Influence of Technology-Driven Land Use Change on Extreme Precipitation

The past 70 years have seen marked changes in agricultural land use in the central United States, including a twenty-fold increase in land used for soybean production and a large decrease in land used for small grains such as oats.  This land use change was driven in part by replacement of horses with mechanized equipment and transportation, which reduced the need to produce oats for horse feed.  The same period has seen a strong shift of the central U.S. precipitation intensity spectrum toward heavier events.  We investigate connections between this technology-driven land use change and precipitation intensity using the WRF-ARW model coupled with the Community Land Model.  Crop acreages for maize, soybean, winter wheat, spring wheat, and other C3 and C4 crops were reconstructed for 1940-2010 using county-level data. The resulting crop distributions were included in land surface boundary conditions for two multi-decadal regional climate simulations, one with 1940s land use and another with 2010 land use. The change in crop distribution was found to produce a shift in the precipitation intensity spectrum. Present-day (2010) land use resulted in higher frequencies for heavier precipitation amounts and lower frequencies for light amounts compared to 1940s land use. These results suggest that replacement of horses with mechanized transport contributed to alterations in land use that ultimately influenced the precipitation regime over the central United States.