A new University of Wisconsin-Madison study says cropland expansion in the United States as a result of the Renewable Fuel Standard, led to expanded carbon emissions from 2008 to 2012, resulting in about 115 million tons of releases.
The study points the finger at the expansion of biofuels production leading to an expansion of cropland between 2008 and 2012, as the driver behind those emissions.
"Consequently, emissions from clearing land to accommodate biofuel production could significantly undermine the carbon savings that biofuels seek to attain (Gibbs et al. 2008, Elshout et al. 2015)," the report said.
"To estimate the likely impacts of cropland expansion on natural carbon stocks and implications for biofuel efficacy, we combined high-resolution maps of newly cleared croplands with spatially explicit maps of vegetation and soil organic carbon pools. Our method, for the first time, enables us to identify specific carbon stocks effected by cropland expansion and to identify hot spots of potential C emissions."
The authors write that 87% of emissions resulted from "cropland expansion onto grasslands where soil carbon was the largest source of emitted carbon.
"Expansion onto wetlands resulted in the highest potential emissions per unit area, but represented only 2% of new cropland area. Approximately 75% of all potential total emissions from cropland expansion (2008-2012) estimated from initial vegetation and soil organic carbon stocks."
For years a variety of efforts have been made to use satellite data to determine if land use changes have occurred on wetlands and grasslands, as a result of federal biofuels policies.
Renewable Fuels Association Executive Vice President Geoff Cooper, said in a statement to DTN the authors left out critical pieces of the puzzle.
"In reality, the amount of cropland used for corn production was 3.1 million acres (3.3%) lower in 2017 than it was in 2007 when the RFS was expanded," he said.
"Meanwhile, farmers produced 16% more corn per acre this year than they did in 2007. In other words, the additional corn needed to support expansion of the ethanol industry came from increased productivity on existing cropland, not from converting native grasslands into new cropland."
Cooper said the footprint of all U.S. cropland has continued to shrink. For example, the total cropland is nearly 100 million acres, or 20% lower today than it was in 1969, according to data from the U.S. Department of Agriculture and the U.S. Environmental Protection Agency.
"Higher yields for all crops mean less land is needed to meet demand," he said. "Even EPA has acknowledged this fact, recently presenting an analysis that showed U.S. crop production is up 18% since 2000, but harvested cropland is unchanged.
"Recent studies from USDA, Iowa State University, Purdue University, the Department of Energy, and others prove that land use change has been grossly overstated. Actual empirical evidence shows that farmers have responded to increased corn demand by using existing cropland more efficiently. In fact, the USDA study found that average corn ethanol reduces GHG emissions by 43% compared to gasoline, even when hypothetical land use change emissions are included.
"The authors would be well served to step outside of the ivory towers of academia and the halls of K Street lobby shops and talk with real farmers, who understand better than anyone that conserving and improving our natural resources is in the best interest of both the agriculture industry and the American consumer."
Todd Neeley can be reached at firstname.lastname@example.org
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