It's well known that trees "breathe" in carbon dioxide and "exhale" oxygen. The giants of the plant kingdom keep temperatures down and filter the air, leading conservationists to hail trees as one of mankind's best weapons against global warming.

But researchers at Washington State University say deserts and other arid ecosystems are also adept at soaking up excess CO2.

In a recent study, published this week in the journal Nature Climate Change, researchers found that the sands and small plants of dry climes can do a surprisingly good job of absorbing carbon dioxide. Unlike trees, which store CO2 in their plant matter, the brush of arid ecosystems mostly stores excess carbon dioxide in the microorganism-rich soil around its roots.

"It has pointed out the importance of these arid ecosystems," said R. Dave Evans, speaking on the significance of the study.

Evans, a professor of biological sciences at WSU, teamed up with several other ecologists and climatologists to study how the Mojave Desert would react to increased levels of carbon dioxide. Over a period of ten years, Evans and his colleagues exposed small patches of the desert to increased levels of CO2 -- amounts they say are equivalent to the projected atmospheric makeup in 2050.

After a decade of exposure, the scientists excised large chunks of the desert and measured carbon dioxide levels. "We just dug up the whole site and measured everything," said Evans. What he and his fellow researchers found was that the arid grounds of the desert were surprisingly good at soaking up the climate-warming gas.

"They are a major sink for atmospheric carbon dioxide," explained Evans, referring to arid ecosystems. "So as CO2 levels go up, they'll increase their uptake of CO2 from the atmosphere. They'll help take up some of that excess CO2 going into the atmosphere. They can't take it all up, but they'll help."

Although trees and forests are much more efficient at storing CO2, this latest study suggests deserts could play an increasingly important role in mitigating climate change due to their large geographic presence.

The study's authors say as CO2 levels continue to rise, deserts will likely soak up a larger share, by 2050 arid ecosystems could draw in 15 to 28 percent of all CO2 absorbed by land surfaces.

[Washington State University]