When you imagine the Midwest, what do you picture? I think of endless farmland under bright blue skies, with crops stretching out to the horizon. Silos and fences dot the scenery.
Such a bucolic setting gave researchers the topic of a study. Sure, farms spread across the Midwest now, but 200 years ago, it was native prairies that dominated, with their wild tallgrasses waving in the breeze. Fragments of these prairies still exist in small patches, and at the meeting of prairie and agricultural field you can find something called an “erosional escarpment.” Prairieland sits about a foot higher than farmland, and the escarpment is the short, steep slope of ground between prairie and farm. Over nearly two centuries, cultivated fields have lost topsoil, creating the elevation difference between the two terrains.
Escarpments are a stark reminder of why Midwest farmland sits below the original prairie. According to the study, erosion has caused over 57 billion tons of topsoil to be lost from Midwest farms, with more eroding every year. Much of this can be attributed to tillage: plowing, digging, and preparing the ground for crops disturbs the topsoil. Shaken loose, the soil gets carried away by wind and water. The researchers argue that the long-term erosion rate, about 1.9 millimeters per year, is unsustainable: those pastoral fields of corn and soybeans need topsoil’s nutrients to survive.
Some scientists dispute the findings, saying that the yearly rate of erosion is far less than the study indicates. Nevertheless, topsoil’s disappearance could spell trouble for Midwestern farmers.