Hundreds of thousands of acres of grasslands and wild habitat in the Upper Midwest have been plowed up to plant corn and soybeans in the past decade because of demand created by the government's ethanol mandate, according to a trio of academic researchers who argue that federal biofuels policy is causing more environmental harm than good.

Their study, released Thursday, found that the shift has destroyed crucial habitat for monarch butterflies and increased the use of chemical fertilizers, while causing the release of millions of tons of carbon dioxide — equal to putting about 5 million more cars on the road each year.

The study was completed in response to a 2018 report by the U.S. Environmental Protection Agency (EPA) and designed to quantify exactly how much new cropland was brought into production nationally as a direct result of the ethanol mandate. The EPA report laid out much of the potential environmental damage caused by increases in row cropping, but couldn't specify how much reflected demand for ethanol and how much reflected other market factors. Several environmental groups are pressing Congress to revise federal biofuels standards in a way that moves away from corn and soy-based ethanol.

"For years we've known that agricultural lands have been changing," said Tyler Lark, associate researcher at the University of Wisconsin, one of the study's authors. "Thanks to this new research we finally know exactly how much of that additional corn and cropland is due to the Renewable Fuel Standard."

The standard, which requires refiners to blend a certain amount of gasoline with biofuels, was created in 2007 and meant to curb greenhouse gas emissions. But the production of biofuels from environmentally friendly "advanced" sources such as grasses or plant and animal waste has lagged behind what lawmakers expected more than a decade ago. Instead, biofuels have been almost entirely produced from corn and soybeans.

The study estimates that 1.6 million acres of grass and wetlands nationally were converted to grow crops because the demand for ethanol inflated the prices of corn and soybeans. Another 1.2 million acres of existing farmland, especially in the Midwest, would have been retired to pasture or conservation lands were it not for the mandate.

Add that to the millions of acres of farmland that were switched to corn from other crops and the mandate is responsible for adding about 300,000 tons of nitrogen fertilizer a year that has been draining into waterways and causing algae blooms and dead zones, the study found.

"There is no dispute that U.S. biofuels policy is driving environmental harm," said Aaron Smith, agricultural and resource economics professor at University of California-Davis, one of the authors.


The authors calculated the shift in land use by analyzing U.S. Department of Agriculture (USDA) data that tracks cultivation county by county. They then used satellite images to see exactly where within each county the land had changed, Lark said.

Biofuel supporters and some other researchers have faulted this use of satellite imagery, saying it is often inaccurate. They also say it's hard to tell if new land is being plowed or if fields are just going through normal crop rotation patterns.

Ashwin Raman, a spokesman for the Minnesota Bio-Fuels Association, said the group hasn't had a chance to review the new study specifically but has challenged Lark's past research.

"This seems to happen every now and then, but when we go in and look at the actual acreage from the USDA, it shows it's not as severe as it's being portrayed by some of these groups," Raman said.

Raman pointed to a 2012 study from the Argonne National Laboratory that found that, even including land use changes to grow corn, ethanol emissions are 19 to 48 percent lower than emissions from petroleum.

The new study looks only at the impact of biofuel production; it doesn't compare that impact to the environmental costs of the production, refinement and use of petroleum.

The study was conducted by researchers from the University of Wisconsin, Kansas State University and UC-Davis and was released by the National Wildlife Federation, a longtime opponent of the biofuel standards.

It should serve as a "wake-up call" to Congress and the EPA to push production away from corn and soybeans, said Collin O'Mara, the federation's president and CEO.

"We don't have to choose either/or," O'Mara said. "We can make sure agriculture families are still supported without having these negative impacts."