June 20th, 2012 by James Ayre
The Emperor penguin, Antarctica’s iconic, nearly 4-foot-tall sea bird, is likely to see its populations collapse as warming and ice loss in Antarctica accelerates. According to a new study from the Woods Hole Oceanographic Institute (WHOI), the Emperor penguins living in Terre Adélie, in East Antarctica, will eventually disappear if the presently occurring warming and loss of ice continues along with increasing rates of sea level rise. Which, according to nearly all research done on the matter, is likely to not only continue, but rapidly accelerate.
“Over the last century, we have already observed the disappearance of the Dion Islets penguin colony, close to the West Antarctic Peninsula,” says Stephanie Jenouvrier, WHOI biologist and lead author of the new study. “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 study authors think that the decline of those penguins is likely connected to the simultaneous decline in Antarctic sea ice in that region.
Emperor penguins are dependent on sea ice — they breed and raise their young almost exclusively on it. With the loss of that ice 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,” Jenouvrier says.
The disappearance of sea ice also affects the penguins’ food source. “The birds feed primarily on fish, squid, and krill, a shrimp-like animal, which in turn feeds on zooplankton and phytoplankton, tiny organisms that grow on the underside of the ice.”
With the ice loss, there will also be a loss of plankton, causing damage all the way up through the food web, potentially starving the different species that penguins rely on as prey.
To project how the penguin populations will do in the future, the researchers used data from many 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.”
Mixing this long-term population data with information on climate is the key to the study, says Hal Caswell, a WHOI senior mathematical biologist and collaborator on the paper.
“If you want to study the effects of climate on a particular species, there are three pieces that you have to put together,” he says. “The first is a description of the entire life cycle of the organism, and how individuals move through that life cycle. The second piece is how the cycle is affected by climate variables. And the crucial third piece is a prediction of what those variables may look like in the future, which involves collaboration with climate scientists.”
A researcher from the National Center for Atmospheric Research, Marika Holland, is one of those climate scientists. Specializing in the study of the relationship between sea ice and global climate, she helped the team identify the right climate models for use in this study.
Together with another sea ice specialist from the National Snow and Ice Data Center, Julienne Stroeve, Holland ultimately recommended five distinct models.
“We picked the models based on how well they calculated the sea ice cover for the 20th century,” she says. “If a model predicted an outcome that matched what was actually observed, we felt it was likely that its projections of sea ice change in the future could be trusted.”
The output from these various different climate models was used to determine how changes in temperature and sea ice might affect the Emperor penguin population at Terre Adélie. Finding that if greenhouse gas emissions continue to rise at levels similar to today — causing temperatures to rise and Antarctic sea ice to shrink — penguin populations will slowly diminish until around 2040, after that they will then begin a steep decline because of the loss of a minimum usable ice coverage.
“Our best projections show roughly 500 to 600 breeding pairs remaining by the year 2100. Today, the population size is around 3000 breeding pairs,” says Jenouvrier.
The rising temperature in the Antarctic and its associated effects isn’t just a penguin problem, says Caswell. As the sea ice coverage continues to become more and more limited, the resulting changes in the Antarctic marine environment will affect every other species, including humans.
“We rely on the functioning of those ecosystems. We eat fish that come from the Antarctic. We rely on nutrient cycles that involve species in the oceans all over the world,” he says.
“Understanding the effects of climate change on predators at the top of marine food chains — like Emperor penguins — is in our best interest, because it helps us understand ecosystems that provide important services to us.”
Source: Woods Hole Oceanographic Institute
Image Credits: Stephanie Jenouvrier, Woods Hole Oceanographic Institution
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