Combustible grass winning the west.

Combustible grass winning the West

Summer parches much of the Great Basin, a region centered in Nevada and extending out in all directions. Until about 1930, however, wildfires rarely hit the area -- largely because the native ecosystems featured such low-ignition plants as sage-brush, bunch grass, pinyon pines and junipers. Now, the rapid advance of Bromus tectorum, a weedy Eurasian grass inadvertently introduced to the United States about a century ago, is igniting concern about the future of the West's sagebrush steppe and pinyon/juniper woodlands.

Bromus, also known as cheat grass or bronco grass, dries up in the arid West around late May. From then until the November rains, it remains highly combustible. "It's like gasoline almost," says plant ecologist Dwight Billings of Duke University in Durham, N.C. Almost anything -- from lightning to the errant dropped match -- can set it off. When Bromus burns, often 30,000 acres at a time, most of its seeds survive to sow the charred expanses. Its native competitors don't recover nearly as well. Already, Bromus covers almost half the Great Basin, Billings' surveys show. And where fires have been severe, at best only 3 to 5 percent of the native plants remain.

A poor forage and shelter for the birds and animals that once called the Great Basin home, the invading Bromus is "destroying these two big biones -- the bunch grass/sagebrush ecosystem and the pinyon/juniper woodlands," Billings told SCIENCE NEWS. And the really bad news: Billings says work by a Duke colleague indicates Bromus will have an even better selective advantage under conditions expected with a greenhouse warming.