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close this bookAgroforestry in the West African Sahel (BOSTID, 1984, 82 p.)
View the document(introduction...)
View the documentAcknowledgements
View the documentPreface
View the documentOverview
View the documentChapter 1: Desertification in the Sahel
View the documentChapter 2: Traditional Land Use Systems
View the documentChapter 3: Uses and Potential of Agroforestry
View the documentChapter 4: Agroforestry Applications
View the documentChapter 5: Sahelian Agroforestry: Institutional Considerations
View the documentReferences
View the documentBibliography
Open this folder and view contentsAppendixes

Chapter 3: Uses and Potential of Agroforestry

As indicated earlier, the term "agroforestry" covers a variety of land use systems in which woody perennials are directly associated with agricultural crops and/or livestock in order to realize higher productivity, more dependable economic returns, and a broader range of social benefits on a sustained basis. Agroforestry can contribute to rural development in the Sahel by:

· Increasing the variety and stability of food supplies
· Providing a sustained supply of fuel wood
· Producing wood and a variety of other raw materials from shrubs and trees for construction, for farmer's subsistence, and to provide a constant supply of locally important "bush products"
· Protecting the productive potential of a given site and improving its environment and carrying capacity
· Safeguarding sustainability through appropriate intensification of land use, and improving social and economic conditions in rural areas by reducing risks and creating jobs and income
· Developing land use systems that make optimal use of modern technologies and traditional local experience and that are compatible with the cultural and social values of the people concerned.

In large but sparsely populated regions there is usually either no need or no possibility for intensive land cultivation. This has been, and in some areas still is, the case in the rural Sahel. In these areas, people have developed outstanding skills in exploiting available self-regenerating natural resources. They know the characteristics and products of most plants. In the Sahel, there are hundreds of species of trees and shrubs that are used in a variety of ways: for food, fodder, firewood, building poles, fiber for cordage, tannins, dyes, stains and inks, gums, resins and waxes, poisons and antidotes, and drugs for medicinal and veterinary purposes (see Chapter 2). In traditional subsistence strategies, woody plants were used effectively in combination with grasses and herbs and were kept in balance with the needs of wildlife and livestock, according to water availability and other local conditions.

With population growth, competition between farmers and herders has increased. Urban migration has created markets for food produced by proportionally fewer people. In areas where arable land becomes scarce, people turn to new land and more intensive practices. They try to accomplish this in two ways. One is through specialization, by crop monoculture, to achieve maximum yield of one product. Daily needs are met by exchanging or selling the surplus in order to obtain other goods and services. Alternatively, production can be diversified to satisfy most of the needs of a household or community. The bulk of production is locally consumed, and only small quantities are exchanged for goods not obtainable by other means. Although agroforestry is not necessarily confined to subsistence economies, it is clearly easier to meet the requirements of rural populations through a system of land use that integrates agriculture, pastoralism, and forestry than through monoculture. This is particularly true if natural sites and economic conditions such as infrastructure, access to markets, and purchasing power are marginal.


ECONOMIC BENEFITS

Crop yields in Sahelian countries are among the lowest in the world. Costs of agricultural infrastructure, fertilizer, and pesticides are among the highest and therefore are beyond the reach of most farmers. The attraction of agroforestry is in the greater potential stability of the system in responding to drought and heat stress, in its nutrient cycling and improved moisture balance, and in the greater variety of products it yields. In any given location, the type and extent of a suitable mixture of trees and crops will depend on environmental factors, such as soil type and rainfall, and on the purpose for which the crops are grown.

The following sections describe the potential benefits resulting from growing a combination of trees, shrubs, and agricultural crops.


Food

Agroforestry can increase the dependability of food supplies' thereby reducing risk in rural economies. As will be shown later, it also contributes to making the best use of scarce water resources. Under Sahelian conditions of extremely variable rainfall, risk is reduced by growing more vegetation per unit area compared with other systems, using mixtures of species, multistory structure, extending the growth period, and protecting and improving the soil. Trees and shrubs play an important role. Fruits and leaves of many species are edible and form part of the staple food of Sahelian people. They also are important sources of fodder for livestock, especially during the dryseason, and therefore indirectly contribute to food production through animal products. Similarly, agroforestry systems often provide habitat for wildlife and thereby increase the availability of bush meat. The many foods available from agroforestry systems can provide a more varied and potentially more nutritious diet.


Energy

Some families in the Sahel, particularly in urban centers, spend one-third of their income to buy firewood or charcoal. In others, one working day per week of one or two of the family members, often women and children, is spent collecting firewood from the open bush land, often located considerable distances from their homes. Field research in many parts of the Sahel indicates that, on the average, at least 1 kg of firewood is needed for the daily supply of one person. The actual amount of firewood or charcoal required is dependent, in part, on the inherent density of the wood, as heavier woods yield more energy on a per unit volume basis than lighter woods. Continued uncontrolled firewood collection results in severe destruction of vegetation.

The most severely affected areas are those in the zone between the Sahel proper and the savanna, where increased farming and herding have led to the greatest overuse of the vegetation. In the northern Sahel, the lower population density limits the degree of severity of deforestation; in the southern savanna region, rainfall is adequate to support a relatively plentiful supply of biomass fuel. Exceptions are the result of urban demand, which may extend for hundreds of kilometers as in the case of the charcoal supply for Nouakchott provided by the disappearing Acacia nilotica (gonakier) forests along the northern bank of the Senegal River.

Firewood plantations appear to have economic and ecological limitations in the true Sahel. Alternative energy supplies are not available or are too expensive. More than 90 percent of all household energy requirements are met by wood. Single tree or shrub cultivation, as applied in agroforestry and adapted to the environment, can make more firewood available to rural households.

Agroforestry satisfies other energy needs as well. Modern Western agriculture requires constant supplies of energy such as liquid fuel for mechanized farming, transportation, and production of mineral fertilizers. In Sahelian agroforestry, however, the need for mechanization is reduced, and the need for fertilizer can be met instead by animal manure, by mulching and composting of organic waste, and by nutrient cycling through deep-rooted woody perennials.


Renewable Raw Materials

Trees and shrubs are important sources of raw materials in the Sahel, since few others are available. Wood, in addition to firewood, ranks first; it is used in almost every aspect of daily life. Of these many uses, traditional building, fencing, and production of agricultural and household implements and furniture are most important.

Utility wood (predominantly poles, small logs, branch-wood for roofing, or thorny brush wood for fencing) is obtained through selective, single-tree utilization; thus destruction by clear felling rarely occurs. This highlights the possibility of producing wood on agroforestry land in single tree units that perform various productive and protective functions while they are growing.

In addition to wood, many other products from trees and shrubs are used locally and are even exported. The best-known product is gum arabic from the Acacia senegal, a small leguminous tree that grows in sub-Saharan Africa from Senegal to Somalia (Figure 5). It is currently among the most commercially important natural gums in the world. In addition to a broad range of domestic uses, gum arabic is used in the manufacture of medicine, chewing gum, confectionery, soft drinks, and a variety of foods. It is also used for printing in the textile industry. Although more than 80 percent of all gum arabic on the world market is produced in the Sudan, many Sahelian countries, including Mauritania, Senegal, Mali, Niger, and Chad, export smaller quantities and are making concerted efforts to increase their production. Gum arabic can be produced extremely well in agroforestry systems because the Acacia senegal integrates well with other crops and provides fodder for livestock. It has been traditionally used in this way for centuries in the drier areas of the Sahel.

Increasing the number, species, variety, and quality of trees and shrubs on lands formerly used only for rain fed agriculture or as pastures can improve the supply of many of these products. There is an outstanding demand for tree and shrub products both locally and for export because substitutes are not available, are too expensive, or because natural products are preferred.


Environment

When a natural ecosystem is replaced by one managed for subsistence or economic purposes, potentially competitive plants and animals are deliberately eliminated, while others disappear because of changed site conditions. As a rule in arid areas, having fewer species leads to greater risks to productivity because the simpler system is more vulnerable to drought, erosion, pests, and all the uncertainties of agriculture. Agroforestry, on the other hand, protects the environment by approximating the natural three-dimensional structure of a mixed tree/crop system and by maintaining or even increasing the number of plant species. Expensive failures of large-scale monoculture development schemes in the tropics, notably involving cotton and groundnuts in the Sahel, indicate that the kind of land use practiced successfully in temperate zones is not easily transferable. Agroforestry involves changes that benefit the farmer by substituting crops for natural vegetation, thereby reducing economic risks because the system can adapt to local conditions and generate a greater variety of products and resources.


SOCIAL BENEFITS

Agroforestry can help people to be more self-reliant by meeting daily needs through a more varied and often more productive economy, and by reducing the need to import food, fuel, fertilizer, herbicides, pesticides, fodder, building materials, and other products. It also enables rural Sahelian populations to relate economic production directly to their own cultural traditions and management capabilities rather than to alien perspectives and approaches to management, which are often insensitive to local needs, capabilities, and conditions. By increasing the self-reliance of rural populations and maintaining cultural continuity, agroforestry can help stabilize rural communities and reduce the destructive social anomie so often associated with rapid socioeconomic change. By simultaneously permitting increased production while relieving pressure on environmental systems, agroforestry also enables rural populations to maintain or restore the traditions of environmental stewardship so basic to the long-term well-being of the Sahel region.


FLEXIBILITY

Soils and vegetation in the Sahel vary, even over short distances. The great variety of sites has, in the past, too often been disregarded in development projects. It is nearly impossible for people unfamiliar with the region to detect site differences during the long, dry season. As indicated in the example of agriculture in the Yatenga region of Upper Volta (Chapter 2), however, site quality has always been carefully respected by local farmers and herders.

Agroforestry combines plants and animals that are well adapted to varying site conditions. Existing vegetation may serve as an indicator in the selection of more productive species to meet local needs. Unfortunately, however, knowledge about effective plant associations in agroforestry generally is quite limited. Research in this area has been neglected compared with research on conventional cropping systems because of the emphasis placed on improving productivity of good agricultural land in order to feed larger numbers of people. The associations among plants in agroforestry systems are more complex, and the research is more difficult and time-consuming because of the relatively long life of the perennial species involved.

The Sahel is not suited for true forest. Growing large, closed forests is probably not possible with the region's limited rainfall; however, selected trees and shrubs (or small groups of them) can be grown successfully on soils suitable for their specific nutrient and moisture requirements. The same holds true for agricultural crops.

The sustained and multiple use of seasonally flooded depressions and areas with adequate ground water availability appears widely neglected. Although these seasonally flooded depressions are used for watering cattle during the Sahelian rainy season, they could be converted into small "agroforestry oases" with an upper story of multifunctional trees and a lower story of agricultural or horticultural crop plants. Several areas with satisfactory ground water recharge, such as the Bahr al-Ghazal depression of Chad, could support higher levels of agricultural production.

Agroforestry is extremely flexible in its adaptability to ecological niches; and, because of its diversity, it does not impose heavy pressure on specific sites. Beyond the traditional knowledge of local farmers, herders, and other experts in land use, much remains to be improved through trials and experimentation. Each system of agroforestry, with interactions between plant associations and their individual components, is faced with the problem of competition among and within species. The goal of agroforestry is to reduce this competition by optimizing combinations of agriculture, pastoralism, and forestry over space and time.

Correlations between optimal and minimal population densities and sizes of woody as well as annual plants need to be quantified. Some work has already been done on optimum tree spacing and mean annual rainfall, which will help to develop relevant land use techniques with variable numbers of individual trees. Minimum factors for plant growth show a certain intraspecific variation. This offers an opportunity to optimize plant associations.

Agroforestry also offers techniques to make optimal use of land on a small scale. There are many interdependencies among plant and animal species to be considered. All animals and man depend on plant biomass production through photosynthesis. Many woody plants depend on rhizobial bacteria or mycorrhizal fungi; others are parasites, saprophytes, or climbers. The food preferences of various forms of livestock are generally complementary--some being primarily browsers, others being preferential grazers. The productive potential of adapting plant and animal species to particular sites in the Sahel has not yet been adequately exploited.


ACCEPTABILITY

Agroforestry has been defined as a sustainable land management practice that increases the overall yield of the land, implying management strategies compatible with the cultural practices of the local population. Agroforestry can be improved by new techniques such as irrigation, fertilization, and subsoil treatment, and particularly by selecting and breeding more productive economic species. Local species should be given preference because they are adapted to the sites and their uses are well known to the people; however, exotic species may have attractive production capabilities in the new environment.

The belief that Sahelian people tend to be conservative, if not entirely against all innovation, is not true. There is, in fact, ample evidence of change. For example, when it is said that nomads continue to enlarge their herds irresponsibly, only for purposes of prestige, this is only a half truth from an external perspective. For the nomad, a large herd composed of animals of all ages will have a larger number of survivors after a period of drought, giving more security to the herd's owner. Similarly, a farmer who has many children and, during years of high rainfall, extends his fields into rangeland areas or around a water hole (thereby giving his cattle access to water), is trying to reduce the risks of harvest failures and lack of grain. It is also true, however, that these strategies often result in increased environmental degradation. Greater effort must be made to reconcile changing local needs and practices with sound environmental management.

Another especially relevant aspect of land use in the Sahel is that in the present and at least for some future decades, prevailing conditions in the Sahel set definite limits to growth. Although very substantial increases may be possible in specific locations and in selected sectors, higher agricultural yields should be only one among a number of strategies to increase human ecological carrying capacity. Others would include:

. Improving the quality of the products (for example, higher nutrient content and better digestibility of crop plants, higher yield or value of cash crops)

. Saving scarce resources (for example, by introducing fuel-efficient stoves, less wasteful charcoal-making technologies, and water-saving trickle irrigation)

. Substituting deficient items with those more readily available (for example, living fences and hedges for barbed wire or wooden fences; compost and mulch for imported fertilizers).

These measures will involve making resources available to the local farmers and herders beyond usual agricultural or forestry projects. While this may appear to be a handicap that retards progress, it is, in reality, a multiple-strategy approach based on the way people see their problems and on the way they are accustomed to addressing necessary changes.