SIOUX FALLS, S.D. (AP) — A new study documents a loss of 1.3 million acres of grassland over a five-year period in the Western Corn Belt — a rate not seen since the 1920s and 1930s.

The research by Christopher Wright and Michael Wimberly of the Geographic Information Science Center of Excellence at South Dakota State University said a recent doubling in commodity prices has created incentives for landowners in South Dakota, North Dakota, Nebraska, Minnesota and Iowa to convert grassland to corn and soybean cropping.