Improving yields on marginal land. FAO estimates that there may be some two billion hectares of marginal land that could be converted to agriculture, but three-quarters of it is too dry, too steep, too wet, too cold, or too shallow to support sustainable food production (98, 99). There is some scope for introducing more efficient farming techniques to help subsistence farmers working marginal lands, however.

For example, the International Institute of Tropical Agriculture has pioneered "alley farming," which could substitute for slash-and-burn, shifting cultivation on fragile and highly erodible tropical soils. Alley farming is now being introduced in over 20 countries in Africa and Asia (48). The concept is simple: leguminous crops, such as mucuna, which fix nitrogen and improve soil organic matter, are planted between rows of food crops, such as peas and beans. The legumes help hold the soil in place and improve nutrient content while preventing weeds from taking root. If crops are used in the right combination, alley farming can greatly improve yields on poor soils in hilly regions and thus reduce the need to clear forests for farmland.

Farming forests. Forests are generally worth more standing and managed sustainably than when cut down for short-term profit. For example, in Peru harvesting forest products from one hectare could be worth over US$400 annually, year after year. Logging the same area and selling the timber would yield a one-time return of $1,000 (98). FAO studies in Peru, the Brazilian Amazon, the Philippines, and Indonesia suggest that harvesting forest products on a sustainable basis is twice as productive in the long-run as clearing forests for agricultural and grazing land (99). Cleared land often takes 50 to 100 years to recover. Furthermore, once forest is cleared, the biological diversity of secondary growth never matches that of pristine wilderness (35).

Many plant products found in forests are harvested for food. These include mushrooms, coconuts, saps, and gums. The sago palm is a food staple for more than 300,000 Melanesians. Grasses, foliage, and bamboo are used as animal fodder and for building materials. Forests contain thousands of different species of plants that could be used for medicines and pharmaceuticals. For example, a derivative of the rosy periwinkle, found in Madagascar, has improved the survival of children suffering from leukemia. Taxol, found in the western yew, which grows in the forests of the American northwest, is being used in anti-cancer drugs (54).

Forest plants and trees are also exploited for horticulture and extractive products such as natural rubber, oils, and resins. Some 1.5 million people in the Brazilian Amazon derive a major portion of their income from harvesting natural rubber and other forest products (98). Vines and fibers are used in furniture making. Rattan supports a thriving furniture industry in Southeast Asia, bringing in US$2 billion a year (98, 99).

Expanding aquaculture. About 17% of the world's animal protein for human consumption comes from fish. In some Asian countries that figure is over 50%. Between 1984 and 1994 the amount of fish and other products farmed in the sea and from freshwater ponds more than doubled, rising from 10 million metric tons to 23 million metric tons (98, 99).

In the developing world, where the world's aquaculture and mariculture industries are concentrated, most fish farming operations are for export and not for local consumption. Exports of such species as shrimp, prawns, and grouper bring in substantial foreign exchange earnings for a number of poor countries. Where farming fish for local consumption has been tried, the results have been encouraging.

For example, faced with the loss of their livelihoods because of overfishing and increased competition from commercial trawlers, poor fishing communities in Capiz Province, on the island of Panay, the Philippines, turned to fish farming and crab fattening. The mariculture operations were established by the women of these fishing villages with loans and technical assistance from the Philippine offices of FAO and the United Nations Population Fund. As part of the project, the women were offered family planning, and in a few years over half were using contraception. With smaller families, the women's health is better, they are able to earn more money, and their children are able to stay in school longer (40).

Fish farming, shown here in Nepal, is expanding in many countries but remains short of compensating for declines in ocean catches worldwide, including areas such as the Philippines (inset).

Rediscovering forgotten foods. Another way to help make up for food shortages, especially in the world's poorest countries, is to rediscover forgotten traditional food plants. Amaranth and quinoa, two grains that historically were cultivated by the Incas of Peru and the Aztecs of Mexico, provide examples. Both grains are versatile and nutritious foods, containing more high-quality protein than most other commercial grains, including corn, rice, and wheat (127). Moreover, both grow well under difficult conditions. Amaranth thrives in hot climates. The quinoa plant, because it is frost-resistant, can be grown at high altitudes (39).

Encouraging urban agriculture. As cities continue to expand in developing countries, people are growing more and more food in urban areas (37). Worldwide, some 200 million city dwellers are growing food, providing about 1 billion people with at least part of their food supply (63, 93).

The scale of urban agriculture varies a great deal, including household gardens covering no more than 20 square meters, small commercial operations occupying 200 to 1,000 square meters, and greenhouses that cover 20 to 30 hectares. Some urban farmers raise fish, shellfish, and aquatic plants in small tanks, ponds, sewage lagoons, and estuaries. Others use vacant city lots to grow vegetables and fruits. Still others keep guinea pigs, rabbits, and chickens in cages hung on walls or grow vegetables using hydroponic techniques (63, 93).

Urban farmers produce impressive amounts of food. In Accra, Ghana, for example, urban gardens supply the city with 90% of its vegetables. In Dar-es-Salaam, Tanzania, one adult in every five grows fruits or vegetables. Over 60% of the area around Bangkok has been devoted to vegetable gardens, cultivated mostly by women and children (63, 93).

Adopting new approaches. Some countries with traditional farming systems are improving yields with new approaches that use low-level agricultural inputs—fertilizing with animal wastes instead of chemicals, recycling nutrients, conserving water, and selecting a variety of crops well-suited to soil conditions and climate (98, 99, 110, 111, 112). In Indonesia, for example, the Javan rice crop was nearly wiped out in 1984 by a plague of pesticide-resistant brown plant hoppers. In response, the government introduced a new approach, Integrated Pest Management (IPM) (127).

IPM involves taking several related steps—preserving natural pest predators, using pest-resistant seed varieties, and drastically reducing the amount of chemical pesticides used. Using this approach, the infestation of brown plant hoppers was controlled with only minimal crop losses (98). Within a few years, Javanese farmers who used the IPM methods had higher yields than those who continued to spray their crops with pesticides (98).