REVISITING THE DUST BOWL: EVALUATING NATURAL VERSUS ANTHROPOGENIC DUST SOURCES (Invited Presentation)

The 1930s Dust Bowl Drought (DBD) produced enormous dust storms, with the source of dust primarily attributed to barren agricultural fields. Recent research from luminescence dating has documented dune reactivation during the 1930s, and aerial photographs from the same time have revealed many areas of reactivated dunes, suggesting natural and anthropogenic dust sources. These observations are consistent with a historical reanalysis which documents that < 30% of the Dust Bowl area was cultivated, with a larger percentage fallow. We used the PI-SWERL (Portable in situ Wind Erosion Lab) to measure dust emission potential on a variety of soil types in the core DBD area located in Kansas, Colorado, and pan handle areas of Oklahoma and Texas, where the impacts of drought and wind erosion were most severe. Soil and landscape types included eolian sand dunes and sandsheets, fluvial deposits, and loess that existed as agricultural land or native grasslands. We found that soils dominated by eolian sand had the highest emission potential, followed by loess and fluvial sediments that were commonly crusted. Disturbed, cultivated soils have an increased emission potential if the soil is thoroughly pulverized and lacks large clods. Clods increase surface roughness and reduce dust emissions. Eolian sand, despite having a low percentage of fines, emitted an order of magnitude more dust compared to the other soils in natural or disturbed states. While cultivated agricultural fields were undoubtedly a potent source of dust during the Dust Bowl, reactivated areas of eolian sand also contributed significantly to dust emissions. This conclusion echoes other studies that reveal eolian sand bodies are likely to be important global dust sources. Our study suggests that complex interactions between extreme drought conditions and a legacy of landuse in some areas precipitated large scale landscape denudation in the 1930s. This research also provides a snapshot of potential impacts of drought in the Southern High Plains due to a warming climate.