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While farming and ranching are still the primary land uses in the Great Plains, urban areas provide housing and jobs for two-thirds of the region's people. The Great Plains is more rural than the rest of the US. Nearly 40% of the region's counties have populations less than 2,500 people in contrast to only 20% of rural counties in the remainder of the US. Increasing sizes and declining numbers of farms and ranches, fewer rural trade centers, and declining rural populations are recent socioeconomic trends that further contribute to the sense of remoteness of some rural counties in the Great Plains. In contrast, some Great Plains' counties with large urban centers or with scenic areas are experiencing rapid population increases and economic growth.

The US Great Plains region includes all or portions of 10 states: Montana, Wyoming, North Dakota, South Dakota, Nebraska, Colorado, Kansas, New Mexico, Oklahoma, and Texas. The location of the naturally occurring ecosystems and of agricultural lands are strongly linked to the gradients of temperature (cool in the north, warmer to the south) and precipitation (drier in the west, wetter to the east) within the Great Plains. Cool-season grasslands in the North give way to warm-season grasslands in the central and southern parts of the region, which give way to drought-adapted shrubs in the southwestern part and trees in the southeastern part.

Crop types also follow the temperature gradient, with cool-season grains such as wheat, barley, and oats dominating in the north and warm-season crops such as corn, sorghum, sugar beets, and cotton dominating in the south. The precipitation gradient influences the need for irrigation in agriculture with a higher percentage of crops grown under irrigation in the western Great Plains whereas most crops dependent on precipitation during the growing season being located in the eastern Great Plains. The extreme western Great Plains is dominated by dryland cropping and grazing because of little water available for irrigation.

The Great Plains produces much of the nation's grain, meat, and fiber. More than 70% of the Great Plains' landscape is used to produce this large proportion of the nation's food. Although agriculture dominates land use in the Great Plains, the average economic contribution is surprisingly small, only about 2% of the 1997 gross state product of the collective Great Plains states (with some higher and some lower). Over 60% of the nation's wheat and 87% of the nation's grain sorghum are produced in the Great Plains. Over 54% of the nation's barley and 36% of the nation's cotton are also produced in the region. The amazing ability of the agricultural sector to spread across climatic zones is apparent in the occurrence of both corn and wheat from North Dakota to Texas. Rearing of livestock, including both grazing and grain-fed cattle operations in the Great Plains, accounts for over 60% of the nation's total production.

Although dominated by grasslands, the Great Plains is also home to a diversity of plants and animals in shrublands, wetlands, woodlands, and forest communities. Riparian vegetation, including forests and shrublands line the banks of the region's waterways. Juniper woodlands and conifer forests are found in the South Dakota badlands and wind-deposited material forms extensive sand dune systems. For thousands of years the rich grasslands of the region have been the basis of a large grazing system supporting a diversity of large and small mammals, birds, and insects. Endemic (native) plants and animals are found throughout unique habitats in the Great Plains. The Prairie Pothole region of the northern Great Plains and the playa lakes of the central and southern Great Plains are important habitat and breeding grounds for migratory waterfowl (e.g., ducks). Fish habitats include large streams with erratically variable flow, prairie ponds, marshes and small streams, and residual pools of highly intermittent streams.

Climate determines many aspects of life on the Great Plains. Natural and human systems cope with the natural variability (day-to-day, season-to-season, year-to-year changes) in climate that characterizes the region. Great Plains' farmers and ranchers have demonstrated an uncanny ability to adapt to the range of climatic conditions and to incorporate new technologies that provide some cushion against the highly changeable weather. Periods of drought heighten the importance of water in this region.

The soil of the Great Plains, particularly the soil organic matter, is a major resource for the region. Soil organic matter can be increased by adopting new technologies (e.g., low till/no till farming practices). Increasing the organic content of the soil can improve soil health and productivity by retaining plant nutrients in the soil. Soil organic matter also increases the ability of the soil to retain water, thereby reducing flooding and erosion and lessening the need for irrigation. Increasing soil organic matter also helps to limit global warming by keeping at least some carbon dioxide (a major cause of global warming) out of the atmosphere.

The variability of weather in the Great Plains is a characterizing feature. “Normal -- years tend to be rare and extreme years are most often the common experience. Blizzards, floods, droughts, tornadoes, hail storms, thunderstorms, high winds, severe cold, and extreme heat often arrive suddenly, disrupt normal activities, and can be life-threatening.

The climate of the Great Plains is characterized by a strong north-south temperature gradient and a strong east-west precipitation gradient. Average annual temperature is less than 39˚F in the northern Great Plains but exceeds 72˚F in the Southern Great Plains. Monthly average maximum temperatures exceed 91˚F in most places on the Great Plains during at least one of the summer months. Three consecutive days of temperature over 90˚F can induce heat stress for both humans and livestock. Annual precipitation ranges from less than 7 to 8 inches on the western edge to over 43 inches on the eastern edge of the Great Plains. The spring and summer peaks in precipitation provide growing season moisture for the prairies. Growing seasons range from 110 days in the northern Great Plains to 300 days in the southern Great Plains.

Over the last 100 years the average annual temperatures in the northern and central Great Plains have risen about 2˚F, however, no warming trend has been experienced in the southern Great Plains. This warming trend in the northern Great Plains has resulted in 6 fewer days each year with temperatures less than 32˚F and in greater nighttime warming than daytime warming. Over the last 50 years, the average date of the last measurable snow (greater than 1 inch on the ground) has occurred 4 days earlier in the northern Great Plains, indicative of greater warming in the winter and spring months. Over the last 100 years, annual precipitation has decreased by 10% in some areas within the region and increased by 5 to 20% in other areas within the region. For example, Texas has seen an increase in high intensity rainfall events and has also reported significantly more area considered severely wet and significantly less area under drought conditions.

The two climate models used as the primary source of results for the National Assessment suggest a continuation of the trends seen in the Great Plains historical climate: higher temperatures, and for some areas, greater precipitation. One of the models projects higher temperatures than the other. In both models, the annual average temperature rises more than 5°F by the 2090s. Increases in temperature are greatest along the eastern edge of the Rocky Mountains. More warming is expected in the winter than in the summer. The models also suggest a greater number of heat events -- three days in a row above 90 °F. For Colorado and Oklahoma, this represents more than a doubling of the number of times such heat stress would occur. Substantial increases in the July heat index (a combination of heat and humidity), with the largest increases in the southern areas, are also projected for this region.

Annual precipitation over the Great Plains is projected to increase by at least 13% in both models by the 2090s -- but not everywhere in the region. A pattern of decreasing precipitation appears in the lee of the Rocky Mountains and is much greater in one of the models. The annual increases in precipitation are greatest in the eastern and northern parts of the Great Plains. Precipitation is likely to occur in more intense rainfall events, especially in the Southern Great Plains. Although precipitation increases are projected for parts of the Great Plains, increased evaporation from rising air temperatures is very likely to overwhelm the extra moisture from precipitation, causing soil moisture to likely decline for large parts of the region. Both climate models also suggest that, just as a normal aspect of ongoing variability, there will be years when drought conditions are likely to prevail.