In Washington, a recent study (Wright et al.) funded in part by the National Wildlife Federation (NWF) suggests that significant cropland expansion occurred in areas near ethanol plants between 2008 and 2012, purportedly replacing grassland and other wildlife habitat. The study’s findings are at odds with data from the U.S. Department of Agriculture (USDA), which show U.S. cropland continues to shrink, the Renewable Fuels Association says.
However, the NWF study argues that the national aggregate trend toward less cropland hides “pockets of [land] conversion” occurring near ethanol plants. To test the validity of this assertion, the RFA disaggregated the USDA national cropland data and examined historical trends for all 180 individual counties where at least one grain ethanol plant was located in 2016. Key findings from our analysis include:
Consistent with the national trend, cropland in counties surrounding ethanol plants generally fell between 1997 and 2012. In total, cropland in the counties with ethanol plants fell by 2.02 million acres, or 3.5 percent, between 1997 and 2012.
Between 2007 and 2012 specifically (i.e., encompassing the period examined by the NWF study), total cropland in counties with ethanol plants fell by 454,000 acres, or 0.8 percent.
On an individual county basis, 2012 cropland levels were below the levels recorded in 1997, 2002, or 2007 in the overwhelming majority (84 percent) of the counties with ethanol plants.
The reduction in cropland for these 151 counties averaged 11.8 percent when compared to the highest level of cropland from 1997, 2002, or 2007. This greatly undermines the NWF study’s assertion that cropland has significantly expanded in areas near ethanol plants.
For the small minority (16 percent) of counties with ethanol plants where 2012 cropland was higher than the amount of cropland recorded in 1997, 2002, or 2007, the increase in cropland was minor (3.1 percent on average) and coincided with reductions in Conservation Reserve Program (CRP) land and pastureland.
Most of the counties with ethanol plants where 2012 cropland exceeded 1997, 2002, or 2007 levels are located in the heart of the Corn Belt, not the western fringe. This provides support for the argument that expanded cropland in these counties replaced land with previous agricultural history (such as CRP or pasture)—not prairie or other native lands.
The major differences in the findings of our analysis and the Wright et al. study are primarily explained by flaws in their data and methodology. Specifically, they relied on error-prone satellite data, compared land use from only two points in time, and classified certain croplands (e.g., idle pasture and hay) as “grassland.”
In contrast, the RFA analysis relies on land use data mandatorily reported to USDA by farmers and examines four points in time over a longer period.
The significant disagreement between USDA county-level data and the satellite data used by Wright et al. raises important questions and concerns about the validity of the NWF study’s findings, as well as the reliability of USDA satellite data for land use change analysis