Use of the Cropland Data Layer to monitor grassland conversion in the U.S. Western Corn Belt (Invited)

The U.S. Department of Agriculture's Cropland Data Layer (CDL) provides new opportunities for monitoring land cover/land use change (LCLUC) related to U.S. agricultural policy, bioenergy development, and recent commodity price increases. We used the CDL to assess the conversion of grasslands to corn/soy cultivation along the western periphery of the U.S. Corn Belt. Here, we find rapid grassland conversion (1-5% annually) as the Corn Belt expands westward and northward into North Dakota and South Dakota. This LCLUC is occurring in close proximity to wetlands in the Prairie Pothole Region. In most counties in the eastern Dakotas, grassland conversion exceeds declines in land area enrolled in the Conservation Reserve Program (CRP). Within the core corn/soy growing area in Iowa and southern Minnesota, LCLUC is occurring on marginal lands characterized by high erosion potential and less-productive soils. In Minnesota, particularly, corn/soy production is increasing on lands previously too wet to farm without an expansion of agricultural drainage practices. Over the period 2006-2011, we estimate a net greenhouse gas impact of grassland conversion in the Western Corn Belt of approximately 4*106 metric tons CO2-equivalent. Although not designed for monitoring grasslands, we suggest that the CDL can be used judiciously to identify grassland conversion at farm- to sub-county scales, and, in conjunction with other national-level datasets (e.g., the National Wetlands Inventory and SSURGO database), to provide timely feedback to policymakers and the public on likely environmental impacts of U.S. agricultural policies and shifting market forces.