Quantifying Vegetation and Habitat in the Great Basin

To estimate vegetation at risk in the Great Basin, we first quantified the total area of each landcover type present in the study area using the landcover map described in Describing Species-habitat Relationships (Comer and others 2002). The area burned in the Great Basin, especially sagebrush, increased dramatically beginning in 1994 (Connelly and others 2004). To accurately assess these landcover changes, areas in the Great Basin burned by large-scale fires since 1994 were reclassified as recently burned. We used fire data from 1994 to 2001 because the cover type map accounted for area burned prior to 1994.

The amount of habitat for each species was calculated by overlaying the landcover map—selecting only those cover types identified as habitat for the species (Describing Species-habitat Relationships )—with the species’ geographic range within the Great Basin. These habitat maps were the basis for subsequent quantification and mapping of habitats at risk for each species (Species’ Habitats at Risk (Habitat at Risk)) and for species groups (Characterizing Habitat Conditions).