Deserts can fight global warming

Tuesday, Jan. 25, 2005 | 8:32 a.m.

Nevada scientists studying the desert and its ability to absorb gases that contribute to global warming were startled to discover that an arid patch in Southern Nevada may reduce its uptake of carbon dioxide in the future.

Since 35 percent of the Earth's surface is arid or semi-arid, what happens to increasing levels of carbon dioxide, a gas that contributes to global warming, is important to the rest of the planet because deserts are expanding.

The research project has drawn experts on desert environment from UNLV, the Desert Research Institute and UNR, with results that are gaining national attention.

The Desert Research Institute, a nonprofit research division of the University and Community College System of Nevada, added a new dome tent to gather more specific data about the plants under study, said Jay Arnone, an associate research professor at the DRI's Division of Earth and Ecosystem Sciences.

Scientists from the Desert Research Institute and UNLV carved nine circles into 200 acres of otherwise undisturbed desert on the Nevada Test Site eight years ago.

The surprising scientific results from the study suggest that deserts may take up less carbon dioxide as Earth continues to heat up.

"The Mojave Desert ecosystems we're studying are currently net 'sinks' for carbon dioxide," Arnone, the lead scientist on the project, said, meaning that deserts could soak up as much of the gas as some forests or grasslands.

However, as people continue to increase their use of oil and gas for transportation, industry and heating, the absorption could slow, Arnone said.

"So the good news is that desert ecosystems like the Mojave will likely continue to absorb carbon dioxide into the future, but the bad news is that these ecosystems that cover more than 35 percent of the Earth's land surface, will probably absorb significantly less in the future than they do now," Arnone said.

The outdoor laboratory at the Test Site is called FACE, short for Free Air CO2 Enrichment, and it has been open to the air for eight years.

The nine large circles of suspended PVC pipe that look as if they are part of an alien spacecraft landing zone deliver carbon dioxide at the surface for natural Southwestern plants encircled by the pipe.

The nine rings are separated into three distinct study units. Three experimental plots are exposed to current carbon dioxide levels, another three plots are not being exposed to any gas and the last three receive carbon dioxide levels expected in the year 2050.

It is the only arid-ecosystem research plot designed to permit a controlled release of elevated carbon dioxide levels into the air around the vegetation without disturbing natural conditions such as rain or snowfall or a desert tortoise passing through the parcels.

Stan Smith, biology professor at UNLV who has been part of the project since it began, said that the carbon dioxide study's results are preliminary.

"It will be interesting to see if we get this 30 percent reduction (of carbon dioxide absorbed) this year, which is a wet year with high plant production," Smith said. "I suspect we may not."

Scientists need to measure how much carbon dioxide is reduced through several wet and dry cycles, Smith said. The experiment should also be conducted in other deserts.

If carbon dioxide is not absorbed, "that would send more greenhouse gases into the atmosphere and therefore contribute to global warming," Smith said.

The 14-foot-wide dome tent Arnone uses has 48 individual tent tubes that allow scientists to dismantle the dome like a camping tent and store it in two duffel bags.

When scientists go to the desert to collect samples, the dome tent is sealed to the desert floor using a foam rubber gasket.

Inside, a fan circulates the air while an infrared gas analyzer mounted inside the dome takes readings of carbon dioxide and water vapor.

A communication cable transmits the readings from the analyzer to a laptop computer outside the dome.

As part of the project, the scientists are asking questions such as what happens to desert watersheds if carbon dioxide levels rise, what the gas does in the soils and whether nitrogen will drop in the atmosphere and disrupt plant growth as well.

Earlier results from the study revealed that grasses thrived, edging out bigger and more stable plants, posing the potential for more and bigger brush fires in the Mojave Desert as the climate warms and carbon dioxide increases in the overall atmosphere.