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222 assessment of climate change in the southwest united statesFigure 11.3 Depth towater of irrigationwells. Source: USDA(2010).The livestock sector, especially cattle ranching and dairies, is also economically importantin the region. Cattle account for most of the agricultural sales in many New Mexicoand Colorado counties (Figure 11.1). Cattle ranches rely on rain-fed forage on grazinglands, making these enterprises sensitive to changes in climate. Much acreage and irrigationwater is devoted to alfalfa and other hay, which provide important forage for theregion’s dairies as well as supplemental cattle feed.Other major field crops include cotton in California, Arizona, and New Mexico; durumwheat in Southern California and Arizona; winter wheat in Colorado and California;and corn in eastern Colorado. An emerging challenge to crop production is the rise ofglyphosate-resistant (i.e., herbicide-resistant) weeds (Price et al. 2011; CAST 2012; Norsworthyet al. 2012).11.2 Implications for Specialty CropsThe future presents special challenges and opportunities for producers of high-valuecrops such as fruits, vegetables, and nuts. Demand for these crops is projected to increaseover the next forty years, correlated with expected population and income growth in theUnited States and throughout the Pacific Rim (Howitt, Medellín-Azuara, and MacEwan2009, 2010). Compared to field crops, demand for these high-value crops is price inelastic,meaning that demand falls little with price increases. This also means that smallreductions in output lead to relatively large increases in price. Thus, price increasesthat accompany climate-induced losses in output can partially offset the reduced volumesold and thereby buffer producers of these crops from the effects of climate change(though there are obvious increased costs for consumers).Climate change implies that locations best suited for production of high-value cropswill change over time. Fewer frosts may make production of certain vegetables andtree crops more viable in some regions. Yet, for some stone fruits and nuts that requirea minimum amount of chill time, i reductions in chill hours from a warming climatemay reduce the profitability of production in areas where they are currently grown. In