Ethanol push spurring conversion of grassland to cropland — study
Source: Amanda Peterka, E&E reporter • Posted: Friday, February 22, 2013
The conversion of 1.3 million acres of grassland into cropland between 2006 and 2011 has significant implications for the environment, including a likely reduction in bird diversity, greater flood risk and the release of carbon dioxide into the atmosphere, the study published this week in the Proceedings of the National Academy of Sciences found.
“Our results show that rates of grassland conversion to corn/soy across a significant portion of the U.S. Western Corn Belt are comparable to deforestration rates in Brazil, Malaysia and Indonesia,” wrote Christopher Wright and Michael Wimberly of South Dakota State University. “Historically, comparable grassland conversion rates have not been seen in the Corn Belt since the 1920s and 1930s, the era of rapid mechanization of U.S. agriculture.”
The duo used satellite imagery from the Agriculture Department’s National Agricultural Statistics Service to map the grassland conversion in the western Corn Belt states of North Dakota, South Dakota, Nebraska, Minnesota and Iowa.
They found that conversion to cropland mostly took place in North Dakota and South Dakota, and in many cases, the converted grasslands were near wetlands or in areas that had excessively wet conditions, which could affect migratory waterfowl and shorebird diversity as well as increase the risk of runoff.
Farmers often converted grasslands that were only marginal for crop production, the authors also found. Those include lands with high erosion potential, poor soils and less than ideal climates for corn and soybean production.
That suggests that “farmers here are willing to accept higher levels of drought risk in seeking higher cash returns from corn and soybeans,” the authors wrote. “Federal crop insurance and disaster relief programs mitigate this risk, creating incentives for converting grassland to cropland, potentially at cross purposes with other national policies intended to conserve grasslands.”
Wright and Wimberly blame corn ethanol and soy biodiesel for the push to convert grassland to cropland. The western Corn Belt is “rapidly moving down the corn ethanol and soy biodiesel pathway,” they wrote. Both ethanol and biodiesel have greatly expanded since 2007, when the renewable fuel standard was revised to its current levels.
The rate of conversion has been so rapid and the reductions in soil carbon capture so great that it would take more than three decades of substituting biofuels for fossil fuels to repay, according to the study. Cellulosic biofuels, or those made from inputs other than corn starch, may be able to play a role, but it may be too little, too late, it says.
“The maintenance of mixed-grass prairie as pasture, or possible harvest of mixed-grass prairie as a cellulosic biofuel feedstock, is clearly a preferable alternative to grassland conversion. However, the development of a cellulosic biofuel industry in the United States has been slow,” the authors wrote. “The present study indicates that the window of opportunity for realizing benefits of perennial bioenergy crops may be closing in the [western Corn Belt].”
The research has drawn harsh criticism from the ethanol industry, which yesterday argued that the results are “highly questionable” and “irrelevant” to the biofuels policy debate.
The Renewable Fuels Association slammed the authors for their use of the satellite imagery, which does not distinguish between native grasslands and lands that have been used for pasturing and haying. Wright and Wimberly lumped all grasslands in one category for purposes of the study.
The group also noted that USDA has shown, in other data sets, that total crop acreage in the studied region actually declined 2.1 percent between 2006 and 2011 and that total planted acres in 2011 were at their lowest since 1995.
Those results suggest that increases in corn and soybean took place on lands that farmers previously used to plant other crops, rather than lands that held native grass, the ethanol industry contends.
“By the authors’ own admission, this study is imprecise and relies on shaky assumptions,” said Fuels America, a coalition of biofuels, agriculture and national security interests. “Here is what we know is happening on America’s prairies: the relentless hunt for fossil fuels is having a devastating effect on land, air and water. If we are serious about protecting our natural resources, we need to address our addiction to oil and support clean alternatives like renewable fuel.”