To a geologist, erosion is the process that takes apart landforms. It wears or grinds them down, scouring away soil and rock with particles suspended in wind or water. It cracks off chunks of stone with the expansion of ice, and breaks down unprotected surfaces with the desiccating effects of heat.
Erosion is a natural force that has always shaped the world. However, agriculture, herding, and forestry can intensify and accelerate the forces of erosion, and can be factors in the destruction of fertile land.
Land use is probably the biggest factor affecting erosion. Where farmland is appropriately used, for example, erosion can be minimal or even nonexistent. Where land is overgrazed, over-plowed, or planted with inappropriate crops, topsoil is rapidly depleted.
Here are some of the factors that encourage erosion.
Overgrazing
Putting too many animals on a piece of land degrades it. Allowing animals to remain on the same piece of ground too long can also do great harm. Grazing animals can eat the land bare. The dominant plants of a piece of overgrazed land change, often in a way that makes it more susceptible to erosion.
Where vulnerable areas carry too many animals riverbanks are degraded, polluting streams and creating gullies and washes that increase the destructive effects of flowing water.
Tillage
Tillage, the preparation of cropland for planting by plowing or turning it, loosens and displaces soil. Topsoil from the higher parts of the land may come to rest in lower parts, and subsoil may be exposed. This eventually decreases farmers’ yields, and encourages water erosion, as the quality of the land is degraded.
No-till agriculture avoids tillage erosion, but is sometimes impractical. Farmers need new equipment. They may feel they need to use more herbicides, and yields are decreased, at least at first, on no-till farms.
Alternatives to no-till agriculture include strip-till and other conservation till methods. Each tries to prevent or slow soil erosion, while providing farmers at least some of the benefits of plowing.
Deforestation
Tree roots hold soil in place. When all the trees in a large area are removed, the earth will slide. Not only does this destroy forests, it pollutes the streams and rivers that drain them. Floods are another consequence, as the earth loses its ability to absorb water. Forest fires can cause landslides this way, and so can wildfires that strip chaparral or other growth on slopes.
Misuse
Some land is not suited to farming or grazing. Some hills are to steep to be logged. Some methods should not be used on certain terrain. In countries where impoverished people must misuse the land, the result is deforestation, land degradation, and a continuing cycle of poverty.
The Poverty-Environment initiative is a United Nations program that links improved living standards with concern for the environment. Read about it here.
