Soil Erosion Threat Increasing with Climate Change

Soil erosion remains a top priority for sustainable crop production in the United States, with average soil erosion rates by wind and water still at 4.63 tons per acre per year (T/A/yr), and total soil loss of 1.70 billion tons on a national level (data from USDA-NRCS 2017 National Resources Inventory Summary Report [PDF]). Expressed in dollars at a minimum price of $7.50 per ton of topsoil, this represents a whopping $12.75 billion annual economic loss to farmers, which equals about a quarter of the total U.S. soybean crop value (25% of 4 billion tons @ $12/bu).

These numbers don’t include tillage erosion, which causes topsoil translocation from high to low spots in a field. A recent remote sensing study [The extent of soil loss across the US Corn Belt, Thaler, Larsen, Yu (2020)] concluded that one-third of the Corn Belt has lost the entire A horizon (the organic matter-enriched topsoil layer), due to tillage erosion, causing an average 6% crop yield reduction and an estimated annual economic loss of $2.8 billion (Thaler et al., 2021).

The challenges of soil erosion are not likely to become less. The Fifth National Climate Assessment, published by the U.S. Global Change Research Program in 2023, documents the changes in the climate in the Northeast, defined as the area from Maine in the north to Maryland in the south and West Virginia and Pennsylvania in the west. The assessment shows a trend of increasing precipitation in the Northeast. Most importantly, intensive precipitation events are increasing. For example, the number of events with >3 inches/day of precipitation showed an average 62% increase between 1958 and 2018, while events >5 inches/day increased 103%. Further, the climate is warming, especially in the winter. This means fewer days that the soil is frozen, and more precipitation that falls as rain instead of snow.

These trends are expected to continue in the future, with important implications for soil erosion and conservation. As discussed in a previous article, Soil Erosion Continues to be a Concern in Pennsylvania (Duiker, 2021), average soil erosion from Pennsylvania cropland is still estimated to be more than 4 T/A/yr, a rate that is not sustainable.

What is worse, we tend to present erosion rates as annual averages, but in reality, most erosion occurs during high-intensity rainstorms. This was illustrated in a study in corn-soybean rotation without cover crop (Journal of Soil and Water Conservation) in Greensboro, North Carolina, where more than half of the erosion in a 6-year period occurred during one week of highly erosive precipitation events (Raczkowski et al., 2009). In this study on a (sandy) clay loam with modest 4–6% slopes, average soil loss was 33.3 T/A/yr with spring chisel/disking, and 1.2 T/A/yr with no-till. However, 135 T/A was lost from the chisel/disk treatment in one week in July 1997. 

This study is another reminder of the importance of keeping our soils covered permanently. Some have suggested that rotational tillage is no big deal because, on average, the soil is covered most of the time. However, if the soil happens to be loosened by tillage and without cover at a time when high-intensity rainstorms hit the area, our efforts might all be in vain with apocalyptic soil loss in very short periods of time. For that reason, continuous no-tillage systems with permanent organic cover are essential to preserve our soils.