At least 46 exotic weeds occur in the Sagebrush Sea. [1] Livestock grazing, fire, agriculture, off-road vehicle use, oil and gas drilling and development contribute significantly to the introduction and spread of invasive species. Estimates of the rapid spread of weeds in the West include 2,300 acres per day on BLM lands and 4,600 acres per day on all western public lands. [2] Invasive species, including weeds and other organisms, are the second leading cause of species endangerment in the United States. [3]

Cheatgrass invasion on riverbank in eastern Oregon (photograph taken from river). - Mark Salvo

Pale tan cheatgrass dominating sagebrush and crested wheatgrass seedings on Bureau of Land Management lands. In the 1960s and 1970s, BLM burned, sprayed and plowed sagebrush to plant crested wheatgrass (a soil-depleting Asian species) for livestock forage. Large fires swept the increasingly weedy and heavily stocked lands of in recent decades, prompting BLM to plant even more Asian grasses in the name of fire restoration, which led to even more livestock grazing. The high cattle numbers have caused cheatgrass and now noxious weeds to expand and choke out understories in native plant communities and wheatgrass seedings. - Western Watersheds Project

The worst invader of the Sagebrsuh Sea is cheatgrass, a flammable, but fire-loving non-native grass that is now the dominant species on 100 million acres - 158,000 square miles - of the Intermountain West. [4]

"Cheatgrass is a species that thrives in disturbed, and especially burned, areas. It can even increase fire frequency, favoring itself and potentially inhibiting perennial seedling establishment. A cheatgrass invasion into sagebrush habitat can lead to an eventual conversion of sagebrush/grass (perennial) community to sagebrush/grass (annual) or annual grass rangeland. . . . In some cases, cheatgrass invasion encourages other exotic species such as knapweed and thistle." [5]

Cheatgrass monoculture. - Mark Salvo