APPENDIX 2. Land Use Case Study: The Dust Bowl.

As soon as the Dust Bowl began in the early 1930s, observers asked why it happened when and where it did and what caused it. Government bureaucrats quickly provided answers. The Dust Bowl was caused, they said, by the recent arrival of farmers on the southern plains. Settlers had plowed land unsuitable to crop farming, exposing bare soils to high winds. When the 1930s drought arrived dust storms drove miserable people from their homes. Almost immediately the U.S. government set out to reform land use in order to stop the dust storms and to prevent their recurrence (Hurt 1981, Worster 1979).

In the decades since the 1930s scientists have explored the physics of wind erosion. Field and wind tunnel research established the basic parameters of when and how soils erode. William S. Chepil’s wind erosion equation (WEQ) identifies five factors that contribute to blowing soils: climatic forces (precipitation, temperature, wind), soil texture, surface roughness, length of field, and quantity of vegetation. By specifying these parameters it is possible to measure and predict wind erodibility. These studies have focused narrowly within the realm of crop agriculture; the WEQ refers specifically to plowed fields. Scientists, assuming that cultivation was the primary cause of dust storms, focused their attention on how farmers should alter land use practices to avoid or diminish the incidence of wind erosion. For example, farmers can plow furrows perpendicular to prevailing winds, rather than parallel to them. They can corrugate their fields by plowing steeper furrows to increase surface roughness. And they can break up long stretches of bare soil with intermittent grass strips (Argabright 1991, Bisal and Hsieh 1966, Lyles and Allison 1976, Woodruff and Siddoway 1965).

This branch of land use and landscape science yielded worthwhile results. But without a broader historical understanding of dust storm dynamics it may be too limited. Historians, for their part, have addressed similar questions. Why did the dust storms happen when and where they did, and what caused them? In the decades after the 1930s historians traced in considerable detail the history of agricultural settlement and land use change on the southern plains between 1870 and 1935. It is clear that in the 30 years before the Dust Bowl farmers plowed a considerable amount of new land for crops (Worster 1979). But there is other historical evidence that does not fit the standard narrative. Carefully drawn maps of the erosion region held in the National Archives indicate that dust storms also happened in places with little cropland, where more than 90 percent of land area remained in native grassland cover (Cunfer 2002, Cunfer 2005). Laborious research in nineteenth century newspapers reveals that repeated, intense dust storms occurred routinely before 1900, when very little of the plains had yet been plowed for crops (Malin 1946). Archeological excavations of Native American occupation of the southern plains show that cultural occupations spanning thousands of years are often separated by deep deposits of wind-blown soils. It appears that dust storms were not a new phenomenon in the 1930s nor were they restricted to high cropping areas. Perhaps dust storms are a routine part of southern plains ecology that arise whenever and wherever there are deep and extended droughts.

The plains have experienced repeated episodes of dust storms over thousands of years. Settlement between 1900 and 1930 put farmers in the path of the next cycle of drought and wind erosion. It is unclear to what extent land use practices may have exacerbated the severity and duration of the Dust Bowl, but the story of causation is more complex than we once thought. The mechanisms of soil erosion in native grassland also remain unexplored. A combination of ecological and socio-economic research can provide a broader and fuller understanding of agroecosystems. Without scientific studies historians may misunderstand the mechanisms of wind erosion. Without historical studies to provide broader temporal and geographic contexts scientists may focus their research too narrowly on cropped fields only. Brought together a LTSER approach can provide broader understanding of human-managed ecosystems that, after all, cover the majority of the earth’s land surface.

References

Argabright, M. S. 1991. Evolution in Use and Development of the Wind Erosion Equation. Journal of Soil and Water Conservation 46:104-105.

Bisal, F. and J. Hsieh. 1966. Influence of Moisture on Erodibility of Soil by Wind. Soil Science 102:143-146.

Cunfer, G. 2002. Causes of the Dust Bowl. in Past Time, Past Place: GIS for History. ESRI Press, Redlands, CA.

Cunfer, G. 2005. On the Great Plains: Agriculture and Environment. Texas A&M University Press, College Station.

Gutmann, M. P. and G. Cunfer. 1999. A New Look at the Causes of the Dust Bowl. International Center for Arid and Semiarid Land Studies, Lubbock, TX.

Hurt, R. D. 1981. The Dust Bowl: An Agricultural and Social History. Nelson-Hall, Chicago.

Lyles, B. E. and L. Allison. 1976. Wind Erosion: The Protective Role of Simulated Standing Stubble. Transactions of the American Society of Agricultural Engineers 19:61-64.

Malin, J. 1946. Dust Storms, 1850-1900. Kansas Historical Quarterly 14:129-144,265-297,391-413.

Woodruff, N.P and F.H. Siddoway. 1965. A Wind Erosion Equation. Soil Science Society of America Proceedings 29:602-608.

Worster, D. 1979. Dust Bowl: The Southern Plains in the 1930s. Oxford University Press, New York.