Ecosystem Services and Western U .S . Rangelands

Rangelands are expansive, unimproved lands located in arid or semi–arid regions, spanning a variety of landscapes including savannahs, high and low altitude deserts, mountain meadows, and tundra. Rangelands are generally unsuitable for crop production due to aridity, topography, and extreme temperatures. Rangelands support varying mixtures of native and nonnative grasses, grass–like plants, forbs, or shrubs which provide forage for free–ranging native and domestic animals (Stoddart, Smith and Box, 1975). There are more than 760 million acres of rangelands in the United States, including Alaska, comprising 33% of the nation’s total land base (USDA–USFS, 1989a). While exact determinations are unavailable, it is estimated that more than 50% of U.S. rangelands are privately owned, 43% are owned by the federal government, with the remainder owned by state and local governments (National Research Council, 1994). Approximately 262 million acres of U.S. rangelands are controlled by the U.S. Forest Service (USFS) and the U.S. Bureau of Land Management (BLM) and leased to private individuals for the purpose of land– extensive livestock grazing (CAST, 1996). Many more acres of rangelands in the 11 western states1 are controlled by state or local government agencies and leased for livestock grazing, with all these states having a high degree of intermingled public and private ownership of rangelands. Arid and semi–arid rangelands in the western United States are characterized by low and variable precipitation, high evaporative demand, nutrient poor soils, high spatial and temporal variability in plant production, and low net primary production (Havstad et al., 2007). These rangelands are often subject to desertification or invasion by shrubs and other woody plants as a result of drought, low resilience, and past management practices. Increased woody