A new U-W Madison study says farm fields are releasing more of the carbon emissions that cause global warming in the years after corn based ethanol was required in gasoline. The study showed an increase of seven-million acres of cropland in the Midwest — mostly lands that used to be pastures, wetlands, and forests — and as a result, Wisconsin was ranked ninth in the additional releases of carbon from 2008 to 2012. That’s after a federal law from 2007 required most gasoline to have ethanol made from corn and sawgrass as ten-percent of its content to reduce the nation’s reliance on fossil fuels. The study showed changes in the rural landscape through satellite images and other data. But the Renewable Fuels Association, an ethanol trade group, questioned the validity of the maps and said other university studies “grossly overstated” land use trends in the wake of the ethanol mandate.