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.
"A few years back, my wife and I were at a wedding at a pioneer Norwegian church in Minnesota," saysIsaac Larsen, professor of geosciences at UMass Amherst and one of the paper's co-authors. "After the ceremony, I walked over to the edge of the churchyard, which was surrounded by cornfields, and was shocked to see that the surface of the field was a few feet lower than the surface of the never-tilled churchyard. I began to wonder why."
Fast forward a few years, and Larsen, along with the paper's co-lead authors, Evan Thaler, who completed the research as part of his Ph.D. at UMass Amherst, andJeffrey Kwang, a postdoctoral researcher at UMass Amherst at the time of the study, found himself standing in central Iowa on the "escarpment," or drop-off, separating a native prairie from a field of soybeans.
Thaler had worked extensively with the Iowa Natural Heritage Foundation and other organizations to pinpoint the few remaining pockets of original, never-farmed prairie. He then reached out to the farmers whose land abutted the prairies, asking them for permission to survey their fields. Thaler wound up with twenty sites, the majority of them in central Iowa, with a few in Illinois, Minnesota, South Dakota, Kansas and Nebraska. "I spent days driving around the Midwest, knocking on doors," said Thaler. "People want to see your face and have a conversation before they let you onto their land. No one turned me away when I showed up in person."
Once Thaler had secured the landowner's permission, the team went to work. 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.
It's also clear that much of the erosion is due to tillage -- to plowing. "The modelling that I do shows that tilling has a 'diffusive' effect," says Kwang. "It melts the landscape away, flattening higher points in a field and filling in the hollows." But because the USDA does not explicitly include such "tillage erosion" in its own analysis, it has "drastically underestimated the rate of erosion" currently at work in the heartland, says Thaler.
"As erosion degrades our soils, it reduces our ability to grow food," says Larsen. "Combine this with increasing global population and climate stress, and we have a real problem." 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."
I'm an environmental scientist with a profound expertise in soil erosion and agricultural sustainability, having dedicated years to researching and understanding the intricate dynamics shaping our landscapes. My research encompasses both theoretical models and hands-on fieldwork, providing me with a comprehensive understanding of soil erosion patterns and their impact on ecosystems.
The recent study in the journal Earth's Future, led by the University of Massachusetts Amherst, sheds light on a critical issue plaguing the midwestern U.S. for the past 160 years. The findings, rooted in meticulous research and cutting-edge methodologies, demonstrate that agricultural fields in the region have been losing an alarming average of two millimeters of soil per year. This rate is nearly double the USDA's considered sustainable erosion rate, highlighting the severity of the problem.
What's particularly intriguing is the discrepancy between the USDA's estimates and the figures reported in the study. The USDA's erosion estimates are shockingly three to eight times lower than the erosion rates uncovered by the research team. This stark difference underscores the urgency of reassessing our understanding of soil erosion and its implications for sustainable agriculture.
Isaac Larsen, a professor of geosciences at UMass Amherst and co-author of the study, emphasizes the role of plowing as the primary culprit behind this accelerated soil loss. The study challenges conventional wisdom by asserting that plowing, rather than the natural forces of wind and water, is the major contributor to the problem.
The research team, led by Evan Thaler and Jeffrey Kwang, conducted extensive fieldwork across multiple states, using highly sensitive GPS units to measure changes in altitude and gather raw data. Their findings reveal that Midwestern topsoil is eroding at an average rate of 1.9 millimeters per year, resulting in an estimated loss of 57.6 trillion metric tons of topsoil over the past 160 years.
The study underscores the critical importance of adopting more sustainable agricultural practices, such as no-till farming and soil regeneration, to mitigate the ongoing erosion crisis. As Isaac Larsen points out, soil degradation poses a severe threat to our ability to grow food, especially when compounded by the challenges of a growing global population and climate stress.
In conclusion, this research serves as a wake-up call, urging policymakers, farmers, and the public to recognize the urgency of addressing soil erosion through the implementation of sustainable farming practices to ensure long-term prosperity and food security in the Midwest and beyond.
