Wildlife risk as Antarctic cools

Antarctic temperatures are baffling scientists

By the BBC's Helen Sewell

The number of animals living in the largest ice-free area in Antarctica is dropping rapidly as the continent cools, according to ecologists from the United States.

Generally climate prediction models suggest that the Antarctic should be heating up as a result of global warming, but it is mysteriously getting colder.

As it cools scientists say that animals are disappearing at a rate of 10% each year.

Ecologists from the United States have been studying life in the McMurdo Dry Valleys region of Antarctica - a desert-like, mountainous area of bare soil and permanently frozen lakes.

Monitoring

The area is so inhospitable that the only animals to survive there are microscopic. They rely on the water formed when small amounts of ice thaw each summer, but their numbers are dwindling.

In a paper in the journal Nature, scientists explain how they monitored the ecosystem for 14 years.

Between 1986 and 2000 they saw animal numbers fall by 10% each year. This coincides with an annual drop in summer temperatures and a consequent reduction in the amount of melt water available.

Meanwhile plants and microbes which once flourished in the freezing lakes are also disappearing.

Reduced photosynthesis

The ecologists say the drop in temperatures means the surface ice no longer gets thin enough in summertime for the sun's rays to penetrate and for the plants to photosynthesise efficiently.

Antarctic winds which generally heat the region have also dropped over the past 14 years.

Only one relatively small part of the continent is warming up - the Antarctic Peninsula, the region nearest to South America.

But the ecologists say the rest of the Antarctic is getting colder, as global warming heats the rest of the planet, and they have no idea why.

They say they will continue to monitor the Antarctic ecosystem while climate experts puzzle over the mystery.