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Drought Follows the Plow
| Article
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13622 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
4 / 1988 |
2,337 Words |
| Author
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Michael H. Glantz
Michael H. Glantz is head of the Environmental and
Societal Impacts Group at the National Center for Atmospheric
Research (NCAR) in Boulder, Colorado. |
Almost a century ago the belief that "rain follows the plow" was a popular one that accelerated population movements into the region now known as the American Great Plains. Until the mid-1800s, this region was considered a wasteland, useless for agriculture and human settlement, an inhospitable obstacle to settlers in search of the promised land in the western part of the North American continent.
At the same time that settlements crept westward after the Civil War in the 1860s, rainfall became more prevalent. Suddenly, what had previously been considered a barren waste was seen as a potential garden and a breadbasket for the eastern part of the country. Many attributed the increased rainfall to the effects of human settling activities, which included plowing fields, creating ponds, irrigating dry areas, and planting trees on what essentially had been a treeless grassland. The railroad companies and land speculators seized on this explanation to convince easterners to move to the Midwest. The advertising campaigns successfully produced waves of immigrants who came to the sparsely populated plains seeking their fortunes.
During the 1890s a severe, multiyear drought dispelled the rain-follows-the-plow theory. Thousands of settlers abandoned their homesteads to seek livelihoods elsewhere. It seemed that much of the support for the assumption of a causal relationship between rain and population was simply exaggeration by the railroads and other land speculators, intent on selling land at higher prices than it was worth. Before long, people realized that dry and wet periods commonly alternated and that the region's first surge of settlers had accidentally coincided with the onset of a lengthy wet spell. With the return of a prolonged drought, the credibility surrounding the rain-follows-the-plow theory itself evaporated.
The scientific reasoning behind the belief is that a region's atmospheric circulation is positively affected by increased sources of evaporation. These derive from breaking the ground with the plow, creating open bodies of water (ponds and tanks), and planting trees whose roots suck the scarce moisture from the ground and whose leaves allow the water to evaporate into the atmosphere, which ultimately returns the moisture as rain.
Today the scientific literature is still filled with articles and studies on how land use has either brought about or eliminated rainfall in a region. The belief in the rain-follows-the-plow concept still lives, although the number of its supporters appears to be small. The latest
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