Deserts

DESERTS

DESERTS. Definition has been the central problem in the history of the deserts of the United States. The need to ascertain the limits of arability and the difficulty of establishing such boundaries where precipitation fluctuates unpredictably constitute a basic developmental theme for more than half the nation. Archaeological evidences of prehistoric Native American communities indicate that droughts occasioned recurrent disaster to agricultural

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societies long ago, as now, in border areas. In 1803 President Thomas Jefferson, seeking congressional support for exploration of the upper Missouri River, summarized existing knowledge of newly purchased Louisiana in describing it as a region of "immense and trackless deserts" but also, at its eastern perimeter, as "one immense prairie "—a land "too rich for the growth of forest trees." The subsequent expedition of Meriwether Lewis and William Clark (1804–1806) marked the official beginning of American efforts to elaborate the description.

Until the 1860s a conception prevailed that the vast province west from the meridian of Council Bluffs, on the Missouri River, to the Rocky Mountains, between thirty-five and forty-nine degrees north latitude, was a "Great American Desert." The explorations of Lewis and Clark, Zebulon Pike, and Stephen Harriman Long, followed by the experiences of traders to Santa Fe, Rocky Mountain fur trappers, immigrants to Oregon and California, soldiers along the Gila Trail, surveyors for transcontinental railroads, and prospectors throughout the West confirmed the appellation.

While commentators agreed that agriculture could have no significant role in the region, they did occasionally recognize that the Great Plains, the mountain parks, and the interior valleys of California and the Northwest afforded excellent pasturage. As livestock industry developed in these areas during the period from 1866 to 1886, redefinition of the limits of aridity evolved. Maj. John Wesley Powell's surveys and, notably, his Report on the Lands of the Arid Region (1878) expressed the new point of view; agriculture, Powell asserted, could be profitably conducted in many parts of the West, but only as an irrigated enterprise and generally as a supplement to stock growing. The collapse of open-range ranching in the mid-1880s emphasized the need for expanded hay and forage production and gave impetus to development of irrigation programs. But Powell's efforts to classify the public lands and the passage of the Carey Desert Land Grant Act of 1894 raised controversy. States east of the 104th meridian were excluded, at the request of their representatives, from the application of the Carey legislation. Farmers during the 1880s had expanded cultivation without irrigation nearly to that meridian in the Dakotas and even beyond it in the central plains. Many were convinced that "rainfall follows the plow." They saw no need to assume the costs and the managerial innovations of supple-mental watering. A new conception of the boundaries of aridity was emerging.

Drought in the mid-1870s had driven a vanguard of settlers eastward from the James River Valley, a prairie zone normally receiving more than twenty inches of annual rainfall. Drought in the period 1889–1894 forced thousands back from the plains farther west, where average precipitation ranges between fifteen and twenty inches annually. As normal conditions returned, however, farmers in the first two decades of the twentieth century expanded cultivation across the plains to the foothills of the Rockies—in Montana, Colorado, and New Mexico—and in many areas beyond—Utah, Idaho, the interior valleys of California, and eastern Oregon and Washington. Irrigation supplied water to only a small portion of these lands. Dry farming—a specialized program that, ideally, combines use of crop varieties adapted to drought resistance, cultivation techniques designed to conserve moisture, and management systems that emphasize large-scale operations—provided a new approach to the problem of aridity. The deserts, promoters claimed, could be made to "blossom like the rose."

When severe droughts again returned from 1919 to 1922, and from 1929 to 1936, assessment of the effectiveness of dry farming raised new concern for defining the limits of aridity—an outlook most strongly expressed in the reports of the National Resources Board of the mid-1930s but one that still permeates the writings of agricultural scientists. Long-term precipitation records, with adjustment for seasonality and rate of variability in rainfall, humidity, temperature, and soil conditions, now afford some guidance to the mapping of cultivable areas.

By established criteria a zone of outright desert (less than five inches average annual precipitation) ranges from southeastern California, northward through the western half of Nevada, nearly to the Oregon border. Because cropping without irrigation is impracticable when rainfall averages less than ten inches annually, climatic pockets found in all states west of the 104th meridian—most prevalently in Arizona, central New Mexico, eastern Nevada, Utah, and the lee side of the Cascades in Oregon and Washington—may also be defined as arid. Semiaridity—an average precipitation of from ten to fifteen inches annually—characterizes the western Dakotas, much of Montana, and large sections of eastern New Mexico, Colorado, Wyoming, Idaho, Oregon, and Washington. There dry farming may be successful but only when management programs include allowances for recurrent drought. Throughout much of the semiarid region livestock production predominates, with cropping to afford feed and forage supplementary to native short-grass pasturage. In many areas, however, the possibility of raising wheat of superior milling quality, which commands premium prices, encourages alternative land utilization. The costs of marginal productivity must be carefully weighed.

Eastward, roughly from the Missouri River to the ninety-eighth meridian and curving to the west through the central and southern plains, is a subhumid zone, in which rainfall averages from fifteen to twenty inches annually, an amount sufficient, if well distributed, to permit cultivation without recourse to specialized programs but so closely correlated to the margin of general farming requirements that a deficiency occasions failure. Almost every spring, alarms are raised that some areas of the vast wheat fields extending from the central Dakotas, through western Kansas and Nebraska and eastern Colorado and New Mexico, into the panhandles of Oklahoma and Texas have suffered serious losses. There the problem of defining limits of arability is yet unresolved; the boundaries of America's deserts and arid regions remain uncertain.

BIBLIOGRAPHY

Fite, Gilbert C. The Farmers' Frontier, 1865–1900. New York: Holt, Rinehart and Winston, 1966.

Goetzmann, William H. Exploration and Empire: The Explorer and the Scientist in the Winning of the American West. New York: Knopf, 1966.

Hargreaves, Mary W. M. Dry Farming in the Northern Great Plains, 1900–1925. Lawrence: University Press of Kansas, 1993.

Limerick, Patricia Nelson. Desert Passages: Encounters with the American Deserts. Albuquerque: University of New Mexico, 1985.

Teague, David W. The Southwest in American Literature and Art: The Rise of a Desert Aesthetic. Tucson: University of Arizona Press, 1997.

Mary W. M. Hargreaves / a. r.

See also Agriculture ; Death Valley ; Great Plains .