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450 assessment of climate change in the southwest united statesTable 19.1 Evolution of knowledge about climate in the Southwest (Continued)2009 Southwest Assessment This Assessment Agreement Evidence Much LessLessSameMoreMuch MoreSameMoreMuch MoreEfforts are underway to identify and implement adaptationstrategies aimed at reducing these risks [to the Delta and SuisunMarsh].XXUnique tourism and recreation opportunities are likely to suffer. X XIncreasing temperatures will affect important winter activitiessuch as downhill and cross-country skiing, snowshoeing, andsnowmobiling, which require snow on the ground.Projections indicate later snow and less snow coverage in skiresort areas, particularly those at lower elevations and in thesouthern part of the region.XXXXDecreases from 40% to almost 90% are likely in end-of-seasonsnowpack under a higher emissions scenario in counties withmajor ski resorts.Earlier wet snow avalanches—more than six weeks earlier by theend of this century under a higher emissions scenario—couldforce ski areas to shut down affected runs before the seasonwould otherwise end.XXXXEcosystem degradation will affect the quality of the experiencefor hikers, bikers, birders, and others.XXWater sports that depend on the flows of rivers and sufficientwater in lakes and reservoirs are already being affected, andmuch larger changes are expected.XXAgriculture faces increasing risks from a changing climate. X XUrban areas are also sensitive to temperature-related impacts onair quality, electricity demand, and the health of their inhabitants.The magnitude of projected temperature increases for theSouthwest, particularly when combined with urban heat islandeffects for major cities such as Phoenix, Albuquerque, Las Vegas,and many California cities, represent significant stresses tohealth, electricity, and water supply in a region that alreadyexperiences very high summer temperatures.XXXX