Shifting ice a problem for Antarctica penguins

Friday, March 12, 2010

British Antarctic Survey / AP

Emperor penguins and chicks in Antarctica are the most severely threatened by impending climate changes, the report says. The birds need solid sea ice to lay eggs and raise chicks on.

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Shifting sea ice around Antarctica is already disrupting penguin colonies as the world's climate warms, according to a new report by a team of polar scientists.
The researchers looked at the complex relationship between emperor and Adelie penguins and their changing habitats and studied how a projected temperature increase in coming decades of 2 degrees Celsius, or 3.6 Fahrenheit, might affect the way the animals build nests, find food and raise their young.
Emperor penguins - the largest of all the awkward birds that thrive only in cold climates - are the most severely threatened by oncoming changes, the report says. The birds live, lay eggs and raise chicks on solid sea ice, but when that "fast ice" thins and breaks up as temperatures rise, their habitat shrinks, the report notes.
But the slightly smaller and more agile Adelie penguins are also being forced to shift their nesting grounds when increased snowfalls cover the rocky terrain where they build their nests and have raised their young for millennia, the researchers say.
At the very least, the report states, the penguins' range stands to be compacted, "increasing susceptibility to the effects of warming."
The study was led by David Ainley, a penguin specialist with a Los Gatos ecological consulting firm who spent 10 months on the snowbound continent. The research was supported primarily by the National Science Foundation and published by the Ecological Society of America.

Faster warming expected

The Intergovernmental Panel in Climate Change has forecast that, by the end of this century, the world's climate will have warmed by 2 degrees Celsius. But Ainley and his colleagues calculate that the 2-degree "benchmark" will be reached between 15 and 42 years from now.
The winds of the "polar jet stream" that sweep around the continent, Ainley said in an interview, have become stronger and are causing greater upwelling of ocean currents in many areas along the coast. That means large areas of thick ice are becoming thinner, while areas of open water - known as "polynyas" - are growing larger.
Those polynyas are critical to the lives of the penguins because, the report says, "they reduce the commuting time and energy expenditure between colony and food supply" - namely, fish. But the report adds, "the factors that bring increased polynyas also bring decreased sea ice thickness, a direct problem for emperor penguins."
The most deadly effect of the changes was already visible 30 years ago among emperor penguins on Adelie Land, along Antarctica's east coast, where the 2005 Academy Award-winning documentary "The March of the Penguins" was filmed, Ainley said.
Winds there, at Pointe Géologie, swept the solid ice where female penguins laid their eggs and the male emperors kept the eggs warm and reared the chicks. Under those fierce winds, the thinned and unstable ice broke off. Though the males could swim, the chicks drowned. Within a decade, the emperor colony's population dropped from 6,000 pairs to 3,000, Ainley said.

Another decline forecast

In his group's report, the scientists foresee another significant population decline among emperor Penguins at Pointe Géologie in the next few decades.
"There's been a transformation in the last couple of decades, particularly on the other side of the continent along the Antarctic peninsula where the disappearance of sea ice has been dramatic," Ainley said.
The report warns that increased snowfall caused by warming temperatures "causes problems, as Adelie penguins cannot find nesting stones or snow-free nesting habitat."
In addition, because Adelie penguins must dive for their fish beneath pack ice, the birds must swim farther from land for their food as those broad floes melt - another threat to the survival of their colonies, Ainley said.

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