On August 29, 2016, the U.S. Geological Survey (USGS) published a study on the result of land-use changes on North and South Dakota commercial honey bee colonies in the journal Proceedings of the National Academy of Sciences. USGS scientists found that grasslands and other landscape features favored by beekeepers were decreasing, with crops that are avoided by beekeepers, such as corn and soybeans, replacing them. The study pointed out that biofuel crop production, including corn and soybeans, had increased in the Dakotas from 2006-2014, with a continual increase in biofuel crops totaling nearly three million acres around apiaries in the Dakotas. "According to the report, the Northern Great Plains have served as an unofficial refuge for commercial beekeepers because of their abundance of uncultivated pasture and rangelands, and cultivated agricultural crops such as alfalfa, sunflower and canola that provided forage for bees." The study identifies several areas in the Dakotas where honey bee habitat can be targeted for conservation, to increase forage availability and reduce the use of chemicals that negatively impact pollinators.