Large areas of Earth drying up: study

09:30, October 13, 2010      
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Mainly due to climate change, large swaths of Earth have been drying up, posing a threat to the ecosystem, a new study available here on Tuesday finds.
The drying areas are mainly in the Southern Hemisphere, including large parts of Australia, Africa and South America, according to the study conducted by researchers at Oregon State University.
In large portions of the world, soils are now becoming drier than they used to be, releasing less water and offsetting some moisture increases elsewhere, said the study published in the Oct. issue of the journal Nature.
The study is the first major one of its kind to look at the movement of water from the land to the atmosphere, called " evapotranspiration," on a global scale.
Most climate models have suggested that evapotranspiration would increase with global warming, because of increased evaporation of water from the ocean and more precipitation overall (water that can evaporate).
Because the data only goes back for a few decades, the researchers say they can't be certain whether the change is part of the natural variability of climate or part of a longer-lasting global change.
One possibility, though, is that on a global level, a limit to the acceleration of the hydrological cycle (the transfer of water between land, air and sea) on land has already been reached.
If that's the case, the consequences could be serious. They could include reduced terrestrial vegetation growth, less carbon absorption, a loss of the natural cooling mechanism provided by evapotranspiration, more heating of the land surface, more intense heat waves and a "feedback loop" that could intensify global warming, the study said.
"We didn't expect to see this shift in evapotranspiration over such a large area of the Southern Hemisphere," said study co- author Beverly Law, a professor of global change forest science.
"It is critical to continue such long-term observations, because until we monitor this for a longer period of time, we can' t be sure why this is occurring."
Source: Xinhua
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