Soil Resources and Soil Degradation

Abstract

The total land area of the world is estimated to be 130,575,894 km2, including rocky surfaces, deserts, ice-covered areas, and lands with soil. Only about 12 % land is suitable for agricultural crop production without much limitation, 24 % is used for grazing, and 31 % is occupied by forests. The remaining 33 % has too many constraints for most uses. Not all agricultural soils are fertile and productive. Some soils are naturally unproductive; some are arid and saline; some are very sandy and dry; some are wet and waterlogged for most of the growing season. Some soils have been degraded by human activity. Recent estimates suggest that land degradation affects 3,500 M ha or 23.5 % of the Earth’s land area and impacts 1.5 billion people. GLASOD recognizes five types of soil degradation processes—water erosion, wind erosion, chemical deterioration, physical deterioration, and degradation of biological activity. Soil erosion along with compaction and surface sealing is considered to be a physical degradation process. There are on-site and off-site effects of water and wind erosion. These processes may also lead to desertification in arid and semiarid regions. Many soils have been salinized by soil mismanagement, including modification of hydrology through irrigation and drainage. Some soils have been polluted by organic and inorganic pollutants. Degraded soils need sustainable management.