Ecological Setting and Status of the Great Basin

Fig. 1 - Mapped risk of displacement
by cheatgrass

The Great Basin ecoregion spans more than 29 million ha from the eastern Sierra Nevada Mountains in California to central Utah east of the Great Salt Lake (Figure 1, Figure 2). Federal lands dominate (80 percent) the landscape; thus, the role of Federal agencies is paramount in conservation planning and management in this area. Although classified as arid, with mean annual precipitation of 216 mm, precipitation is highly variable and falls primarily during winter and spring. Climate change has been pronounced during the past 150 years, with warmer temperatures and increased carbon dioxide levels (Tausch and Nowak 2000, West 1999). Riparian systems of the Great Basin are particularly sensitive to effects of climate change (Chambers and Miller 2004).

Fig. 2 - Great Basin Ecoregion

Fig. 3 - Sagebrush ecosystem in the U.S.

The Great Basin supports one of the largest extant concentrations of sagebrush in North America at more than 8 million ha (29 percent of the landcover in the ecoregion). Indeed, among ecoregions of the sagebrush biome, the Great Basin ranks second in total extent of sagebrush, exceeded only by the Columbia Plateau (Wisdom and others 2005a) (Figure 3). Although sagebrush loss in the ecoregion has occurred from a variety of causes, wildland fires have been especially devastating. More than 500,000 ha of sagebrush (6.4 percent of the sagebrush in the ecoregion) burned between 1994 and 2001 (Wisdom and others 2005a). Closely tied to losses from wildfire is the spread of cheatgrass (Bromus tectorum), introduced to the United States in the 1800s and now a pervasive problem throughout much of the arid West (Billings 1994, Booth and others 2003, Peterson 2006). Cheatgrass is estimated to currently occupy more than 2 million ha (7 percent) of the Great Basin (Bradley and Mustard 2006).

Beyond its reputation as a stronghold for sagebrush, the Great Basin is recognized as an area of rich biodiversity, with its extremes of topography and climate contributing to a diverse assemblage of endemic plants and animals (Nachlinger and others 2001, Ricketts and others 1999). Among terrestrial ecoregions of North America, the Great Basin Shrub Steppe was among the most diverse in both number and endemism of vascular plants (Ricketts and others 1999).