 breeding pairs.

Bottom line: If global temperatures continue to rise, and sea ice continues melting, the Emperor penguins in Terre Adélie, East Antarctica may eventually disappear. That’s according to a study in the June 20, 2012 edition of the journal Global Change Biology.

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