Three-quarters of Big Antarctic Penguin Colonies to Disappear?

Ker Than, National Geographic News 1 Dec 08;

Up to 75 percent of major Antarctic penguin colonies may disappear if climate change continues to heat up the continent, according to a recent report.

A global temperature increase of 3.6 Fahrenheit (2 degrees Celsius) above pre-industrial levels will result in widespread changes to sea ice that the birds depend on for survival.

The temperature increase will, in any scenario, lead to a major reshuffling of colonies of emperor and Adélie penguins—the two penguin species that rely on ice for hunting and breeding.

In addition, there could be marked habitat loss of these iconic birds, said the report commissioned by the conservation group WWF.

The penguins' range is already shrinking, said David Ainley, a penguin expert with H.T. Harvey & Associates of San Jose, California, who co-authored the report.

Up to 50 percent of emperor colonies and 75 percent of Adélie colonies could be affected, the researchers said.

Antarctica currently has about 40 emperor colonies and 160 Adélie colonies, with each population containing thousands of birds.

Tightening Noose

Many scientists consider 3.6 degrees Fahrenheit (2 degrees Celsius) to be the minimum temperature increase necessary to trigger catastrophic climate change.

"If you go beyond 2 degrees it really gets scary," Ainley said.

According to the latest report by the U.N.'s Intergovernmental Panel on Climate Change (IPCC), released in February 2007, that threshold could be reached in as little as 40 years.

The WWF report combines results from four IPCC climate models to predict changes that will occur in oceans surrounding Antarctica.

Two degrees Celsius will warm seas north of Antarctica, which will lead to stronger winds and increased snow and rain in the region.

"The westerly winds, which drive the big currents around Antarctica, will move poleward like a tightening noose," said Joellen Russell, a climate modeler at the University of Arizona who was involved in the research.

This will in turn prevent sea ice formation everywhere in the oceans off Antarctica, especially in the continent's northern latitudes, where emperor and Adélie penguin colonies are concentrated.

Ice Dwellers

Emperor penguins breed and rear their young on sea ice connected to land, called fast ice.

Adélies don't nest on sea ice but, like emperors, they forage for food among crumbling sea ice, also known as pack ice.

If sea ice disappears, the two bird species will have a harder time nesting, and could face increased competition from open-water penguin species.

In fact, some penguin species may benefit from the loss of sea ice.

For instance, ice-intolerant penguins, such as chinstraps and gentoos, are moving into the warmer Antarctic habitats once occupied by the Adélies, according to research by William Fraser of the Polar Oceans Research Group.

Since 1974, gentoos have increased in number by 7,500 percent and chinstraps by 2,700 percent, Fraser found.

Surprises in Store

Andrew Monaghan is an atmospheric scientist at the National Center for Atmospheric Research in Boulder, Colorado, who was not involved in the research.

Monaghan called the study a "very good effort" at predicting the impact of global warming in Antarctica, but he noted that many of the factors influencing climate change at Earth's poles are still not well understood.

"We don't have a good handle on climatic variability on longer time scales in Antarctica," Monaghan said.

"There could still be some surprises in store that could change the timing and magnitude of some of the warming that we'll see."

Dee Boersma, a penguin expert at the University of Washington in Seattle, has studied penguins in Argentina for 25 years with support from the National Geographic Society's Committee for Research and Exploration. (National Geographic News owns the National Geographic Society.)

"This is an excellent study, but the real problem is the increasing number of humans on the planet and their growing consumption," Boersma said.

Study co-author Ainley agreed that humans are the penguins' more immediate threat.

"The profound alteration of marine food webs by overfishing has had far, far more effects on the oceans than global climate change will have for a very long time," he said.

And global warming could make an already dire situation in Antarctica even worse, Ainley added.

"As the sea ice recedes, humans have access to fish previously protected by sea ice," he said.