Posted 14 April 2021:
Scientists and farmers know that agricultural soil erosion has been a problem for decades, but quantifying soil loss from a hundred years of farming and across multiple states has proven difficult. Now a study led by geomorphologist Evan Thaler and published in Proceedings of the National Academy of Sciences in February attempts to answer the elusive question of how much topsoil has been eroded in the Corn Belt, which stretches roughly from Ohio to Nebraska and produces 75 percent of the nation’s corn. The study estimated that about 35 percent of the region has lost its topsoil completely, leaving carbon-poor lower soil layers to do the work of supporting crops. Having thick, healthy topsoil means plants can grow faster and healthier, increasing crop yields and keeping the field’s ecosystem running smoothly. Topsoil loss creates environmental problems, such as when eroded, nutrient-laden dirt degrades streams and rivers, and is estimated to cost the Midwest’s agricultural industry almost $3 billion annually.
“I think it’s probably an underestimate,” says Thaler, a graduate student at the University of Massachusetts–Amherst. “There are areas where there’s probably a centimeter of topsoil left.”