By Bob Berwyn
SUMMIT COUNTY — Not long after biologists with the British Antarctic Survey documented the disappearance of an emperor penguin colony, a new research effort also suggests that climate change may drastically reduce Antarctic habitat for the iconic ice-dwelling birds.
Focusing on a long-studied colony in Terre Adélie, scientists with the Woods Hole Oceanographic Institution concluded that the number of breeding pairs at the colony could drop by 80 percent by the end of the century.
Another recent study by the British Antarctic Survey suggested that emperor penguin populations are much higher, perhaps twice as large, as previously believed. Last November, conservation groups petitioned the U.S. Fish and Wildlife Service to list emperor penguins under the Endangered Species Act.
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 emphasized 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 Adélie, a coastal region of Antarctica where French scientists have observed penguins for more than 50 years.
“Our best projections show roughly 500 to 600 breeding pairs remaining by the year 2100,” says lead author Stéphanie Jenouvrier, a WHOI biologist. “Today, the population size is around 3,000 breeding pairs.”
She said another penguin population on the Dion Islets 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 says.
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 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 the extent of sea ice in the region will change this century, Holland and another co-author, Julienne Stroeve, a sea ice specialist from the National Snow and Ice Data Center, evaluated 20 of the world’s leading computer-based climate models. They selected the five models that most closely reproduced changes in actual Antarctic sea ice cover during the 20th century.
“When a computer simulation performs well in reproducing past climate conditions, that suggests its projections of future climate conditions are more reliable,” Holland says.
The team evaluated simulations from each of the 20 climate models. The simulations were based on a scenario of moderate growth in greenhouse gas emissions during this century. The moderate growth scenario portrays future reliance by society on a combination of greenhouse-gas emitting fossil fuels as well as renewable energy sources.
The simulations showed a decline in sea ice coverage across a large region by Terre Adélie at key times in the penguin breeding cycle, although they differed in the details.
Jenouvrier used the output from the climate models to determine how changes in temperature and sea ice might affect the emperor penguin population at Terre Adélie, studying such details as how the sea ice was likely to vary during breeding season and how it could affect chicks, breeding pairs, and non-breeding adults. She found that if global temperatures continue to rise at their current rate—causing sea ice in the region to shrink—penguin population numbers most likely 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.
The authors say 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.
“We rely on the functioning of those ecosystems,” he says. “We eat fish that come from the Antarctic. We rely on nutrient cycles that involve species in the oceans all over the world. 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.”
Also co-authoring the study were Christophe Barbraud and Henri Weimerskirch of the Centre d’Etudes Biologiques de Chizé, in France, and Mark Serreze of the National Snow and Ice Data Center in the United States.
- Scientists double their estimates of Antarctic emperor penguin populations after careful satellite study (summitcountyvoice.com)
Filed under: biodiversity, climate and weather, endangered species, Environment, global warming Tagged: | Antarctic Peninsula, Antarctica, British Antarctic Survey, climate change, Emperor Penguin, global warming, Woods Hole Oceanographic Institution