If global temperatures continue to rise, Emperor penguins may eventually disappear from their East Antarctic home, according to a new study by Woods Hole Oceanographic Institution (WHOI) researchers.
"Over the last century, we have already observed the disappearance of the Dion Islets penguin colony, close to the West Antarctic Peninsula," says WHOI biologist Stephanie Jenouvrier.
"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."
The team believes that the decline of those penguins may be connected to a simultaneous loss of 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.
"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," says Jenouvrier.
Disappearing sea ice may also affect the penguins' food source. They live mainly on fish, squid, and krill, which in turn feeds on zooplankton and phytoplankton, tiny organisms that grow on the underside of the ice. If the ice goes, so too will the plankton, causing a ripple effect through the food web.
To reach their conclusions, 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 results indicated that if greenhouse gas emissions continue to rise at levels similar to today, 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.
"Our best projections show roughly 500 to 600 breeding pairs remaining by the year 2100. Today, the population size is around 3,000 breeding pairs," says Jenouvrier.