Goal for these desert troops? Bag the buffelgrass.

Volunteers take pickaxes and crowbars to the invasive weed, which is threatening the ecology of Arizona's Sonoran Desert.

from the May 31, 2007 edition

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A native of South Africa's savannahs, buffelgrass was introduced in the United States in the 1940s, after the hard lessons of the Dust Bowl. It seemed to be the answer to government officials' desperate search for a plant that would hold the soil and provide forage for cattle.

After testing and further development in Texas, its seeds were sold to area ranchers. Since then, it has marched across northern Mexico and southern Arizona and is now invading the central part of the state.

Buffelgrass thrives with very little water and germinates easily and often, producing seed heads three or four times a year, experts say. It began its wild trek through Arizona on the wind, taking root on roadsides, then spreading up surrounding hillsides. It starts in tiny low clumps and grows into larger ones that can reach three to four feet wide.

"It competes with and eventually overtakes wildflowers," says Raul Puente, curator of living collections at the Desert Botanical Garden here. "Its root system is thicker and more developed than [those of] wild plants, so it eventually chokes out all the native plants."

Perhaps more worrisome is that buffelgrass is in cahoots with wildfire. In the arid climate here, it dries and becomes very combustible, providing both fine fuel, which is a fire starter, and secondary fuel, which causes wildfires to spread.

The effect, these experts say, appears to be devastating. The magnificent saguaros, which grow nowhere else in the world, cannot survive wildfires. Neither can other cactus species such as ocotillos and barrel. Worse, buffelgrass burns hotter than garden-variety desert grasses, killing cactus seeds that are lying dormant in the soil.

Wildfires weren't unheard of here but occurred naturally only every 100 years or so. With the new tinder, they are flaring much more often. What the Sonoran Desert may ultimately have left, experts warn, are buffelgrass and other nonnative grasses.

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