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In many regions, over 75% of the usable topsoil was blown away in the course of the storms from 1930 to 1940, but there was a high degree of variation in the degree to which the land was degraded. Aside from the short-term economic consequences caused by the mass migration of 2.5 million people out of the plains states, there were severe long-term economic consequences of the Dust Bowl.
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Dust Bowl conditions fomented an exodus of the displaced from Texas, Oklahoma, and the surrounding Great Plains to adjacent regions. More than 500,000 Americans were left homeless. 356 houses had to be torn down after one storm alone. Many Americans migrated west looking for work. Some residents of the Plains, especially in Kansas and Oklahoma fell ill and died of dust pneumonia or malnutrition.
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Causes
During early European and American exploration of the Great Plains, the region in which the Dust Bowl occurred was thought unsuitable for European-style agriculture; the region was known as the Great American Desert. The lack of surface water and timber made the region less attractive than other areas for pioneer settlement and agriculture. Following the Civil War, settlement was encouraged by the Homestead Act, the transcontinental railroad, and waves of new immigrants, and cultivation increased. An unusually wet period in the Great Plains mistakenly led settlers and the federal government to believe that "rain follows the plow" (a popular phrase among real estate promoters) and that the climate of the region had changed permanently. The initial agricultural endeavors were primarily cattle ranching with some cultivation; however, a series of harsh winters beginning in 1886, coupled with overgrazing followed by a short drought in 1890, led to an expansion of land under cultivation.
Continued waves of immigration from Europe brought settlers to the plains at the beginning of the 20th century. A return of unusually wet weather confirmed a previously held opinion that the "formerly" semi-arid area could support large-scale agriculture. Technological improvements led to increase of mechanized plowing, which allowed for cultivation on a greater scale. World War I increased agricultural prices, which also encouraged farmers to dramatically increase cultivation. In the Llano Estacado, the area of farmland doubled between 1900 and 1920, and land under cultivation more than tripled between 1925 and 1930. Finally, farmers did not use appropriate practices for the environment, but agricultural methods that allowed erosion. For example, cotton farmers left fields bare over winter months, when winds in the High Plains are highest, and burned the stubble (as a form of weeding prior to planting), both depriving the soil of organic nutrients and increasing exposure to erosion.
The increased exposure to erosion was revealed when a severe drought struck the Great Plains in 1934. The native grasses that once covered the prairie lands for centuries, holding the soil in place and maintaining its moisture, had been eliminated by the intensively increased plowing. The drought conditions caused the topsoil to grow dry and friable, and was carried away by the wind. The dusty soil aggregated in the air, forming immense dust clouds that prevented rainfall.[citation needed] It was not until the government promoted soil conservation programs that the area slowly began to rehabilitate.
