These farmers' ability to feed themselves and to earn additional monies to improve their lot is critical to the survival of entire societies. The challenge is enormous. First, the number of mouths to feed is growing steadily. Global population by 2025 is expected to be twice that of 1980. Second, farmers must grow their crops on roughly the same amount of land since most of the world's arable land is already under the plough or pasture.
Grasslands become deserts when vegetation growth is reduced to a minimum.
In Africa, where the numbers of both people and animals have exploded, overgrazing in some countries is thought to exceed the carrying capacity of the range by 100 per cent. As more and more land is brought into permanent cultivation, the pastoral herding people are forced into marginal lands. In Central America, the problem of too many people on too little land is compounded by perverse patterns of land use and distribution. Meanwhile, the small, land-poor farmers are driven either to cultivate hillsides or to cut down more forests. But the uncovered hillsides are more susceptible to erosion and soils wash away in a few years, while tropical forest soil is rarely suitable for intensive or prolonged cultivation.