Much of the landscape of the intermountain American West has been transformed, not only by the plow and real estate developer, but by a remarkably adaptive plant. Since its introduction, probably with seed wheat in the 19th century, Bromus tectorum, known variously as downy brome or cheatgrass, has completely replaced native vegetation over large areas of the intermountain West, leaving landscapes entirely different from what they looked like 100 years ago. "We have the dubious distinction," says botanist Richard Mack, "of living in an area that provides one of the world's best examples of the transformation of vegetation through an alien species."