Antarctic sea ice loss threatening emperor penguins

Washington - Loss of Antarctic sea ice due to climate change may cause a significant decline in the population of emperor penguins this century, a new study has predicted.

The study, led by the Woods Hole Oceanographic Institution (WHOI), with researchers from the National Center for Atmospheric Research (NCAR) and other organizations, focuses on a much-observed colony of emperor penguins in Terre Adelie, Antarctica.

They team concluded that the number of breeding pairs may fall by about 80 percent by 2100.

“The projected decreases in sea ice may fundamentally alter the Antarctic environment in ways that threaten this population of penguins,” said NCAR scientist Marika Holland, a co-author of the study.

The study uses a set of sophistical computer simulations of climate as well as a statistical model of penguin demographics. Building on previous work, it examines how the sea ice may vary at key times during the year such as during egg laying, incubation, rearing chicks, and non- breeding season, as well as the potential influence of sea ice concentrations on males and females.

The researchers stressed that their projections contain large uncertainties, because of the difficulties in projecting both climate change and the response of penguins. However, almost all of their computer simulations pointed to a significant decline in the colony at Terre Adelie, a coastal region of Antarctica where French scientists have conducted penguin observations for more than 50 years.

“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,” said lead author Stephanie Jenouvrier, a WHOI biologist.

She noted that another penguin population, the Dion Islets penguin colony close to the West Antarctic Peninsula, has disappeared, possibly because of a decline in Antarctic sea ice.

The new research represents a major collaboration between biologists and climate scientists to assess the potential impacts of climate change on a much-studied species.

At nearly four feet tall, emperors are the largest species of penguin. They are vulnerable to changes in sea ice, where they breed and raise their young almost exclusively. If that ice breaks up and disappears early in the breeding season, massive breeding failure may occur, Jenouvrier explained.

Disappearing sea ice may also affect the penguins’ food sources. They feed primarily on fish, squid, and krill, a shrimplike animal that feeds on zooplankton and phytoplankton that grow on the underside of ice.

If the ice goes, Jenouvrier said, 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.

The researchers noted that more research is needed to determine whether emperor penguins may be able to adapt to changing conditions or disperse to regions where the sea ice is more habitable.

Rising temperature in the Antarctic isn’t just a penguin problem, according to Hal Caswell, a senior mathematical biologist at WHOI and collaborator on the study. As sea ice coverage continues to shrink, the resulting changes in the Antarctic marine environment will affect other species, and may affect humans as well.

The study was published this week in the journal Global Change Biology.