Columbia Plateau Ecoregion: Chapter 22 in Status and trends of land change in the Western United States--1973 to 2000

Located in eastern Washington and northern Oregon, the Columbia Plateau Ecoregion is characterized by sagebrush steppe and grasslands with extensive areas of dryland farming and irrigated agriculture. The ecoregion, which is approximately 90,059 km² (34,772 mi²), is surrounded on all sides by mountainous ecoregions: to the west, the North Cascades Ecoregion and the Eastern Cascades Slopes and Foothills Ecoregion (and to the west of it, the Cascades Ecoregion); to the south, the Blue Mountains Ecoregion; and to the east, the Northern Rockies Ecoregion (fig. 1) (Omernik, 1987; U.S. Environmental Protection Agency, 1997). The climate is Mediterranean, with cool wet winters and hot dry summers.