"That's also an issue," de Poorter said.
John Priscu is an environmental scientist at Montana State University in Bozeman who has spent 22 years studying microscopic organisms in the McMurdo Dry Valleys of Antarctica.
(See an interactive map and wallpaper photos of Antarctica.)
He says the climate there is actually cooling, but the contamination of the environment with human bacteria and bacteria from other regions of Antarctica is a real concern.
For example, he says, researchers have found seals and penguins infected with bacteria from the sewage at the McMurdo Station research base.
At the nearby Scott Base, seals are infected with canine distemper, a virus passed to them by researchers' dogs.
Priscu and his colleagues wear special suits whenever working in ice-covered lakes to prevent contamination. Researchers also follow strict protocols to make sure equipment used to explore one region does not transfer bacteria to another.
Priscu is also embroiled in a debate over whether humans should be allowed to drill for research purposes into the pristine waters of Lake Vostok, the largest ice-covered lake in Antarctica, and risk contamination with human-borne bacteria.
(Read "Under-Ice Lakes in Antarctica Linked by Buried Channels" [April 2006].)
"One group of people argues that it doesn't matter. What can live there?" he said.
Human bacteria thrive in an environment that is 98.6 degrees Fahrenheit (37 degrees Celsius). The lake is just above freezing, shielded from light, and poor in nutrients, the argument goes.
"The thing is, we're finding more and more extremophiles out there," Priscu said, referring to organisms that can survive in extreme environments such as Lake Vostok.
And in places like the Antarctic Peninsula, where newly exposed soils are hosting new exotic species such as turf grass, bacteria that used to have no means to survive might now thrive.
"Antarctica has a relatively nondiverse ecosystem compared to temperate ecosystems, but as it warms up the environment will start playing host to a broader range of organisms," Priscu said.
According to de Poorter, the alien invasion of Antarcticaat least on landis not of "plague proportions" yet but is a sign of things to come.
"It's more a question of becoming very much aware of it and working on the prevention angle," she said.
In the water, the situation could be worse: Nobody has a good grasp on what organisms are therenative or invasive, she adds.
"I think awareness is growing," she said. "Part of that is awareness of very bad impacts elsewhere is starting to grow as well. It goes hand in hand."
The growing awareness of invasive species led to the adoption of new measures to reduce the risk from nonnative species at last month's Antarctic Treaty Consultative Meeting in Edinburgh, Scotland.
As a first step, visiting ships are being asked to dump their ballast water before arriving at the ocean that surrounds Antarctica.
Ultimately de Poorter hopes Antarctica will remain pristine, in part for philosophical reasons.
"It still sparks the imagination as the last place on Earth which is sort of like a symbol of how people and the environment can get along," she said.
"So I think it's good we have this chance to be very proactive and protect it better than we've managed to do with the rest of the world."
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