Oceanography in the 21st Century - An Online Textbook
navigation bar for the online textbook

 

The Dust Bowl and Aftermath

Degraded land, stripped of its vegetation, trodden by the hooves of cattle or goats, overturned by the plow, turns to dust and blows away, creating local and global problems. Today, vast regions of Mongolia are blowing away, creating dust storms that blanket Beijing, cross the Pacific, and drop dust on North America. In the 1930s, the dust bowl of North America destroyed farmland, triggered a mass migration out of the great plains, and led to new farming practices. Even now,much of the great plains remains vulnerable to desertification. Sand dunes cover most of Nebraska, held in place by thin layer of vegetation. The Texas panhandle has many seasonal lakes, playas, that can be easily eroded by wind.

The dust bowl was the result of changing weather patterns bringing drought to a region susceptible to wind erosion and denuded of vegetation by changes in land use. Let's look at the conditions leading to the dust bowl.

Geological Conditions

The great plains of North America are the western part of the great Interior Plains, the wide expanse of flat land stretching from the Mississippi River to the Rocky Mountains and from the Gulf of Mexico to northern Canada.

map of the great plains of north america
Map of the Great Plains.
From The Geological Story of the Great Plains, by Donald E. Trimble, USGS Bulletin 1493.

Just below the surface of large areas of the Great Plains are wind-deposited sand and stabilized sand dunes that can return be easily eroded by the wind when vegetation covering the dunes is destroyed.

aeolian sand deposits in great plains of North America

Climatological Conditions

The climate of the Great Plains is characterized by:

  1. Little rain. Rainfall varies from 28 inches per year (700 mm/yr) in the east to 10 inches per year (400 mm/yr) in the west. Areas with rainfall less than 28 inches (700 mm/yr) are generally classified as semi-arid. Areas with rainfall less than 15 inches (350 mm/yr) are generally classified as arid. The map below shows the Great Plains outline superposed on the map of rainfall.

    precipitation map of the united states
  2. Few rivers.
  3. High winds. The Great Planes are one of the windiest regions of the country.
  4. Cold winters with snow and blizzard conditions.
  5. Very hot summers with thunderstorms, hail, and tornados. The greatest concentration of tornados is in the Great Plains. Hot summers dry out the land, leading to wind erosion of areas without vegetation.
  6. Recurring droughts tied to changes in sea-surface temperature over large oceanic areas. Farmers are lured into dry areas during wet years, then they are unable to farm during the drought years that invariably follow the good years.

The arid and semi-arid plains are poorly suited for agriculture, especially the types of agriculture practiced by the first immigrants to the region.

We learned in the chapter on The Oceanic Influence on North American Drought that the oceans strongly influence rainfall over North America. Schubert et al used this information to reconstruct the influence of sea-surface temperature on weather patterns over North America during the major drought of the 1930s. They found that sea-surface temperature in the tropics was very important.

During the 1930s, the United States experienced one of the most devastating droughts of the past century. The drought affected almost two-thirds of the country and parts of Mexico and Canada and was infamous for the numerous dust storms that occurred in the southern Great Plains. In this study, we present model results that indicate that the drought was caused by anomalous tropical sea surface temperatures during that decade and that interactions between the atmosphere and the land surface increased its severity. We also contrast the 1930s drought with other North American droughts of the 20th century.
From On the cause of the 1930's Dust Bowl, a Science article by Schubert et al (2004).

calculated and observed rainfall over great plains 1932 to 1938

Observed precipitation in the great plains region of North America 30ªN to 50ªN, 95ªW to 105ªW (boxed area on maps) compared with precipitation calculated from an atmospheric general circulation model forced by observed sea-surface temperature data. The calculated precipitation has been smoothed to remove fluctuations with periods shorter than six years. The thin black lines are 14 different simulations. The variation shows some of the uncertainty of the calculated precipitation. The green line is the average of the 14 simulations. The maps show the anomaly of precipitation averaged from 1932 to 1938. Click on the image for a zoom.
From Schubert et al (2004).

Changes in Land Use

Originally the great plains were grasslands divided into short grass prairies in the west and long grass prairies in the east. The grasslands supported vast herds of large animals, including camels, horses, mammoths, bison, giant bison, giant beavers the size of black bears, and saber-toothed tigers. Most disappeared with the arrival of humans around 11,000 BC, leaving primarily large herds of bison. (Spaniards reintroduced the horses used by American Indians). Periodic droughts and fires kept the plains as grasslands. And the grass had a thick tangle of roots reaching deep underground to supply water in dry times, and resources to regrow after fire.

Beginning around 1840, the influx of Europeans into the Great American Desert as the Great Plains were then known, and new technology brought rapid change. Cattle barons, moving out of Texas after the Civil War, soon controlled vast herds of cattle that grew in size from 1 million in 1870 to 8 million in 1886 (Thomas et al 1997). At the same time, buffalo hunters killed most of the bison, pushing them close to extinction. Railroads pushing west after 1866 enabled cattle to be brought to market from new cities as Wichita, Kansas and Abilene, Texas. Ranching led to overgrazing in some areas, and the drought of 1883–1884, low prices for cattle, the invention of barbed wire in 1874 and the fencing of rangeland, and the blizzards of 1885–1886 led to the collapse of the cattle industry by 1890.

Cattle ranchers were replaced by farmers of European descent, leading to a rapid increase in population of the plains. Farmers were drawn to the region by a variety of factors:

  1. The steel plow, invented by John Deere in 1846, was capable of breaking the thick sod of the tall-grass prairies.
  2. The invention of the windmill gave farmers permanent access to groundwater.
  3. The introduction of the mechanical tractor and combine in the early 20th century allowed farmers to operate large farms of many acres.
  4. The introduction of winter wheat from Russia, a variety well adapted to conditions on the plains.
  5. The Homestead Act of 1862, designed to speed up the settlement of the west, gave 160 acres to settlers who would work the land for five years.
  6. Very high wheat prices during World War I further fueled the rapid expansion of farmland, followed by yet more expansion in the 1920s.
  7. Railroads and speculators published brochures touting the rich farmland waiting to be opened up, and offered one-way tickets to farmers willing to homestead on the new free lands on the plains. By 1890 six million people had arrived (Thomas et al 1997). Many were tenant farmers working for large landowners.

price of wheat adjusted for inflation 1866 to 1999
Price of wheat in US dollars, adjusted for inflation. The spike in 1918 was due to demand for wheat during WW–I, the drop in 1933 was due to the Hawley-Smoot Tariff Act, the peak in 1944 was again due to world war, and the peak in 1974 was due to large imports by the Soviet Union. The overall downward trend since 1940 is due to more efficient farming practices, new strains of wheat, and irrigation. Note: These prices are approximate. There were many markets selling wheat at different prices, and the influence of inflation was different for different crops and goods. See the Historical Statistics site for more information.
From Historical Statistics of The United States: Wheat, spring wheat, and winter wheat–acreage, production, price, and stocks: 1866–1999.

The new farmers raised crops using methods suitable for Europe and the eastern United States, but these farming methods led to disaster on the Great Plains. They plowed deeply to eliminate weeds and grasses, planted crops, harvested the crops, and left their fields bare until the next growing season, although frequent plowing reduced soil moisture, broke up clods, and produced a layer of dust at the surface, all of which facilitated wind erosion. They tended to raise wheat because Russian wheat grew well, it brought high prices, and it was easy to grow and harvest using mechanical equipment.

Collapse of Farming and the Dust Bowl

The widespread plowing of the plains beginning in the early 20th century destroyed the original short-grass prairie, replacing it with wheat fields.The collapse of wheat prices after World War I pushed farmers to further expand acreage devoted to wheat in a futile attempt to raise their income. Then the Hawley–Smoot Act Tariff Act of 1930 was passed by Congress in a disastrous attempt to stem the financial crisis of 1929 by reducing the import of foreign goods and crops. This led to retaliatory tariffs which greatly reduced the export of American wheat, driving wheat prices to historic lows and forcing farmers throughout the Great Plains into bankruptcy. Prices fell from $70/ton during World War I to $35/ton in 1929 to $7/ton in 1931 (Thomas et al 1997).

When drought began in the early 1930s, the wheat failed to sprout, leaving bare, plowed fields at the mercy of the strong winds sweeping across the plains. Vast dust storms followed, destroying farms and driving 50,000 people a month from the land at the height of the Dust Bowl.More than 300,000 rural people left the plains for California. Their story was told eloquently by John Steinbeck in Grapes of Wrath published in 1939.

Grapes of Wrath book cover
Grapes of Wrath book cover.
From Syracuse Library Special Collections Research Center Exhibition on Steinbeck's Grapes of Wrath: Bitter Fruit of the Great Depression.

Buried machinery in Dallas, North Dakopta during the dust bowl
Buried machinery in barn lot in Dallas, South Dakota, United States on 13 May 1936 during the Dust Bowl. Click on the image for a zoom.
From United States Department of Agriculture; Image Number: 00di0971from WikiMedia Commons.

25 million hectares of land were eroded by the wind by 1936. Some topsoil was deposited as far as Washington DC and 2000 kilometers out over the north Atlantic (Thomas).

Lessons Learned

The dust bowl led to the establishment of the Soil Conservation Service that drew on engineers, agronomists, and range management experts to develop best farming practices for the Great Plains. They recommended (National Resources Conservation Service: Conserving the Plains: The Soil Conservation Service in the Great Plains):

  1. Use of contour plowing, strip cropping, erosion control dams, and other measures to reduce runoff of rain and increase the retention of water,

    strip crops and contour plowing reduce soil erosion and rapid runoff of rain water.
    Strip crops and contour plowing reduce soil erosion and rapid runoff of rain water.
    From Oregon State University. New concepts could change face of America's cornbelt.

  2. Use of strips of vegetation and trees to slow the wind,
  3. Leave crop residues on the surface, and use stubble mulching and minimal tillage to reduce erosion,

    stubble mulching to reduce soil erosion
    Stubble mulching to reduce soil erosion.
    From Kelly Engineering.

  4. Conversion of the most easily eroded land from farming to ranching based on good range management,
  5. Eliminate overgrazing, rotate cattle through pastures, apply ecological concepts to range management,
  6. Use federal subsidies, crop insurance programs, and allotments to discourage farming unsuitable drylands.

Initially, farmers employed these soil conservation measures. But above normal rainfall in the 1940s and record high wheat prices during World War II led to the expansion of wheat farming into unsuitable area, and soil conservation methods were abandoned. Drought returned to the great plains from 1950-1956 causing further damage, dust storms, and soil erosion. In 1956, in an effort to reduce future damage, the US Department of Agriculture began the Soil Bank Program that paid farmers to remove marginal drylands from cultivation. Some lands were planted in trees. In 1956, soon after the program started, 500,000 farmers agreed to take 10,720,749 acres out of production. By 1960, 28.7 million acres were in the soil bank.

The results of good (and poor) soil conservation practices are readily seen today in many parts of the Great Plains.

over grazing in drought years in great plains leads to destruction of vegetation holding soil in place
Grassland management needs to involve grazing. Fall scene of season-long grazing at the end of one of the driest years on record in the Sandhills of Nebraska. Plants will be in an extreme weakened condition to begin plant growth next spring.
From Water: Sandhills' Greatest Resource.

grasslands at end of drought year with controlled grazing.
Pasture scene from the Sandhills of Nebraska taken in the late summer of one of the driest years on record. The grassland is part of a large herd, short duration system.
From Water: Sandhills' Greatest Resource.

Great droughts may return to the Great Plains if earth warms due to increasing levels of carbon dioxide in the atmosphere and we return to the warmer climate of the medieval warm period.

The western United States is experiencing a severe multiyear drought that is unprecedented in some hydroclimatic records. Using gridded drought reconstructions that cover most of the western United States over the past 1200 years, we show that this drought pales in comparison to an earlier period of elevated aridity and epic drought in AD 900 to 1300, an interval broadly consistent with the Medieval Warm Period. If elevated aridity in the western United States is a natural response to climate warming, then any trend toward warmer temperatures in the future could lead to a serious long-term increase in aridity over western North America.
From Long-Term Aridity Changes in the Western United States by Cook et al (2004).

Dust Storms In Central Asia

Spring dust storms have become common in China, increasing from one in three years in the 1940s to 18 in 2001. The sand storms originate in the arid areas of southern Mongolia and northern China, and they carry dust across eastern China, Japan, the Pacific, and North America. In May 2007, dust from one storm was tracked as it circled the earth three times before dissipating. They result from land degradation due to over grazing in the arid areas. Today's conditions in Mongolia are reminiscent of conditions leading up to the dust bowl.

  1. Large flat areas underlain by sand and loess deposits easily eroded by the wind.
  2. High winds.
  3. Little rain. 2 inches/year (50 mm/yr) in the Gobi Desert in the south to 20 inches/year (500 mm/yr) in the north.
  4. Extreme range of temperature with a 50ªC range in average temperatures from winter to summer.
  5. Few rivers. Most precipitation evaporates, 6% runs off, 3% percolates into the ground.
  6. Land degradation.
    1. The population has tripled since 1960, increasing from 0.9 million in 1960 to 2.8 million in 2005.
    2. Mongolia changed from a free, nomadic society to a centralized, collective society in the 1920s. Then changed back to a somewhat free nomadic society in the 1990s. But the old ways had been mostly forgotten. Too many people raising too many animals without traditional knowledge of the country's ecology, and without traditional controls of herding, led to land degradation. The old traditions of the "commons" had been lost in the 70 years since the 1920s, leading to a true "tragedy of the commons" in the 1990s.

      In Mongolia, private property in pastureland has never existed, and privatization of pasture remains unconstitutional. Rather, there existed a complex of distinct but often overlapping or nested tenures to a variety of resources vested in groups of different sizes and social functions and governed by an array of formal and informal institutions. These pastoral resources included seasonal pastures (winter, spring, summer and autumn), natural and man-made water sources, campsites, animal shelters and corrals, hay-cutting grounds, salt licks, and stock driveways. Prior to Mongolia’s communist revolution in 1921, pasture allocation and use were governed in many areas by a combination of formal regulation imposed by ruling nobles (either secular princes or high-ranking lamas in the Tibetan Buddhist church), and informal norms and customs described by herders as “unwritten law.” During the last thirty years of socialist government (1960-1990), pasture use was regulated by the state, through the mechanism of the negdel or collective, although customary patterns of use and tenure informed negdel decisions to varying degrees. Since the demise of socialism in Mongolia (1990), and the difficult emergence of a market economy and democratic political system, pasture use has not been formally controlled. The collectives that once allocated pastures and campsites and directed seasonal movement patterns were dismantled in 1992 and state-owned livestock were privatized.

      Fernandez-Gimenez (2000).

    3. As a result of political changes in the 1990s, native grasslands are being over grazed and destroyed.
    4. Demand for agricultural products has led to conversion of pasture to farmland with spring tilling coinciding with the season of highest winds.
  7. Drought. Severe droughts have recently become more common after decades of slightly increasing drought index values since 1940 (Batima et al 2007). The latest droughts were in 1999–2002 (the worst in 60 years) and 2008 (the driest since 1951 in north China and Inner Mongolia).

duststorm in Taklimakan Deert
Terra satellite captured this image of a dust storm over the Taklimakan Desert, in western China on April 7, 2004.
From Dangerous Dust Storms on The Rise.

Additional Reading

You can learn much more about the great plains at the US Diplomatic Mission to Germany's web site on the geography of the western US. Donald Trimble has a good introduction to the geology of the great plains.

The American documentary films The Plow That Broke the Plains and The River (1936) originally produced by the US Government Resettlement Administration, describe environmental problems culminating in the Dust Bowl, and the great floods of the Mississippi River in the 1930s. The films won many prizes and pioneered new filmmaking techniques. Available on Google Video.

References

Fernandez-Gimenez, Maria E., and B Batbuyan. 2000. Law and Disorder in Mongolia: Local Implementation of Mongolia's Land Law. Presented at "Constituting the Commons: Crafting Sustainable Commons in the New Millenium", the Eighth Conference of the International Association for the Study of Common Property, Bloomington, Indiana, USA, May 31-June 4. Digital Library of the Commons.

Punsalmaa Batima, Luvsan Natsagdor, and Nyamsurengyn Batnasan. 2007. Vulnerability of Mongolia's pastoralists to climate extremes and changes. In: Climate Change and Vulnerability. Edited by Neil Leary, Cecelia Conde, Jyoti Kulkarni, Anthony Nyong, Juan Pulhin. Earth scan Publications Ltd: 68–87.

Schubert, S. D., M. J. Suarez, et al. (2004). On the Cause of the 1930s Dust Bowl. Science 303 (5665): 1855–1859.
During the 1930s, the United States experienced one of the most devastating droughts of the past century. The drought affected almost two-thirds of the country and parts of Mexico and Canada and was infamous for the numerous dust storms that occurred in the southern Great Plains. In this study, we present model results that indicate that the drought was caused by anomalous tropical sea surface temperatures during that decade and that interactions between the atmosphere and the land surface increased its severity. We also contrast the 1930s drought with other North American droughts of the 20th century.

Thomas, Squires, and Glenn (1997) The North American Dust Bowl and Desertification. In: Middleton and Thomas (eds) World Atlas of Desertification 149–154.

Revised on: 24 July, 2009

navigation bar for the online textbook
Copyright and contact information for Our Ocean Planet
click here to get back to the table of contents click here to get back to the send an email to the person who designed this web page click here to send an email to the author click here to get back to the course schedule page click here to the table of contents click here to go back to the home page of oceanworld