Washington (AFP)

In the tiny part of the Antarctic continent where snow melts in the spring, mosses, lichens and grasses, flies and mites, and colonies of microorganisms have been eating, living and breeding for millions of years.

"The density is equal to, or exceeds, what is found in temperate or even tropical regions," says Peter Convey, Antarctic Terrestrial Ecologist. In places live microscopic arthropods, collembola. "There can be one million per square meter," says the scientist.

This rich biodiversity is preserved in an ancient balance by the extreme cold and isolation of Antarctica, a continent larger than Europe and the most isolated on the planet, surrounded by a powerful marine current.

But the thousands of researchers and 50,000 tourists who visit each year risk breaking this balance by bringing plants and insects with them. A grass, Poa annua, has already settled on some islands. Two flies were also imported by humans.

It may happen that species manage to fly or sail naturally from the tip of South America to a thousand kilometers, but these natural migrants do not settle. "99% of invasive species come with humans," says Peter Convey AFP, which has counted a hundred for two centuries.

The researcher argues, with a colleague of the British Antarctic Survey in a study published Wednesday in the journal Science Advances, that global warming would facilitate the implantation of invasive species, even though it would remain less marked than elsewhere on the planet, as c is the case today (the Arctic, less protected, warms up fast today).

"Climate change reduces barriers to entry, it facilitates entry and reduces problems preventing settlement," says Convey.

At the current rate of warming, the area of ​​land without permanent ice in the Antarctic Peninsula (in the west) will increase by 300% in the next century. An imported species will have much more land to colonize, he says.

With more land and more liquid water due to melting, life will explode, and probably intensify competition between species. Herbs will prevail over mosses. Local flies will compete with foreigners. The exact effect is difficult to predict.

The Antarctic Treaty (1959) enshrined the principle of protecting the Antarctic environment. While the current debate is dominated by the fear of melting ice, the authors insist that human activities in the Southern Ocean and on the continent "will, in reality, probably have a much greater impact on Antarctic ecosystems than change. climate itself.

© 2019 AFP