Thawing icy plains a threat as rot sets in
Janet Wilson in Los Angeles
June 17, 2006
ANCIENT woolly mammoth bones and grasslands locked in a 1 million-square-kilometre stretch of Siberian permafrost are starting to thaw, with the potential to unleash billions of tonnes of carbon and accelerate global warming, Russian and American scientists have concluded.
"It's like taking food out of your freezer … leave it on your counter for a few days and it rots," said a University of Florida botany professor, Ted Schuur, describing the process in which bacteria convert decaying animal and plant matter in the soil into carbon dioxide, methane and other harmful greenhouse gases.
The study, published in yesterday's issue of the journal Science, concluded that while other global warming researchers were factoring carbon reserves in the ocean, and in current soils and vegetation on the earth into their calculations, they had overlooked vast amounts of carbon trapped in permafrost in the northern plains of Siberia and central Alaska.
If all the permafrost thawed and was released as heat-trapping carbon dioxide, it could nearly double the 730 billion tonnes of carbon now in the atmosphere, the scientists said.
What was most surprising, they said, was the size and depth of the terrain that they found could be affected, at an average of 25 metres deep and containing about 500 billion tonnes of carbon.
"It's like finding a new continent under the earth," said the lead author, Sergey Zimov. He said the vast, carbon-rich area had been buried over many millenniums by a unique layer of windborne "loess" dust that covered bones of mammoth, bison, sabre-toothed tiger and abundant grasses they fed on, then froze about 10,000 years ago into permafrost.
The research team also found that carbon stored over tens of thousands of years could bubble up from thawed soil in as little as 100 years.
Los Angeles Times |
