A few years ago, Isaac Larsen attended a wedding at a pioneer church in Minnesota. After the ceremony, he wandered around a cemetery by the church. He noticed the cemetery, which had never been tilled, was at least a foot higher than a corn field just on the other side of a fence. “That was one of those ‘lightbulb’ moments that told me that a lot of soil had been eroded from that field since the founding of the church,” Larsen said. The University of Massachusetts Amherst geosciences professor and his co-researchers have released a new study that found topsoil in the Midwest is eroding at an average rate of 1.9 millimeters per year. They measured elevation differences between native prairie and farm fields at about 20 sites, the majority in central Iowa, with some in Illinois, Minnesota, South Dakota, Kansas and Nebraska.