Land conversion for crops drives climate change — study
Source: Marc Heller, E&E News reporter • Posted: Friday, November 17, 2017
Researchers at the University of Wisconsin said that Northeastern states contributed more greenhouse gases per acre of converted land than Farm Belt states, and that New York now joins the ranks of the Dakotas, Texas and Kansas in leading the nation in planet-warming emissions tied to land conversion.
In a study that updates their earlier work on land conversion and renewable fuels, the researchers said that in states like New York, land is often converted from rich carbon-absorbing environments such as forests and wetlands. That means farmers release more carbon for every acre they clear for crops, although the amount of land converted is greater in the Plains states.
“While cropland expansion was most prevalent in Corn Belt and Great Plains states, we were surprised to find that the highest amounts of carbon emitted per acre of lost habitat took place in New England, states along the Eastern Seaboard, and along the upper Great Lakes,” said Tyler Lark, a co-author of the report, released by the National Wildlife Federation.
The researchers found that cropland expansion likely resulted in carbon emissions of 30 teragrams per year from 2008 to 2012. A teragram is 1 billion kilograms. Six states — North Dakota, South Dakota, Minnesota, Michigan, Wisconsin and New York — accounted for more than 35 percent of total annual emissions from cropland expansion.
Suspected ties between renewable fuels and climate change are a point of sharp debate. The NWF cited the study in calling for changes to the federal renewable fuel standard, including reducing the reliance on corn as a feedstock and developing a more accurate way for U.S. EPA to track land-use changes associated with the RFS.
The RFS disallows the conversion of uncultivated land for biofuels, but EPA tracks only aggregate changes in land use across the country, making localized information hard to come by. Congress passed the RFS in 2005 and updated it two years later.
The latest research provides “irrefutable evidence” of the unintended consequences of the RFS, said Collin O’Mara, NWF’s president and CEO, in a conference call with reporters.
Renewable fuel advocates say that evidence of a link between ethanol and big-scale land conversion is nonexistent and that much of the land that researchers suggest has been converted for corn and soybeans was simply switched from other crops or had been cropped years ago and was recently put back into production.
“The authors continue to abuse and misrepresent unreliable satellite data, and they continue to present highly uncertain modeling results as if they were the gospel truth,” Geoff Cooper, executive vice president of the Renewable Fuels Association (RFA), said in a statement. “While the new study might make for a sensational headline, the facts on the ground tell a much different story about agricultural land use and the impacts of the Renewable Fuel Standard.”
The RFA said the total amount of land used for corn in the United States has shrunk by 3.3 percent, or about 3.1 million acres, since 2007, meaning farmers are boosting corn production by being more efficient on existing cropland. In addition, total cropland is about 20 percent less than in 1969, the RFA said, citing statistics from EPA and the Department of Agriculture.
In addition, Cooper said, USDA has found that corn ethanol reduces greenhouse gas emissions by 43 percent compared with gasoline, including hypothetical effects of land-use change.
“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,” Cooper said, although the RFA has itself paid lobbyists $607,762 this year to advocate for biofuels, according to the Center for Responsive Politics.
Lark, one of the authors, said researchers relied on ground-based observations from USDA and examined tracts that had been grassland for at least a decade, in order to avoid being misled by routine crop rotations. Some of those tracts could have been coming out of the Conservation Reserve Program, he said, the program that pays farmers to leave land unplanted for periods of 10 or 15 years.
Lark said his team is updating its work to include more recent information on land use. EPA, meanwhile, faces pressure from ethanol critics to release a report on the effect of the RFS on land use, which the renewable fuel law requires every three years. The last one was in 2011.
Rep. Peter Welch (D-Vt.), who has led that effort, signed onto a letter Nov. 1 to EPA Administrator Scott Pruitt, saying the RFS has hurt the environment, among other complaints.