Impact of Land Use on Soil Resources.

The land system is a coupled human-environment system comprising land use, land cover, and terrestrial ecosystems (Global Land Project, 2005). Land use connects humans to the biophysical environment. Conversely, the characteristics and changes in the biophysical environment influence our land-use decision-making. Thus, there is a continuum of states resulting from the interactions between natural (biophysical) and human (social) subsystems of land (Fig. 1.1). Though not always, the dynamics of this continuum generally moves toward increasing human dominance and impact. Thus, mitigating adverse environmental changes requires an improved knowledge of human impact on natural processes of the terrestrial biosphere. Soil is a basic resource for land use. It is the foundation of all civilizations (Hillel, 1992), serves as a major link between climate and biogeochemical systems (Yaalon, 2000), supports biodiversity, and plays an important role in the ability of ecosystems to provide diverse services necessary for human well-being (Young & Crawford, 2004). Thus, soils must not be neglected in any development endeavor either at local, regional, or global level. Good soils are not evenly distributed around the world. Depending on parent material, climate, relief, vegetation, and time that determine soil formation, soils have inherent constraints that limit their productivity for various uses. Most soil constraints are not mutually exclusive. For instance, highly acidic soils with aluminum toxicity also have high phosphorus-fixation capacity. The inherent constraints of soils for agricultural production vary widely across regions. For example, erosion hazard, defined as very steep slopes (>30%) or moderately high slope (8-30%) accompanied by a sharp textural contrast within the soil profile, varies from 10% for soils of North Africa and Near East to 20% for soils of Europe. On the other hand, shallowness, the occurrence of rocks close to the soil surface, varies from 11 percent for soils of South and Central America to 23% for soils of North Africa and Near East (FAO, 2000). [ABSTRACT FROM AUTHOR]