A Greenhouse in the Desert 

How will global warming affect the world's deserts? Scientists in Nevada predict potentially heartbreaking outcomes.

Imagine a future in which hundreds of thousands of people in the more arid parts of the country flee wildfires. Imagine a future in which many of those people never return home because the blazes have left their property smoldering husks. Imagine it happening with ever-more-increasing frequency until it's hard to tell where one fire season ends and the next begins.

Hard to imagine a future like that? Then maybe it's easier to remember this summer's fire season, in which fires in the American West and Southwest forced the evacuation of more than a half-million people and burned thousands of homes. It's particularly frightening when you consider that much of the land in California and the Southwest is arid or semiarid.

Scientists generally don't describe ecological changes in such apocalyptic terms. But it's hard not to when faced with the early results of major experiments being conducted at the Nevada Desert Research Center. These experiments are designed to show the impacts of soaring levels of atmospheric carbon dioxide on desert environments.

"We need to see how natural ecosystems are responding to changes in the global climate," Desert Research Institute scientist and project director Lynn Fenstermaker said. "In particular, we are interested in how well certain ecosystems are going to be able to sequester the additional carbon that's being produced by fossil-fuel burning."

Rising carbon dioxide levels in the atmosphere are one of the main causes of global warming and could cause all kinds of environmental mischief, particularly in sensitive desert ecosystems. These changes could have devastating consequences, with effects including increased growth rates for plants, increased rain, and shifting varieties of plants and animals. Scientists warn that these transformations may allow invasive, nonnative species to gain footholds. And with the added fuel on the ground will come bigger and more destructive fires.

One project to study these effects is at the Nevada Desert FACE Facility. FACE is an acronym for Free-Air carbon dioxide Enrichment. It's a ten-year collaboration between Nevada's universities, the Desert Research Institute, the National Science Foundation, Brookhaven National Laboratory, and the Department of Energy.

The FACE facility is allowing scientists to raise the carbon dioxide level in large plots of land. For this project, the concentration of carbon dioxide is raised by 50 percent above the present atmospheric levels in three plots in the Mojave Desert — North America's driest ecosystem. It's essentially done by fumigating the area with the greenhouse gas.

"Early results have shown that when we have a wet winter, an El Niño winter, we have invasive grass species producing a lot more and a lot bigger plants [including red brome, a relative of cheat grass]. This particular species leaves a lot of dead biomass on the surface, and then you get lightning strikes and then these nice rangeland fires. ... So if we see an increase in the El Niño cycle, we may see an increase in the frequency of the fire cycle."

The irony is that the wildfires also contribute to the carbon load in the atmosphere. In fact, large fire seasons can release more carbon into the air than all the vehicles in the state in a year.

Experiments like those at the Nevada Desert Research Center are necessary because some 40 percent of the earth's land surface is arid or semiarid, with more land becoming desert each year. This process — the degradation of formerly productive land, often caused by humans — is called desertification. It's already responsible for an unknown number of deaths. For example, according to US Geological Survey documents, between 1968 and 1973 the desertification-related Sahel drought in Africa led to the deaths of up to a quarter-million people and the collapse of the agricultural bases of five countries.

Can increasing carbon dioxide levels in the atmosphere cause devastating fires, more powerful hurricanes, decreased land productivity, and inconceivable starvation? It's hard to imagine that sort of future — maybe it's easier just to remember it's already happened.

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