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Grasslands compose a large portion of the United States west of the 100th meridian. Although these areas receive too little rainfall to sustain a forest, the pioneers that settled the western frontier of the United States found dense foliage for grazing sheep and cattle. Today, a large portion of these "rangelands" is administered by the federal Bureau of Land Management, which leases grazing rights to private ranchers. Much of the private land is irrigated for agriculture.
 The impacts of climate change on grasslands has not been studied in the same detail as the implication for forests. Nevertheless, the existing research suggests a number of likely outcomes. Perhaps most importantly, climate change could harm grazing activities on both federal and private lands. Availability of water in these areas is often the single most important factor determining the value of land for grazing. The decline in western water availability suggested by several studies would seriously decrease the economic viability of grazing on these lands. Because grazing on the open range accounts for a small and declining fraction of U.S. cattle, national beef production would not be seriously impaired.
Changing climate is also likely to alter both the geographical extent and the plant composition of rangelands. If a drier climate causes some areas of the Southeast or Midwest to lose their ability to sustain a forest, the terrain in those areas may come to resemble the landscape of the open range. A wetter climate, by contrast, might enable forests to grow in areas that are now grasslands, while also enabling range grasses to grow in areas that are deserts today. Within existing rangelands, elevated levels of carbon dioxide may induce a shift from grasses toward shrubs and other woody plants.
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