<P> Soil erosion is the displacement of the upper layer of soil, one form of soil degradation . A low level of erosion of soil is a naturally occurring process on all land . The agents of soil erosion are water and wind, each contributing a significant amount of soil loss each year . 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 . </P> <P> Human activities have increased by 10--40 times the rate at which erosion is occurring globally . 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 . </P>

What is soil erosion and what are the main causes of soil erosion
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