Rapid population growth in Africa, without corresponding improvements in agricultural technology, has intensified pressure on arable land, leading to its overuse and the extension of cultivation onto unsuitable or marginal lands. It also has generated greater demand for fuelwood, building materials, and other products traditionally extracted from the forest. The result has been growing deforestation, increased wind and water erosion, and declining productivity of agricultural lands.
Faced with this spiral of environmental degradation, African governments and external donors have sought ways to reverse the process. But the task is enormous. If Africa’s agricultural lands are to be saved, major efforts by the millions of people who live on the land will be needed.
The removal of trees and shrubs ranks as one of the most important causes of land degradation in Africa. New attention, therefore, has been focused on the role of trees in agriculture, as well as on the prospects of restoring soil fertility by combining trees and tree products with crops and livestock in integrated fanning systems—known as agro-forestry systems.
Agroforestry is everywhere in Africa. The main types include grazing or farming under savanna trees; growing coffee or cocoa under shade trees; planting fruit trees; sowing tree seeds on fallow land to speed up the restoration of fertility; planting “living” fences, windbreaks, or woodlots; combining trees, shrubs, and field crops in multistoried cropping systems; and growing crops between rows of nitrogen-fixing trees or shrubs (“alley cropping”). In these systems, trees play the role of “nutrient pumps.” Because their root systems are deeper than those of nonwoody plants, they bring to the surface nutrients that rains have leached down beyond the reach of other plants. The use of shrubs is also important, as they can yield fuelwood and fodder in less time than trees.
Agroforestry thus appears to hold out hope for reversing the processes of deforestation and soil degradation in Africa. For that reason, the World Bank recently evaluated experiences of farmers with agroforestry (see box) to answer the following questions: (1) Can agroforestry solve Africa’s environmental crisis? (2) Why do farmers plant trees? (3) Which agroforestry systems are most likely to be adopted by farmers? and (4) Who should take responsibility?
Scope of the study
The study looked at experiences with agroforestry in East and West Africa, including indigenous and innovative systems in three ecological zones: the humid lowlands, the semiarid lowlands, and the cool highlands. Seven cases in five countries (Kenya, Niger, Nigeria, Rwanda, and Tanzania) were selected for field research, representing a wide variety of agroforestry systems. In each case, researchers sought to understand how farmers perceived the proposed agroforestry system, how it fit into their normal production patterns, what demands it placed on their domestic resources, and what returns it could be expected to provide from the viewpoint of the farm household.
The study team identified some fundamental constraints that should be kept in mind when designing forestry projects:
• The “farm household” is not a single production unit; rather, household members (and in some cases, extended family groups) have different degrees of access to and control over resources, as well as different requirements for return on investments;
• Tree products play multiple roles in the domestic economy: as a source of food, fuel, building materials, craft materials, and specialty products for sale—such as medicinal leaves, bark, and roots;
• Individual rights to plant trees, collect tree products, and fell trees are often determined by customary laws and traditions, which may conflict with rights conferred under a formal legal system; and
• Trees, shrubs, and crop residues are part of a complex system of land management that sustains the separate but interdependent activities of agriculturists and pastoralists.
Answers to key questions
Agroforestry alone cannot solve the environmental crisis, but it can contribute to the solution. It can help to restore vegetative cover in areas where the natural forest has been almost entirely destroyed. However, it is unlikely to be widely adopted for fuelwood production, as long as wood can be collected from public lands at little or no cost. Thus other solutions must be actively sought to meet domestic energy needs.
Farmers plant trees for tangible benefits. Agroforestry has already been widely used by farmers for purposes other than fuelwood production, such as fruit, shade, poles, shelter, and restoration of soil fertility. Local markets for tree and shrub products are important, as these can provide a supplementary source of cash for producers. Agroforestry techniques are most likely to be implemented where farmers perceive that benefits will accrue within a short time frame, or where there are significant opportunities for off-farm income.
Farmers are most likely to adopt those systems that are congruent with local culture. Improving the use of indigenous trees is preferable to introducing exotic species, multipurpose trees are more acceptable than single-purpose trees, and fast-growing trees are more likely to be adopted than slow-growing trees. In areas of low population density, farmers appear more willing to adopt programs of passive protection for useful trees than to engage in active afforestation programs. In higher density areas, however, farmers are willing to invest substantial amounts of labor in order to gain the productivity-enhancing benefits of agroforestry systems.
Agroforestry extension should be integrated into the programs of national agricultural extension services. However, these programs should also be supported by forestry experts, who have technical knowledge of tree species, and by local nongovernmental organizations, which can help ensure project sustainability.
For more detail, see “Agroforestry in Sub-Saharan Africa” by the authors, World Bank Technical Paper No. 112 (1989). Copies available from the World Bank Publications Sales Unit, Washington, DC 20433, USA.