Geoscience Reference
In-Depth Information
Box 23.1
The Dust Bowl
The 1930s Dust Bowl in the Great Plains of the United States has become synonymous with ideas of land
exploitation. It was a result of the combined impacts of recurrent drought and excessive agricultural activity on
dryland soils, but with the additional driving force of free enterprise and an expansionary culture (Cooke and
Doornkamp, 1990). The result was 8000 ft high dust storms, 9 million hectares of damaged agricultural land,
decimated wheat harvests, massacred livestock, farm abandonment and massive social hardship (Worster, 1979).
Cook, Miller and Seager (2009) describe the resulting human migration as being comparable in the recent history
of the USA only to the evacuation of New Orleans in 2005 as a result of hurricane Katrina.
In the 1800s the drought-resistant prairie grasslands of the Great Plains, centred at the junction between Colorado,
Kansas, New Mexico, Oklahoma and Texas, were replaced with drought-sensitive wheat crops (Cook, Miller and
Seager, 2009). By the late nineteenth and early twentieth century the rate of cropland expansion was boosted by
an ever-growing number of steam- and gasoline-powered tractors. The term 'sodbusting' was coined as the land
under wheat increased by 50 % between 1925 and 1930 (Worster, 1979). After World War I the demand for wheat
was huge and the farmers responded by increasing their farm size (up to 50 square miles) and embarking on
overnight ploughing (Worster, 1979). In the 1930s the region was hit by a period of severe drought with average
precipitation reducing by more than 50 %. This period of additional environmental stress coincided with a severe
economic depression that caused the price of wheat to collapse. With no drought plan and minimal erosion control
measures many wheat farmers responded to their falling income by increasing the intensity of farming. By 1935,
33 million acres of ploughed, bare and desiccated soils were left susceptible to the wind (Worster, 1979) and the
subsequent devastating dust storms reached beyond the eastern seaboard of the US. Worster (1979) argues that
while the physical environment played a part in the catastrophe, social and economic considerations were equally
culpable. He describes the farmers as, '
...
fatalistic optimists, their eyes weren't looking at the soil, they were fixed
to the stockmarket
their solution was to plant more wheat'. With the dust clouds enveloping the New York Stock
Exchange he suggests that '
...
there was no significant difference between 'Black Thursday' on Wall Street and
the black days of the Dust Bowl'.
It could be argued that the Dust Bowl was the first time that western culture had come up against natural limits
and it inspired the first scientific investigations of land management in dryland regions. Conservation research
inspired by the Dust Bowl made it clear that agricultural activity on dryland soils required careful management to
avoid accelerating aeolian erosion, and soil conservation strategies involving windbreaks, crop management and
tillage operations were rolled out across the Great Plains. Nordstrom and Hotta (2004) describe how the Great
Plains region was hit by an even more acute drought in the 1950s and yet problems of wind erosion were less severe.
Lee, Wigner and Gregory (1993) explain this reduction in wind erosion severity in the 1950s to the successful
implementation of soil conservation measures on agricultural land. However, if such conservation strategies are
poorly applied or allowed to diminish then severe wind erosion problems are evident to this day.
...
standards for air quality for the 24 hour and annual av-
erage concentrations of such particles in order to protect
public health and to help identify particularly hazardous
dust sources.
increase in the number of daily emergency room visits for
bronchitis for each 100 µg/m
3
increase in PM
10
as a re-
sult of dust storms in Washington State. Chan
et al.
(2008)
noted that long-distance transport of desert dust in Asia
resulted in a 67 % increase in cardiopulmonary emergency
hospital visits in Taiwan when PM
10
concentrations were
above 90 µg/m
3
, with a near 5 % increase in mortality
(Chen
et al.
, 2004). Similar increases in mortality as a
result of Asian dust storms have also been recognised in
Korea (Kwon
et al.
, 2002). Recognition of the harmful ef-
fectsofPM
10
and PM
2.5
is such that the US Environmental
Protection Agency (USEPA) has, since 1986, set national
23.4
Agricultural wind erosion
Wind erosion from agricultural land in semi-arid environ-
ments is one of the major causes of human-induced aeo-
lian dust in the atmosphere. Much research on the problem
has been carried out in the west and mid-west USA where
