Response to “Recent Land Use Change in the Western Corn Belt Threatens Grasslands and Wetlands”
A recently published study by C.K. Wright & M.C. Wimberly in the Proceedings of the National Academies of Science suggests that native grasslands in Iowa, Minnesota, Nebraska, North Dakota, and South Dakota have been converted to cropland to facilitate increased corn and soybean plantings between 2006 and 2011. The study's findings stand in stark contrast to U.S. Department of Agriculture (USDA) acreage data, which show increased corn and soybean acres in the region have occurred via crop switching, not cropland expansion. Further, the extremely high rate of error associated with the satellite imagery used by the authors renders the study's conclusions highly questionable and irrelevant to the biofuels policy debate.
Readers of the recent PNAS paper should give strong consideration to the following points:
- Current law strictly prohibits the conversion of sensitive ecosystems to cropland. At least once a year, farmers must certify that they are complying with the highly erodible land conservation and wetland conservation requirements (the so-called "sodbuster" and "swampbuster" provisions) of the Farm Bill. Most producers strictly adhere to conservation plans that are often developed with technical assistance from the Natural Resources Conservation Service.
- Further, the provisions of the Energy Independence and Security Act require that corn and other feedstocks used to produce biofuels for the Renewable Fuel Standard (RFS) may only be sourced from land that was actively engaged in agricultural production in 2007, the year of the bill's enactment. Feedstock from lands converted to cropland after 2007 would not qualify for the RFS, and thus the program strongly discourages cropland expansion.
- The study's authors themselves acknowledge that the converted lands they classify as "native grasslands" might actually have been land planted to hay, grass pasture, or idled cropland enrolled in the CRP program. They write, "One shortcoming of the present study was our inability to...distinguish between different types of grassland conversion, i.e. to separate native prairie conversion from change involving CRP, hay lands, or grass pasture." Thus, the authors' conclusion that increased corn and soybean acres are coming at the expense of "native prairie" is highly suspect. In fact, USDA data shows decreased hay acres in the region, strongly suggesting that much of the increase in corn and soybean acres came on land previously planted to hay. At the same time, CRP enrollments in the region have declined slightly, suggesting that farmers are bringing some idled cropland back into production.
- Data from USDA show that the increase in corn and soybean acres in the five-state region was primarily achieved via crop switching rather than cropland expansion. That is, farmers increased corn/soybean plantings on land previously planted to hay, wheat, and other crops. Indeed, USDA shows total crop acres in the five-state region actually declined 2.1% from 2006 to 2011.
(Note: Total crop acres include planted acres for corn, sorghum, oats, barley, rye, winter wheat, Durum wheat, other spring wheat, rice, soybeans, peanuts, sunflower, cotton, dry edible beans, potatoes, sugarbeets, canola, proso millet, and harvested acres for all hay, tobacco, and sugarcane).
- In fact, total planted cropland in the five states in 2011 was the lowest since 1995. Total planted acres in 2011 for the five-state area were 3.6% below the 10-year average (2001-2010).
- While North Dakota planted 540,000 more acres to corn in 2011 than in 2006, total acres planted to all crops in the state actually fell 3.25 million acres (15%) between 2006 and 2011. Total planted crop acres in 2011 were also lower in Minnesota. This strongly suggests the expansion in corn area took place on land previously planted to other crops.
- While a useful tool for analyzing potential trends, the USDA Cropland Data Layer (CDL) system utilized by the authors to estimate land conversions has demonstrated a high level or error in differentiating between grasslands and land planted to hay and other crops. USDA itself acknowledges that, "Unfortunately, the grassland-related categories have traditionally had very low classification accuracy in the CDL." For example, USDA accuracy data shows the CDL tool mischaracterized North Dakota acreage for alfalfa, other hay, and idle/fallow cropland more than half the time in 2012.
When the facts are on the table, it becomes clear that readers of the new PNAS study should exercise great caution and skepticism when interpreting the authors' conclusions. After all, as eloquently stated by Meade County (South Dakota) Farm Service Agency director James R. Neill, "...farmers and ranchers are the best conservationists in the world as they have a vested interest in conserving the agricultural resources for today and future generations."