A recent study on emperor penguins at Terre Adélie provides more evidence that global warming will be bad news for this species over the long term.

To provide projections of the penguins’ possible fate, Woods Hole Oceanographic Institution biologist Stéphanie Jenouvrier and her colleagues linked a mathematical models of emperor population dynamics to scenarios of possible future changes in sea ice calculated using IPCC climate models.

Stephanie Jenourvrier with emperor penguin chick
WHOI biologist Stephanie Jenouvrier readies an Emperor penguin chick for tagging during fieldwork in December 2011 in Terre Adélie. The research team (Centre d’Etudes Biologiques de Chizé and Institut Pluridisciplinaire Hubert Curien) used Passive Inductive Transponder (PIT) Tag technology. PIT technology helps identify the birds and track demographic data, such as whether they return to the colony to breed and raise chicks.

“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, lead author of the new study, which was made public in June. The researchers also found a chance that the population at the colony could decline even further, by 90%, and even eventually disappear. The most optimistic picture would be a population increase until about 2080, followed by a sharp decrease during roughly the last decade of this century.

According to the authors,  “overall, the ensemble of models predicts that population declines are far more likely than population increases. We conclude that climate change is a significant risk for the emperor penguin.”

“Over the last century, we have already observed the disappearance of the Dion Islets penguin colony, close to the West Antarctic Peninsula,” says 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.”

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, says Jenouvrier. “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,” she says.

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.

Sources:
Woods Hole Oceanographic Institute media release
Stephanie Jenouvrier’s pages at Woods Hole Oceanographic Institute
Effects of climate change on an emperor penguin population: analysis of coupled demographic and climate models

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