| definition |
- The wearing away of the land surface by rain or irrigation water, wind, ice, or other natural or anthropogenic agents that abrade, detach and remove geologic parent material or soil from one point on the earth's surface and deposit it elsewhere, including such processes as gravitational creep and so-called tillage erosion; The detachment and movement of soil or rock by water, wind, ice, or gravity.
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| Abstract from DBPedia | Soil erosion is the denudation of the upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, and animals (including humans). In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, wind (aeolean) erosion, zoogenic erosion and anthropogenic erosion such as tillage erosion. Soil erosion may be a slow process that continues relatively unnoticed, or it may occur at an alarming rate causing a serious loss of topsoil. The loss of soil from farmland may be reflected in reduced crop production potential, lower surface water quality and damaged drainage networks. Soil erosion could also cause sinkholes. Human activities have increased by 10–50 times the rate at which erosion is occurring world-wide.Excessive (or accelerated) erosion causes both "on-site" and "off-site" problems. On-site impacts include decreases in agricultural productivity and (on natural landscapes) ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the eventual end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of water bodies, as well as sediment-related damage to roads and houses. Water and wind erosion are the two primary causes of land degradation; combined, they are responsible for about 84% of the global extent of degraded land, making excessive erosion one of the most significant environmental problems worldwide. Intensive agriculture, deforestation, roads, acid rains, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion. However, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils.土壌流出（どじょうりゅうしゅつ）とは、地面の傾斜や風などの影響によって表面の土壌が流亡する現象のことである。アメリカ合衆国の畑作でしばしば問題視され、1トンの小麦を生産する際に約1トンの肥沃な土壌が流失していると言われている。 土壌流出の量は農法や地形等によって変化する。また、土壌流失は森林の伐採や過度の放牧などにより、地表を覆っていた植物層が失われ、地表が露出した場合に、雨や風の影響を受けて発生する。このことは浸食作用を受けやすい山地において著しく、保水力の低下や下流域での洪水の要因になるとともに、世界の5分の1から3分の1に及ぶ地域での農地の生産性低下の原因になっているとみられている。これらを防ぐために等高線状に耕地を造成する等高線耕作や防風林造成などによって対策がとられることもあるが、しばしば放棄され大規模に砂漠化（土漠化）することも多い。 (Source: http://dbpedia.org/resource/Soil_erosion) |
