In simple terms
Erosion is the wearing away of the land surface, and the carrying of the loosened material somewhere else.
The UN Office for Disaster Risk Reduction defines it as the wearing away of the land surface by water, wind, ice, gravity or other natural or human agents that abrade, detach and remove soil particles from one point on the earth’s surface, for deposition elsewhere.
How it works
There are two steps. Something loosens the particles, and something carries them off. Rain striking bare soil does both at once. So does wind crossing a dry field.
UNDRR recognizes four forms: water, wind, harvest and tillage erosion. The UN Food and Agriculture Organization defines soil erosion more narrowly, as the accelerated removal of topsoil from the land surface through water, wind and tillage.
Erosion happens naturally, everywhere, under every climate. What changes is the rate. Both bodies name the same accelerators: intensive agriculture, deforestation, overgrazing and unsuitable changes in land use.
Rates are measured in megagrams per hectare per year, which is the same as tonnes per hectare per year. UNDRR treats 10 as the tolerable threshold. Its 2019 regional averages run from 2.6 in Europe and 2.7 in Oceania up to 12.8 in Asia, 17.1 in Africa and 22.0 in South America.
Why it matters
Soil does not come back on a human timescale. The FAO states it plainly: erosion rates are much higher than soil formation rates, so the loss is not recoverable within a human lifespan.
The scale is large. UNDRR puts annual global soil loss at about 75 billion tons and land loss at roughly 12 million hectares a year, and its climate projections point to water erosion rising by 30 to 66 percent across all scenarios.
What follows runs through everything built on soil: lower crop yields, higher flood and landslide risk, damaged infrastructure, lost biodiversity and, at the extreme, people having to move.
Where you’ll see it
- Farm conservation programs aimed at keeping topsoil in place
- Coastal and riverbank protection works
- Sediment controls around construction sites
- Land degradation targets in national climate and land plans
Example
Heavy rain falls on a bare, freshly plowed slope, and the runoff carries topsoil into the ditch at the bottom. The field loses a layer it will not get back in a lifetime.
Often confused with
Erosion is not weathering. Weathering breaks rock and soil down where they sit. Erosion includes moving the loosened material away and dropping it somewhere else.
Key facts
- UNDRR defines erosion as the wearing away of the land surface by water, wind, ice, gravity or other natural or human agents that abrade, detach and remove soil particles for deposition elsewhere.1
- FAO defines soil erosion as the accelerated removal of topsoil from the land surface through water, wind and tillage.2
- FAO states that soil erosion rates are much higher than soil formation rates, so the loss is not recoverable within a human lifespan.2
- UNDRR treats 10 megagrams per hectare per year as the tolerable threshold, against 2019 regional averages of 2.6 in Europe and 22.0 in South America.1
- About 75 billion tons of soil is lost globally each year, and roughly 12 million hectares of land annually.1
Related concepts
In the news
Quick checkWhat separates ordinary erosion from the kind that alarms scientists?Show answer
The rate. Erosion happens naturally everywhere, but farming, deforestation and overgrazing push it far past the rate at which soil forms.
Sources
- United Nations Office for Disaster Risk Reduction. Soil Erosion (GH0403). 7 June 2023 (accessed 17 September 2026)
- Food and Agriculture Organization of the United Nations, Global Soil Partnership. Soil erosion. Undated (accessed 17 September 2026)
Editorially reviewed by Specialty Digest Editorial TeamLast reviewed September 17, 2026Researched and drafted with AI assistanceReport an issue