Early explorers wrote about the vast sea of sagebrush that stretched in front of them. Today, the consequences of land-use practices, invasion by exotic plants, and altered disturbance regimes have touched virtually all of these seemingly endless expanses. Increasing human populations in the western United States, the infrastructure necessary to support these populations, and a growing demand for natural resources exert a large influence. Changes within the biome have resulted in its designation as one of the most endangered ecosystems in North America.