In developing countries the land must feed farm families and their livestock, provide building material and fuel for cooking, and earn cash to buy whatever the farmers cannot grow themselves. With increasing population pressure in many areas, all these needs must be met from smaller and smaller land holdings. And as governments are forced to drop expensive subsidy programs, farmers must maintain the productivity of their fields with very little fertilizer, or none at all. Multipurpose trees are grown to provide more than one significant product or service to the farmer. They can contribute to rehabilitating degraded land and stabilizing soil, while providing animal fodder, fuelwood, food, and income for farm families.
Some multipurpose trees have another special value they fix nitrogen.
Nitrogen is a key nutrient for growing plants, and it is in short supply in many soils. More than 650 tree species are known to have the capacity to fix atmospheric nitrogen. These trees tend to be hardy pioneer species that grow well on poor or degraded sites, improving the soil for other plants. Publications FACT sheets on multipurpose trees. Aimed at extension agents, field researchers, community leaders, and farmers, these two-page summaries of current information are a handy reference for introducing promising multipurpose trees into research and planting programs.