Soils can be considered as a finite non-renewable resource. A resource is any material that is of benefit to human life. The formation of soils through weathering of the underlying parent rock, the formation of humus, and the development of a soil structure all require a long time. The time span for soil development depends on the intensity of the soil forming factors. On average, the formation of a soil layer a few centimetres thick in a humid climate takes several hundred years (Jenny, 1980; Tutzing Project, 1998). In relation to the time span of a human life, any loss of soil is to be considered permanent.

Soil degradation as defined for the Global Assessment of Soil Degradation (ISRIC, 1990) is ‘a process that describes human-induced phenomena which lower the current and/or future capacity of the soil to support human life’. In other words, soil degradation can be defined as human-induced deterioration of its quality, which means the partial or entire loss of one or more functions of soil (Blum, 1988). Soil quality then should be related to the potential socioeconomical and ecological soil functions. Important ecological soil functions include the ability to produce biomass, to store nutrients and water, to transform plant residues to soil humus (humification), and to release organically bound elements by mineralization (nutrient cycling). Furthermore, soils operate as a buffer against acidification and as a filter for pollutants protecting ground and surface waters. Soils are also the habitat for plant roots and countless soil organisms.