Intensive grazing by animals, for example cattle, sheep or goats, on an area of pasture. It has become a serious threat to the world's rangelands and grasslands. Several factors have led to overgrazing, which leads to the soil being degraded and becoming liable to erosion by wind and rain, and even to desertification. The main pressures leading to widespread overgrazing have been the need to increase the size and numbers of herds to produce more food for an increasing human population, and the transformation of traditional pasture land into plantations to grow cash crops. Throughout the dry tropics, where traditionally herds ranged over vast areas, intensive livestock-rearing schemes have taken over, mostly to provide meat for the export market. Well-digging operations have also led to heavy concentrations of animals in small areas.