"It's been estimated that every year the United States loses about 4,000,000 acres of cropland (about the size of Connecticut) to erosion. This amounts to about 5 billion tons of topsoil in the U.S. alone. Worldwide, the annual loss is about 26 billion tons."
J. A. Schneider, “Environmental Investigations: Trouble in the Fields,” SUNY Oswego, 2003, http://www.oswego.edu/~schneidr/CHE300/envinv/EnvInv11.html.