Estimating the Location of Undisturbed Lands Using the USDA Cropland Data Layer.

Undisturbed lands that have never been plowed are more highly valued for conservation, but few maps exist showing their location. The US Department of Agriculture’s (USDA) Cropland Data Layer (CDL) shows non-cropland, but does not distinguish native prairie from other types of non-cropland. Our objective was to evaluate a multi-date (2006-2012) stack of CDL natural lands as a proxy undisturbed land map, using as ground truth an undisturbed lands map independently prepared for the Prairie Coteau Region of eastern South Dakota by visually interpreting digital aerial photos. The undisturbed lands map also used proprietary crop history data from 1950-2012 from the USDA’s Common Land Units crop data layer to define areas that are most likely undisturbed. For comparison, we used the CDL to define "natural" areas as those with forest, grassland, open water, wetland, pasture, or non-alfalfa hay, and then stacked the layers for 2006-2012 to identify continuously natural lands. Of the 21,987 km² study area, the CDL stack captured 79% of the undisturbed lands. Where the CDL stack did not capture undisturbed lands it was most likely to be classified as corn or soy. Identifying undisturbed lands using the CDL alone would allow estimation of undisturbed lands in regions not covered by the visual interpretation maps, and could provide a cost savings over the time-consuming visual interpretation methods if sufficiently accurate.