Soil erosion is the process by which wind, water, and other forces wear away the top layer of soil and move it somewhere else. It happens naturally over geologic time, but human activity has accelerated it dramatically. On agricultural land, soil now erodes 10 to 40 times faster than it forms, and an estimated 75 billion metric tons of soil are stripped from the earth’s surface every year, mostly from farmland.
How Erosion Works in Three Stages
All soil erosion follows the same basic sequence: detachment, transport, and deposition. First, something breaks soil particles loose from where they sit. Raindrops slamming into bare ground, wind gusting across a dry field, or even burrowing animals can do this. Once particles are free, they’re exposed to sideways movement.
During transport, those loose particles travel downhill in flowing water or blow across the landscape. Along the way, larger clumps of soil break apart further, releasing nutrients and organic matter that had been locked inside. Finally, the material settles somewhere new: a low spot in a field, a riverbank, a lake bottom, or an ocean floor. This final stage, deposition, is why eroded soil doesn’t just vanish. It ends up as sediment in places where it causes its own set of problems.
Water Erosion: From Raindrop to Gully
Water is the most widespread erosion force, and it works in escalating stages. The mildest form is sheet erosion, where raindrops hit the surface and dislodge tiny particles that wash away in a thin, almost invisible film of water. You might not notice it happening, but over a season it can strip a surprising amount of topsoil from an entire slope.
When that sheet of water starts to concentrate into small channels, you get rills. These are shallow grooves, typically less than four inches deep, running roughly parallel down a slope. Rills shift location from year to year and can usually be smoothed over by normal tillage. But when rills merge and dig deeper, they form gullies. Ephemeral gullies reappear in the same spots each growing season, even after a farmer fills them in, because the underlying drainage pattern doesn’t change. Over a few years the zone of soil damage around an ephemeral gully can widen to 100 feet or more. Left unchecked, gullies grow into permanent channels that no plow can fix.
How Wind Moves Soil
Wind erosion dominates in dry, flat landscapes with sparse vegetation. It moves soil particles in three distinct ways, sorted by size. The finest particles, smaller than about a tenth of a millimeter, get lifted into the air and carried long distances in suspension. These dust clouds can travel hundreds of miles.
Medium-sized sand grains (roughly 0.1 to 0.5 millimeters) are too heavy to stay airborne. Instead they bounce along the surface in short hops, a process called saltation. Each time a bouncing grain lands, it can knock other particles loose, creating a chain reaction that intensifies erosion. The coarsest sand grains (0.5 to 1 millimeter) never leave the ground but get nudged along by the impact of saltating particles. This surface creep accounts for roughly 7 to 25 percent of the total soil moved by wind.
Why Erosion Has Accelerated
Natural erosion is slow. Soil forms at a rate measured in fractions of a millimeter per year. Under undisturbed vegetation, erosion and formation roughly balance each other. Human activity broke that balance.
Conventional plowing is the biggest culprit. Erosion rates on plowed agricultural fields run one to two orders of magnitude faster than the rate at which new soil forms. That means for every inch of topsoil nature builds over centuries, farming can strip it away in years. Nearly one-third of the world’s arable land has been lost to erosion over a roughly 40-year period. Deforestation, overgrazing, mining, and logging all contribute as well, each one removing the vegetative cover that holds soil in place. Research comparing countries that share a border, and therefore share the same natural erosion conditions, found significant differences in erosion rates driven entirely by differences in agricultural practice.
What Erosion Does to Crop Yields
Topsoil is where most of the organic matter, nutrients, and microbial life that plants depend on are concentrated. Losing it has a direct, measurable effect on what farmers can grow. Research from Washington State University tracked yields as topsoil depth dropped from 15 inches to 5 inches and found that wheat and sweet corn yields declined at about 3.5 percent per inch of topsoil lost. Barley, dry beans, and alfalfa showed similar but slightly less severe declines. Even sugarbeets, the most tolerant crop studied, still produced less as topsoil thinned.
That yield loss compounds over time. A field that has already lost several inches of topsoil doesn’t just produce less food today. It also has less capacity to absorb and hold water, making it more vulnerable to drought and to further erosion in the next heavy rain.
Damage to Water and Ecosystems
The soil that leaves a field doesn’t disappear. It enters streams, rivers, and lakes as sediment, and it carries nutrients with it. Phosphorus, which binds tightly to soil particles, is primarily lost through erosion rather than through water seeping underground. Agricultural soils worldwide lose an estimated 4 to 19 kilograms of phosphorus per hectare per year to erosion, amounting to over half of total phosphorus losses in the agricultural system. In some watersheds, erosion-based phosphorus input rivals or exceeds what enters waterways from sewage.
That phosphorus, along with nitrogen carried in runoff, feeds explosive algae growth in lakes and reservoirs. This process, called eutrophication, depletes oxygen in the water, kills fish, and contaminates drinking water supplies. A study of European lakes confirmed that soil erosion is a key driver of eutrophication across nearly every region examined. Steeper slopes and higher elevations make the problem worse because phosphorus-rich topsoil washes off faster.
Climate Change Is Making It Worse
Warmer temperatures are intensifying the water cycle, producing heavier and more erratic rainfall events. Climate projections estimate that global water erosion could increase by 30 to 66 percent by 2070 depending on the scenario. The relationship is straightforward: more intense rain hits the ground harder, dislodges more soil, and generates more runoff. Regions already prone to erosion will see the fastest increases, while areas experiencing more frequent drought will face greater wind erosion as vegetation thins and soil dries out.
The Economic Cost
The United Nations estimates that desertification, land degradation, and drought together cost the global economy $878 billion every year. Soil erosion is at the center of that figure. The costs include lost agricultural productivity, increased spending on water treatment to remove sediment and nutrients, dredging of silted-up reservoirs and waterways, and damage from flooding made worse when degraded soils can no longer absorb heavy rain.
Practical Ways to Reduce Erosion
The most effective erosion control strategies work by keeping soil covered and its structure intact. No-till farming, where farmers plant directly into undisturbed soil without plowing, is one of the most impactful changes. The crop residue left on the surface shields the ground from raindrop impact, slows water flow, and reduces wind exposure. For farmers who can’t fully eliminate tillage, seasonal no-till (tilling once every two years or less) still cuts erosion and nutrient runoff significantly.
Several variations exist for different situations. Ridge tillage builds raised beds that slow water and direct it away from crops. Strip tillage plows only narrow bands where seeds will go, leaving the soil between rows undisturbed. Mulch tillage uses conventional plowing but scatters plant material over the surface afterward to protect it.
Cover crops, planted between growing seasons specifically to hold soil in place, are another powerful tool. Their root systems bind soil particles together while their leaves intercept rain before it hits bare ground. Combined with contour plowing, where rows follow the natural curve of a slope rather than running straight downhill, and terracing on steeper land, these practices can bring erosion rates much closer to the natural baseline. The core principle is simple: bare soil erodes, covered soil doesn’t.