A global ban on genetically modified crops would raise food prices and add the equivalent of nearly a billion tons of carbon dioxide to the atmosphere, a study by researchers from Purdue University shows. Using a model to assess the economic and environmental value of GMO crops, agricultural economists found that replacing GMO corn, soybeans and cotton with conventionally bred varieties worldwide would cause a 0.27 to 2.2 percent increase in food costs, depending on the region, with poorer countries hit hardest. According to the study, published Oct. 27 in the Journal ofEnvironmental Protection, a ban on GMOs would also trigger negative environmental consequences: The conversion of pastures and forests to cropland - to compensate for conventional crops' lower productivity - would release substantial amounts of stored carbon to the atmosphere.