A new study from researchers at the University of Wisconsin-Madison shows that corn and soy, two crops commonly used for biofuels, are expanding into previously un-farmed prairie in the United States.
The study used high-resolution satellite images to identify where cropland expanded between 2008 and 2012, the four years following the passage of the Renewable Fuel Standard, which mandates the use of renewable fuels including biofuels. Of course, not all of this crop is used for biofuels, but ethanol has driven up the domestic demand for corn (see chart below). In 2014, over 40 percent of corn grown in the U.S. was used to make ethanol, according to data from the United States Department of Agriculture.
"We realized there was remarkably limited information about how croplands have expanded across the United States in recent years," said Tyler Lark, the lead author of the study, in a press statement. “Our results are surprising because they show large-scale conversion of new landscapes, which most people didn't expect."
The study found that crops commonly used for biofuels expanded by 7 million acres, and that 1.6 million acres of that was onto previously undisturbed grasslands. That’s an area of prairie about the size of Delaware.
If the goal of biofuels is to create a greener way to power transportation, converting prairies to do so is counterproductive. Grasslands are not only home to threatened plant and animal species, but they are also carbon sinks. Tilling natural grassland releases considerable carbon dioxide into the atmosphere, spurring on climate change.
In fact, soy and corn grown on newly converted farmland could be ineligible for renewable fuel production according to the rules of the Renewable Fuel Standard, which requires biofuel crops only be grown on preexisting agricultural land. The researchers found that 3.5 million acres of crops were grown on newly converted land. Yet this went undetected, due to weaknesses in the federal monitoring system.
Most of the converted land is located in the Central Plains, which stretch from North Dakota down to Texas. Much of these grasslands aren’t well-suited for biofuel crops, and are prone to problems like drought and soil eroision. “It mimics the extreme land-use change that led up to the Dust Bowl in the 1930s," said Lark.
The paper’s authors hope the research will be considered by policy makers reviewing the Renewable Fuel Standard. The findings are published in the journal Environmental Research Letters.