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soil erosion — English
The gradual wearing away of the top, fertile layer of the surface of the Earth. Erosion (see “erosion”) includes the weathering and removal of the rocks, rock debris, rock fragments and soil, but when we talk about soil erosion we are referring to the removal of that material which supports vegetated life on the surface of the Earth. Soil erosion is a natural process that has always occurred and will probably do so forever. However, over the last few thousand years human activities have resulted in accelerated soil erosion which is a much faster process that removes soil faster than it can be formed. This means that we are losing the productive capacity of the land on which we depend. The soil can be removed by sheet erosion which is the removal of a fairly uniform layer of soil by means of run-off water. Advanced sheet erosion progresses to rill erosion when numerous centimetres deep, small channels form in the surface layer. But as accelerated erosion continues surface run-off concentrates in the rills and enlarges them to gullies that are metres deep and hundreds of metres long. At that stage the land cannot be used for cultivation anymore and all the fertile topsoil has already been washed away. South Africa, Lesotho and Madagascar contain spectacular examples of erosion gullies, and that is unfortunately nothing to be proud of. Human activities that lead to this regrettable condition of millions of hectares of land all over the world are many and varied, but the main culprits are overcultivation, overgrazing, injudicious cultivation, slash-and-burn cultivation and general overuse of land. When too many people have to live off too small pieces of land or on land unsuitable for their traditional agricultural practices, the entire region might be degraded to a state of zero productivity. Millions of hectares in Africa have gone this route. Soil erosion is the most serious environmental problem humankind is facing, but it gets far less media coverage and publicity than air pollution, water pollution and global warming. It is good that people are aware of all the environmental issues, but our priorities are not always correct. Numerous international conferences and conventions have been held on air pollution, global warming and water pollution (see “climate change”, “environmental degradation”, “food security” and “environmental conventions”), but the most serious environmental problem, namely accelerated soil erosion has never formed the central focus of such a conference. Legally soils enjoy less protection than the atmosphere and the water networks, yet the most serious natural resource issue we are facing is the loss of our fertile topsoil!
