The 1930's Dust Bowl Drought

Dust Cloud
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The Dust Bowl was not only one of the worst droughts in United States history, but is generally thought of as the worst and most prolonged disaster in American history.

The effects of the "Dust Bowl" drought devastated the United States central states region known as the Great Plains (or High Plains). At the same time, the climatic effects all but dried up an already depressed American economy in the 1930's creating millions of dollars in damages.

A Region Already Prone to Drought

The Plains region of the United States has a semi-arid, or steppe climate. The next driest to desert climates, semi-arid climates receive less than 20 inches (510 mm) of rainfall per year which makes drought a serious weather hazard. 

The plains are a broad expanse of flat land positioned to the east of the Rocky Mountains. Air flows down the lee slope of the mountains, then warms and rushes out across the flat land. Although there are periods of average or above average rainfall, they alternate with periods of below average rainfall, creating episodic, recurrent drought. 

"The Rain Follows the Plow"

Known as the "Great American Desert" to early European and American explorers, the Great Plains was first thought to be unsuitable for pioneer settlement and agriculture thanks to the lack of surface water. 

Unfortunately, an unusually wet period in the second half of the 19th century gave rise to the pseudoscience theory that establishing farming would bring about a permanent increase in rainfall. Some researchers promoted "dryland farming," such as the "Campbell method," which combined subsurface packing–the creation of a hard layer about 4 inches below the surface—and "soil mulch"–a layer of loose soil at the surface. 

Farmers began using the Campbell method to conduct large scale farming in the 1910s and 1920s, while the climate was somewhat wetter. When the drought hit in the late 20s, though, the farmers didn't have enough experience to have learned what the best tillage practices and equipment would be best for the steppe lands. 

Heavy Debt Load 

In the late 1910s, prices for wheat, the main Dust Bowl crop, were quite high due to demands for feeding people during World War I. Farmers used emerging tractor technologies to work the land and although tractors lowered labor costs and allowed the farmers to work larger acreages of land, the higher capital costs required for tractors resulted in mortgages on farms. The Federal government became involved in farm credit during the 1910s, making mortgages easier to obtain. 

But in the 1920s, crop prices dropped as production increased, and reached minimum levels after the crash of the economy in 1929. Low crop prices were paired with poor harvests due to the drought but exacerbated by infestations of rabbits and grasshoppers. When all those conditions came together, many farmers had no choice but to declare bankruptcy.

Drought 

A research study in 2004 by NASA senior research scientist Siegfried Schubert and colleagues found that precipitation in the Great Plains is sensitive to global sea surface temperatures (SSTs) which varied at the time. American research meteorologist Martin Hoerling and colleagues at NOAA suggest instead that the main reason for the drop in rainfall for the region between 1932 and 1939 was triggered by random atmospheric variability. But whatever the cause of the drought, the ending of the wetter period in the plains between 1930 and 1940 couldn't have come at a worse time. 

The prolonged drought was made much worse by a fundamental misunderstanding of high plains environment, and the utilization of methods which called for a thin layer of dust to be purposefully exposed on the surface for large parts of the summer. Dust transmits influenza virus and measles and combined with the economic depression, the Dust Bowl period brought a significant increase in the number of measles cases, respiratory disorders and increased infant and overall mortality in the plains. 

Sources and Further Reading