With thanks to Gillian Dorfman for this information compiled from Outreach packs 101, 102, 103. Produced by Outreach, 200 East Building 239 Greene St, New York University, NY 10003, USA and Outreach Regional Office, UNEP, PO Box 30552, Nairobi, Kenya.
Just as the world’s population and poverty are increasing, so also is the destruction of our precious natural resources. There are many factors which link together and result in land becoming less productive.
Soil takes thousands of years to form but it can be destroyed extremely fast by careless or inappropriate activities of people.
Bad land use practices cause the loss of topsoil which triggers a chain reaction of events, not just in the region immediately affected by the soil erosion.
Soil layers
Soil has several layers. However, it is the thin top layer, the topsoil, which is the fertile part where crop and tree roots obtain nutrients. Erosion removes the topsoil, leaving the hard, infertile subsoil, which is of little use for growing crops.
You can see these layers when foundations are dug for a building or when a new road is built going through a hillside
Soil erosion
This happens when soil cover is removed, exposing the soil to the effects of wind and rain.
During heavy rain soil is washed away into rivers, lakes and seas. Not only is it lost to the farmer, but it also silts up water sources and coast lines, affecting fish production.
Overgrazing
This happens when too many animals graze on the same area of land. Unless controlled, grazing animals will eat grass and other plants down to the roots, leaving the soil exposed to erosion. Plants which are good for animals to eat and are effective at holding the soil together, may disappear and be replaced by plants which are of little use either for grazing or to protect the soil.
Deforestation
Trees protect the soil from erosion. When they are cut down, the productive soils in which they grew can be quickly washed away.
Logging
All around the world logging companies, landowners and governments are clearing forests to earn money from the timber. Sometimes the land is replanted with trees, but often this is not done. The world’s forests are disappearing 30 times faster than they are being re-planted.
Flooding
If forests and vegetation cover are removed, when heavy rains come the rain no longer soaks into the soil but runs off down hillsides. Rivers overflow and flood towns and cities downstream.