Biofuel Demand Takes Big Toll on US Prairies Grasslands destroyed at fastest rate since 1930s, says study By Matt Cantor, Newser User Posted Feb 20, 2013 2:10 PM CST 45 comments Comments A handful of corn is shown before it is processed at the Tall Corn Ethanol plant, May 24, 2006, in a Coon Rapids, Iowa file photo. (AP Photo/Charlie Neibergall, File) (Newser) – The push for biofuels—spurred by ethanol mandates and government subsidies—is taking a serious toll on the American landscape, a study finds. Grasslands are being plowed up faster than at any time since the 1930s, say researchers from South Dakota State University, with 1.3 million acres turned into corn and soybean territory between 2006 and 2011. Iowa and South Dakota, for instance, are seeing 5% of their pastures converted to cropland annually, the Washington Post reports. The speed of the process is "comparable to deforestation rates in Brazil, Malaysia, and Indonesia," say the study's authors. That's causing multiple problems: For one thing, it's a climate-change threat, because grasslands are thought to retain carbon better than croplands. It's also a threat to farmers themselves, who are being pushed toward land with a high drought risk. And it poses a danger to bird populations that breed in the area.