Midwestern US Has Lost 57.6 Trillion Metric Tons of Soil Due To Agricultural Practices, Study Finds
An anonymous reader quotes a report from Phys.Org: A new study in the journal Earth's Future led by the University of Massachusetts Amherst shows that, since Euro-American settlement approximately 160 years ago, agricultural fields in the midwestern U.S. have lost, on average, two millimeters of soil per year. This is nearly double the rate of erosion that the USDA considers sustainable. Furthermore, USDA estimates of erosion are between three and eight times lower than the figures reported in the study. Finally, the study's authors conclude that plowing, rather than the work of wind and water, is the major culprit. Using an extraordinarily sensitive GPS unit that looks more like a floor lamp than a hand-held device, the team walked dozens of transects, or perpendicular routes across the escarpment, from the untouched prairie to the eroded farm field, stopping every few inches to measure the change in altitude. They did this hundreds of times throughout the summers of 2017, 2018 and 2019. Once they had their raw data, the team used historical land-use records and cutting-edge computer models to reconstruct erosion rates throughout the Midwest. What they discovered is that Midwestern topsoil is eroding at an average rate of 1.9 millimeters per year. Put another way, the authors estimate that the Midwest has lost approximately 57.6 trillion metric tons of topsoil since farmers began tilling the soil, 160 years ago. And this is despite conservation practices put in place in the wake of the Dust Bowl in the 1930s. As noted above, much of the erosion was due to tillage, or plowing. "The modeling that I do shows that tilling has a 'diffusive' effect," says Jeffrey Kwang, a postdoctoral researcher at UMass Amhers. "It melts the landscape away, flattening higher points in a field and filling in the hollows." Furthermore, the USDA doesn't include "tillage erosion" in its own analysis, meaning it's drastically underestimated the rate of erosion that's occurred in the area. The team suggests that more sustainable practice, such as no-till farming and soil regeneration, "will likely be required to reduce soil erosion rates in the Midwest to levels that can sustain soil productivity, ecosystem services, and long-term prosperity."
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