As rangeland productivity declines in developing countries, more forests and farmland are being converted to grazing. Overgrazing has degraded about 6. 8 million km of land. Followed Extraction Followed and charcoal are the primary sources of energy in many parts of the world. Each year an estimated 1 ,730 million mm of followed is taken from forests and plantations. As population pressure mounts, rural people are removing vegetation from higher and steeper areas, exposing more and more land to erosion. Followed extraction has degraded about 1. 37 million km of land. Agricultural Mismanagement
Soil nutrient loss occurs when land is farmed beyond its capacity. This is increasingly the case in areas of shifting (or “slash-and-burn”) cultivation, where population pressure has reduced fallow periods to virtually zero. Soil solicitation and waterlogged are caused by poor drainage of irrigated land. Agricultural mismanagement has degraded about 5. 5 million km of land. Arbitration Urban growth, road building mining and industry are degrading land worldwide. Often, valuable agricultural land is lost – during 1967-75, almost 30,000 km of good cropland disappeared under concrete in the United States alone.
Associated problems include pollution of soil by industrial and urban wastes, acid rain, overuse of inputs in feedlots, and oil and chemical spills. About 2. 4 million km has been degraded by chemical degradation. Water and Wind Erosion Water erosion affects mainly steep land or unprotected sloping areas. It causes soil losses estimated at 25,000 million tones every year. Wind erosion degrades land left bare of vegetation. It affects more than a third of land in the Near East and almost a quarter of Africa north of the equator.