Wetland losses due to row crop Expansion in the Prairie Pothole Region

Background/Question/Methods

Agriculture is the greatest source of wetland loss in the Prairie Pothole Region of North and South Dakota (Dakota PPR). The purpose of this study was to determine by GIS analysis recent wetland-to-row-crop transition rates within the Dakota PPR. I used the Cropland Data Layer (CDL), a detailed land use/land cover map produced annually by the U.S. Department of Agriculture, to identify current row crop distribution in the Dakota PPR. Successive CDL layers were used to examine annual wetland loss rates between 2010 and 2012. I also compared the CDL with wetland maps prepared for the National Wetlands Inventory (NWI) and the National Land Cover Database (NLCD) to calculate wetland loss rates over time spans of 10 to 32 years (the ages of those wetland maps).

Results/Conclusions

From the 1980s to 2011, the average wetland loss rate due to row crop expansion was ~52 km²/yr. However, the wetland loss rate in the Dakota PPR greatly increased in 2011 and 2012 as corn and soybean production expanded into new lands. The area of wetland lost from 2011 to 2012 was 2,314 km², an area 3/4 of the size of Rhode Island. Most of that wetland had been farmed at some point in the previous six years of CDL record, but 415 km² of the loss had not previously been row crops. Demand for corn ethanol, expiration of agricultural conservation contracts, increasing commodity prices, and drought conditions will likely continue to spur the conversion of wetlands to row crops in the Dakota PPR.