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FAO's 2026 soil assessment ranks erosion among the most serious threats to the world's soils
FAO's Status of the World's Soil Resources 2026 ranks erosion among the most serious threats to soils, saying soil can be lost far faster than it regenerates. The best-measured case behind that warning is the US Corn Belt, where eroded farmland is already costing yield and money.
The Scientist · Science desk
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What happened
- Isaac Larsen, an associate professor in UMass's Department of Earth, Geographic, and Climate Sciences, is one of the report's lead authors.
- Larsen's research feeds the report's comparison of human-caused erosion with the natural rate at which soil forms.
- A 2021 study he co-authored, cited in the report, estimated that about 35% of cultivated Corn Belt land had lost A-horizon soil, cutting regional crop yields by 6%.
- The report points to reduced tillage, cover crops, crop diversification and agroforestry as ways to reduce erosion.
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Why it matters
- cost Conservation spending in the Corn Belt now has a measured loss to be judged against: USD 2.8 billion a year from lower crop yields.
- constraint Larsen's North America chapter calls for improved assessment methods, so any scheme that pays for avoided erosion depends on measurement that is still being developed.
- decision The report is aimed at policy, so the next choice falls to governments deciding whether to reward farmers for practices that conserve soil.
Larsen described the job as synthesis. "Our charge was to synthesize a decade's worth of research on the current condition and threats to soils, and to do so in a way that makes that information accessible to policymakers," he said [5]. The assessment is assembled from recent scientific literature and from contributions by hundreds of experts [2].
The Corn Belt estimate is the one place in the coverage where soil loss has been both mapped and priced. It came from satellite imagery combined with field data [7]. Its denominator is narrow: cultivated land in a single US study region [7].
The yield figure says something about where the damage sits. Suppose the entire 6% regional shortfall came from the eroded 35% of fields, and those fields would otherwise yield about as much per hectare as the rest. Then eroded ground is producing roughly 17% less than it could [14]. The study did not report that number, and it holds only under those two assumptions.
Larsen's methods are designed to measure loss after it has happened. In his studies he has combined precise surveying, satellite images and geochemistry to quantify erosion and work out how much soil was lost in the past [9]. I think that evidence supports treating Corn Belt farm soil as a stock being drawn down, since on much of its cultivated area the A-horizon soil is already gone [7]. The global version of the claim rests on the report's synthesis. The phys.org account does not include the worldwide erosion and formation rates the report compares.
Larsen sees the remaining problem as one of practice. "The report demonstrates that there has been substantial growth in the science underpinning sustainable soil management practices, but at the same time, it concludes that most of the world's soils are being managed in ways that are unsustainable," he said [11].
He wants the report to change incentives. "I hope the report draws attention to the disparity between what we know and what we do, and enables policymakers to better incentivize farming practices that conserve and regenerate soil," he said [12].
What to watch
- Publication of the global erosion and soil formation rates behind the report's conclusion, broken out by region.
- Field measurements of how much reduced tillage, cover crops, crop diversification and agroforestry each cut erosion on working farms.
- Results from Larsen's ongoing erosion projects supported by the UMass Center for Agriculture, Food, and the Environment.