June 23, 2008

Southern California pollution sinking into desert

Orange County Register

Eastbound Interstate 40 in the East Mojave Desert.

Deserts suck.

Suck carbon dioxide, that is. The Mojave Desert is absorbing more of the airborne pollutant than previously thought, says Lynne Fenstermaker, a scientist at the Desert Research Institute in Nevada. And it may be that this nearby desert is doing more than absorbing car exhaust from our freeways. The study by Fenstermaker and colleague Jay Arnone has found that the Mojave can absorb as much carbon dioxide as a temperate forest.

“Without deserts, the annual rate of [man-made] carbon dioxide rise might be twice as rapid as it is presently and might therefore promote more rapid global warming,” Arnone said in a recent news release.

And since deserts make up more than 30 percent of Earth’s land surface, if all deserts were absorbing as much as the Mojave, “then the amount of carbon dioxide taken up each year would match the amount emitted to the atmosphere globally through burning of fossil fuels,” Arnone says.

Carbon dioxide in the Mojave Desert is absorbed both by plants and by micro-organisms in the top layer of the soil. This “microbiotic crust” contains lichens, mosses and blue-green algae. All of these do some type of photosynthesis, which turns carbon dioxide into sugar, which they then use for food.

You wouldn’t think that the sparse vegetation on a desert would be able to take up so much carbon dioxide, but in an El NiƱo year, where the deserts get a large amount of rainfall, the population of annuals can be quite high, Fenstermaker says. And the more plants there are, the more carbon dioxide they inhale.

At this point, they’re not sure exactly where the carbon dioxide is going. That is, if the vegetation or the soil layer is doing more of the work. But more studies are planned. They also want to take measurements in deserts worldwide, to see if other deserts suck up as much carbon dioxide as the Mojave.

The Mojave study is funded by the Department of Energy, Terrestrial Carbon Processes project.