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Desertification in the Sahelian and Sudanian zones of West Africa

Jean Gorse

Jean Gorse is head of a World Bank working group on desertification in West Africa. This article includes contributions by Yvon Dommergues, Robert Fishwick, Willem Floor, David Steeds and James Thomson.

Interactions between droughts and human abuse of the environment are the primary cause of the current crisis in the Sahel, Jean Gorse argues. Based on an extensive new study undertaken by the World Bank, the article offers a series of very specific prescriptions - many of them controversial - for alleviating the Sahelian crisis. Unasylva is devoting an unusual amount of space to this article because of the urgent need for action in the Sahel - a need underscored by FAO's own emergency programme for Africa; because forestry clearly has an important role to play; and because the recommendations contained here are likely to stimulate productive debate and discussion about the problem.

· The Sahel is often viewed as an area isolated from the surrounding region, and with its own special problems. But on ecological grounds, as well as for historical and contemporary political and economic reasons, the Sahel should instead be seen as the northern part of a larger regional whole which includes the more humid Sudanian zone. The focus of this article is, therefore, on the West African Sahelian and Sudanian zones (SSZ).

Within the SSZ, this article concentrates on seven countries: Burkina Faso, Chad, the Gambia, Mali, Mauritania, the Niger and Senegal. These countries are grouped around the fourteenth parallel; all are members of the Permanent Interstate Committee for Drought Control in the Sahel (CILSS). While the northern areas of Benin, Ghana, the Ivory Coast, Nigeria, the Republic of Cameroon and Togo lie within the SSZ, they are not treated explicitly here for reasons of comparability of statistics. Cape Verde, the eighth member of CILSS, has been excluded from this analysis because its island situation gives it a quite different environmental character.

Physical features

The seven continental CILSS states cover 5.3 million km², of which two-thirds are north of the northern limit of rain-fed cultivation. Throughout the remaining area, too, evapo-transpiration exceeds rainfall during most months of the year. Only one rain-fed crop per year is possible without irrigation. The climate is harsh indeed: a short rainy season characterized by often violent and unpredictable showers, followed by a long dry season. The dry season is hot, but the first few months following the rains are perceptibly cooler. This "cool dry season" creates problems for irrigated crops: rice must be planted so that germination occurs before the temperature drops, but the season is not usually cool enough to guarantee a wheat crop.

Of the 530 million ha under discussion, soils are suitable for cultivation on only about 60 million ha, of which about 20 percent were being farmed in the 1970s. About 150 million ha are classified as range land.

Most SSZ soils are of low fertility, particularly poor in phosphates and nitrogen, and structurally fragile with low humus content and reduced water-retention capacity. Hydromorphy, hard clay pans, laterization, and wind and water erosion are all common problems. Research and experience over the past 20 years in SSZ agriculture and forestry tend to confirm that the low fertility and vulnerability to erosion of SSZ soils are as important a constraint on plant productivity as drought (Breman and de Wit, 1983).

Water for perennial or seasonal irrigation is available in abundance from major streams and rivers (the Senegal, the Niger and the Chari-Logone). Uncontrolled irrigation and flood recession cropping are widely practiced, but the area equipped for partially or fully controlled irrigation is still scarcely 100 000 ha. Bottomlands, small streams, lakes and shallow groundwater tables provide locally important sources for dry-season cropping. The shallow aquifers, which are also the principal source of village water supply, depend for recharge on both rainfall and sound resource management, particularly of the natural vegetative cover, in order to reduce surface water run-off and promote infiltration. No systematic work is known to have been conducted on the effects of the current dry period on groundwater reserves, but all recent indications, however sketchy, show that shallow aquifer levels are falling perceptibly.

West Africa - Climatic zones

The natural vegetative cover - forests, woodlands, tree/shrub/grass savannahs and steppes - is relatively drought-resistant and well adapted to the ecological conditions of the SSZ. In the context of traditional production systems, people have selected and developed multipurpose plant and tree species, and productive, anti-erosive vegetative associations such as bush fallows, forest parks and live fences. Much of the tree and shrub cover is composed of slow-growing species. These are often difficult to regenerate where mature stands now exist, because local conditions have deteriorated. Prolonged dry periods, combined with increasing human and livestock population pressure, further retard already slow natural regeneration and thus trigger new phases of the desertification process. The natural forest cover still provides the overwhelming source - 85 percent (CILSS, 1983c) - of domestic energy, in addition to building-poles, timber, and secondary forest products and foods, but access to these products is fast becoming more difficult.

The anti-desertification effort should focus on the most threatened area, the narrow Sahelo-Sudanian heartland, and not, as sometimes suggested, on the desert fringe.

SSZ pasturelands are estimated at 150 million ha. Patchy, uncertain rainfall makes it difficult to predict locations of good pasture in a given year, although overall carrying capacity can be roughly estimated. In most of the rangeland in the Sahelian and Saharo-Sahelian zones, annual grasses now predominate, having replaced the more valuable but less resistant perennials. Annuals may not appear for years in an area for lack of adequate moisture, and then produce a flush of good forage when the rains strike again. Perennial grasses mixed with shrubs and trees, particularly in the better-watered bottomlands, are still to be found in the Sahelo-Sudanian zone in relative abundance. Overall, however, the situation of the pasturelands is one of deteriorating quality, quite apart from localized problems of acute overgrazing.

Drought, desertification and population

Drought will be defined here as a markedly below average amount of rainfall during a year or series of years. Precision in this regard - how much less rain - is difficult to provide for two reasons. First, averages are deceiving, particularly in the northern arid areas, where precipitation totals vary markedly from one year to the next. A few years of abundant precipitation often skew statistical averages well above realistic expectations of rainfall in a given place in, for instance, seven out of ten years. Second, gross amounts of rainfall only partly determine vegetative productivity. In addition to soil fertility and structure, the timing and distribution of precipitation play a crucial role. "Below average" rainfall, if well distributed temporally and spatially, will produce quite adequate crop yields.

Drought is a constant menace, a fact of life with which rural people must cope if they are to survive in the region. But drought alone does not, in the short run, produce resource degradation of the sort now found in the SSZ. Other factors are at work, including population growth, the spread of extensive agriculture and thus deforestation, and rapid urbanization (which concentrates demand for fuelwood). In addition, changes in national and local political, economic and social institutions have on balance reduced local autonomy and capacity to organize joint undertakings. Together, these factors are making it increasingly difficult to manage the natural resource base upon which the economy of the region rests.

Desertification can be defined as follows: "the continuous and sustained decline in the amount and quality of the biological productivity of arid and semi-arid land. Such stresses, if continued or unchecked over the long term, lead to ecological degradation and ultimately desert-like conditions. Biological productivity refers to the naturally occurring plant and animal life as well as to the agricultural productivity of a given area" (adapted from, Sabadell, 1982). Common indicators of desertification include a reduction in the amount and diversity of plant and animal species, loss of water-retention capacity, lessened soil fertility and increasing wind and water erosion. Eventually, plant and animal communities become so radically simplified that species formerly common in an area can no longer survive under the drastically altered circumstances, even if they are deliberately reintroduced.

Desertification takes two distinct forms: desert spread, and induced desertification in more humid areas. Saharan encroachment into Sahelian lands may occur gradually through growing aridity and resource abuse. Of more immediate concern here is human-induced, accelerated degradation of areas well south of the Saharan fringe. Deteriorated patches occur now with alarming regularity around centres of human activity, even well south into the Sudanian zone. In their struggle to survive, populations further overexploit resources in these focal points of desertification and gradually encourage their spread. The challenge is not "stopping the desert's advance from the north", but effectively managing renewable resources south of the desert.

SAND-DUNE FIXATION IN SENEGAL attempting to halt desertification

Is desertification caused by drought or by resource abuse? The answer to this fundamental question depends upon perceptions of drought and the destruction of resources with which it is often associated. Three general explanations are advanced:

· First position. Drought in the SSZ is an overwhelming, long-term phenomenon in which people play no part. Increasing aridity will inexorably destroy vegetative cover. Desertified areas will spread to engulf and obliterate what are already marginal environments of limited productivity. Resistance to desertification is futile.

· Second position. Drought in the SSZ is a short-term, recurrent phenomenon, again independent of human influence. Resources suffer in the short run, but when a drought of five years' duration or less ends, local production systems sooner or later recover. In any case, droughts of this sort can be endured, especially if food reserves exist in amounts adequate to tide people over periods of low output. Emergency food aid is a further recourse.

· Third position. Desertification is a complex process caused apparently by interactions between drought and human abuse of the environment. Better natural-resource management could mitigate the impact of even serious droughts, although decades-long droughts like the current one could alter the natural resource base profoundly.

This article takes the third position, for two reasons. First, while the available evidence indicates that drought has long played a role in SSZ ecology (National Academy Press, 1983a), past periods of short- to medium-term aridity have had little permanent effect. On the other hand, severe drying trends lasting a century or more unquestionably did modify the natural vegetative cover. During the modern era, however, when droughts of two decades or less have been the rule, much resource destruction has occurred at the hands of human users, whose numbers have increased far more rapidly than before.

Second, whereas climate is a given, human behaviour can be modified in response to changes in the environment. The desertification process is slow and insidious, and governments and rural communities have consequently been slow to react, despite the rapid growth in population. So long as there are unexploited techniques and more appropriate organizational arrangements and policies for encouraging better management of the environment, it would be shortsighted to ignore them by assuming, on uncertain evidence, that the principal cause of desertification is climate. The problem of desertification is nonetheless severe, since it is an example of conflict between public long-term resource use and private short-term resource abuse. If there is no effective reconciliation between these two interests, the process of desertification will continue; while the process can be arrested, the end-result is irreversible. Drought, if not prolonged, does not, by itself, pose an enormous threat to the long-term viability of rural production systems in the SSZ. But it accelerates the negative consequences of resource abuse. Overuse of one renewable resource, in turn, often reduces the viability of others, and this negative dynamic intensifies when drought periodically strikes an area. This point can be easily illustrated. The spread of rain-fed, extensive agriculture into forest, bush and pasture areas reduces the total forage available to transhumant (seasonally grazed) livestock, particularly when, as now, farmers and breeders increasingly collect and stock crop residues to carry their own animals through the dry season. When drought strikes, transhumant pastoralists do what they can to save herds. Lacking alternative forms of forage, they try to increase their animals' intake of browse. They vigorously lop trees already weakened by lack of soil moisture. Many trees die as a result of this abuse. Pressure then intensifies on the remaining wood stock during the next drought. Clearing fields for animal traction or machine cultivation may disrupt existing soil fertilization cycles based on nutrients that in-field trees return to the soil surface in the form of humus. If these organic nutrients are not replaced by organic or chemical fertilizers, crop yields decline. Stripping trees from fields also reduces the wind-break effect that even an open canopy can provide, and increases wind erosion. When fields are fallowed, in those systems where people/land ratios still permit it, natural regeneration occurs much more slowly. In the meantime, soils may suffer both wind and water erosion.

Whereas climate is a given, human behaviour can be modified in response to changes in the environment.

Population. Total population in the SSZ countries was estimated at 31 million in 1980. Overall densities remain low: 6 persons/km² for the entire area and roughly 15 persons/km² if the Saharan and Sahelo-Saharan zones are excluded. Densities can, however, reach 100 persons/km² in some areas, visibly overtaxing their carrying capacity. The average density in Senegal is now 20 persons/km² The lowest national density is found in Mauritania, with 1.5 persons/km² and the highest in the Gambia, with 60 persons/km² Population growth rates between 1980 and 2000 are expected to be about 3 percent annually. On this basis, the area will have 75 percent more people by the year 2000, or 54 million inhabitants. In 1961, by contrast, the population was 19 million.

It is clear, however, that people are increasingly moving away from the most densely populated areas to more promising areas in the Sudano-Guinean zone.

According to the ecological classification established by M. Keita, the SSZ population in 1980 was remarkably unevenly distributed (FAO, 1982). While 80 percent of the people lived in 25 percent of the total area south of the Sahelian zone, fully 40 percent lived in only 6 percent of the total area. Furthermore, in the subzone comprising the Senegalese groundnut basin, the Gambia and Burkina Faso's Mossi plateau, fully 24 percent of the total population lived in only 2 percent of the total area; population density there was 60 persons/km², with the rural population at 45 persons/km². Such concentrations of demand for arable land and fuelwood lie at the root of resource abuse. It is in these areas that patches of desertification are most clearly visible; they will spread rapidly if resource management measures are not implemented.

Urban population growth rates reveal an even more volatile situation. Urban populations averaged 22 percent of national populations in 1981 (lowest: Burkina Faso, 11 percent; highest: Senegal, 34 percent), but urban populations now grow at an average rate of 5 percent annually. Mauritania - arguably the country that has suffered most from the impact of drought over the past two decades - has experienced an 8.6 percent urban population growth rate in recent years. Senegal, with one-third of its population already urbanized, has the lowest urban growth rate at 3.3 percent. Migration within rural areas is also a growing phenomenon, although figures are scarce. It is clear, however, that people are increasingly moving away from the most densely populated areas, notably the Mossi plateau and the Senegalese groundnut basin, to more promising areas in the Sudano-Guinean zone.

Two important observations emerge from these figures. First, when population grows at 3 percent annually, total population doubles every 25 years. The ballooning demand for resources that this growth represents almost inevitably generates extensive resource abuse in the short run. Adjustments are not made quickly enough to these changing conditions: consumption accelerates, but at the cost of overexploitation or "mining" of the resource base rather than investment in its improvement or even sustenance. The desertification process takes hold. Second, the destruction of the rural environment will almost certainly result in further uncontrolled urbanization, compounding the problems of already strained municipal administrations.

Traditional production systems

Traditional production systems have been tailored very precisely over time to contend with particular circumstances. The following three basic systems, which can even coexist in the same area, illustrate the range of approaches rather than the richness of any one system. Traditional production systems merit attention because they permit fairly large populations to exploit marginal regions in a sustainable manner.

Agrosilvicultural. Variations on this system are practiced by the Hausa of Nigeria and the Mossi of Burkina Faso, among others. Production is based on rain-fed agriculture in association with trees and shrubs. The system involves the cultivation of several main plant species (such as millet and sorghum) as food crops, and cotton for cloth. Secondary products are obtained from the systematic exploitation of natural vegetation (trees for fruits and leaves as well as firewood and building-poles, bark for cord and medicine, thorn branches for fencing, grasses for thatching, fodder, green manure, etc.). Small ruminants, particularly goats, often play a major role. Production in the agrosilvicultural system is concentrated during the two- to four-month rainy season, individuals, particularly adult men, often travel during the long dry season in search of temporary work.

Traditional production systems were not just technical systems; perhaps more important, they were managed by local authorities.

Trees in this system meet not only consumption demands but also, in bush fallow and open field sites, other needs. If grown in sufficient numbers on fields, they protect exposed soils against wind and water erosion and also regenerate soil fertility by recycling subsoil nutrients as green manure in the form of leaves. Micro-organisms associated with root systems, such as nitrogen-fixing rhizobia and mycorrhizae which improve plant feeding, can also increase the growth of certain species.

CATTLE IN THE SAHEL overgrazing speeds destruction

Agrosilvipastoral. Variations include those practiced by the Senegalese Serer, the Nigerian Bugage and the Malian Soninke societies. This system relies on the sort of field crop/tree/shrub associations characteristic of the agrosilvicultural system but integrates livestock production to reinforce soil fertility, as well as for market sale. This system puts a premium on trees that produce browse or seed pods suitable for fodder. Trees may also be exploited commercially, for gum arabic (Acacia senegal), shea-butter (Butyrospermum paradoxum) and other marketable food products, as well as for firewood and building materials.

Livestock in such systems must be accommodated during the wet and dry seasons by carefully defined access to fields, as well as to surrounding bush and pasture areas. When people are cultivating field crops during the rainy season, animals must be stabled or herded elsewhere. During the dry season, after the harvest has been stored, herded or free-ranging animals can roam fields to forage on crop residues. In those systems based on systematic manuring, stock owners tether their animals (or the herder stables them) in fields at night: the concentration of droppings increases soil fertility. In the past,.however, these systems rarely undertook systematic composting of manure mixed with straw or stalks.

A DESPERATE NEED FOR TREES using every bit of an Acacia albida

Silvipastoral. SSZ silvipastoralists - the Fulani, Tuareg, Mauri and Teda peoples - keep cattle, camels, sheep and goats. Ethnic groups and individuals within them tend herds of different species, sex and age composition. The majority specialize to some extent in one species or another and occupy environmental niches that meet the needs of their particular herd. Most within this group are transhumant pastoralists. Herders operating under normal conditions move within clearly defined ranges; usually, a group has both wet- and dry-season "home" pastures.

The driving force behind these annual displacements is the need to find forage for the herd in all sea sons. Most forage - pasture grasses, shrub and tree browse, and crop residues - appears irregularly in time and space. Herders typically congregate during the wet season in the Sahelian and Saharo-Sahelian zones, when rains usually produce grasses and accumulations of surface water on the desert edge. The abundance of food and easily available water lasts only a few months, typically from July through September/October. Thereafter, until the next rains eight or nine months later, pastoralists depend on well-water for themselves and their stock. Some seasonal watercourses and a few perennial rivers provide water for longer periods for some groups.

In the silvipastoral system, trees are a critically important fodder source during the dry season. When the rains cease, grasses dry out and lose most of their nutrients. They still provide the bulk needed for ruminant diets, but vitamins, digestible proteins and minerals must come from other sources (National Academy Press, 1983b). Traditionally, tree and shrub browse has provided these elements.

Common features. In most traditional production systems, deliberate tree-planting never became a significant activity, since most areas enjoyed a surplus of natural forest cover. Selective cutting and management of the regeneration of natural forest cover, however, often produced stands of preferred tree/shrub species in the fields. Certain trees and shrubs were also preserved in bush stands and served as the basis for restoring soil fertility on fallow lands. Under these systems, humans protected trees, shrubs and bushes useful for many purposes, and not just for browse, building materials, fuelwood and nutrient recycling. The fruits, gum, honey and medicines they provided all justified the protection of certain woody species. This deliberate plant selection has resulted in a large number of specific and valuable associations throughout the SSZ. Farming under a selected forest park canopy is perhaps the most visible example of this sort of activity.

These were not just technical systems; perhaps more important, they were managed by local authorities. In this sense, they were participatory, although not necessarily democratic; at least there were no top-down prescriptions emanating from a distant agro-bureaucracy.

Carrying capacities. The carrying capacity of a natural system can be expressed as the amount of biological matter the system can yield (for consumption by animals, humans, etc.) over a given period of time without impairing its ability to continue producing, or the number of organisms it can support without being degraded (Webb and Jacobsen, 1982). Since carrying capacity will vary as a function of technology, the level of technology has to be specified.

The rural population of the SSZ that can be sustained by traditional agricultural and livestock systems is 36 million, or considerably more than the 1980 rural population of 27 million. By contrast, the total population sustainable on the basis of fuelwood from the natural forest cover is only 21 million, whereas the 1980 total population was 31 million. For all the imperfections in the data, these two broad findings are defensible. The orders of magnitude of sustainable and actual population densities are given in Table 1.

However imperfect the data base and the presentation by zones, which necessarily conceals differences within zones, three general observations are suggested by these figures:

· In all zones, the carrying capacity of the natural forest cover is lower than that of crops and livestock with traditional production techniques. The natural forest cover is therefore the most vulnerable part of the ecosystem; indeed, in five of the six zones, the actual population already exceeds the sustainable population. The natural forest cover is not just vulnerable; it is already being severely overexploited.

· The actual density greatly exceeds sustainable density in three cases: fuelwood, and crops and livestock in the Sahelo-Sudanian zone, and fuelwood in the Sahelian zone. These are clearly the zones most vulnerable to the desertification process.

· · The anti-desertification effort should focus on the most threatened area, the narrow Sahelo-Sudanian heartland, and not, as sometimes suggested, on the desert fringe. But in the heartland, the scope for intensive production is much more limited than in the southern Sudano-Guinean zone. The anti-desertification effort should therefore be twofold: first, in the heartland itself, specific anti-desertification measures as well as any intensive production techniques that may be profitable should be undertaken; and second, in the Sudano-Guinean zone, existing, spontaneous settlement by people from the heartland should be further encouraged despite difficulties encountered.

Table 1. Sustainable and actual population densities (People per km²)


Sustainable population:

Actual rural population

Sustainable population fuelwood

Actual total population














































Note: Bold type indicates arena where actual population already greatly exceeds sustainable population.

Past development activities

Although development efforts have been organized along sectoral lines - agriculture, livestock or forestry - they nonetheless share certain weaknesses. In particular, planners have often misunderstood the logic of traditional production systems, and they have thereby overestimated the ease with which improvements could be introduced and underestimated the negative consequences of intended improvements. Planners seem to have neglected the fundamental significance of rainfall variability and risk-avoidance in all SSZ production systems.

One of the reasons for the failure to understand traditional production systems was that the practitioners of such systems were seldom consulted in a participatory fashion. Indeed, lack of participation on the part of the ostensible beneficiaries has been another common weakness of development activities. Supposed beneficiaries usually have little input in to the planning process, and project design suffers in consequence; nor are their views regularly solicited, and acted upon, during implementation. The old political adage that "those who can't say no, have no say" applies.

A third common weakness has been the underestimation of (a) the managerial weaknesses of existing institutions and the difficulty of setting up new institutions, and (b) the remaining strengths of local institutions. In fact, few attempts were made to investigate the organizational bases, capabilities and limits of local institutions, particularly where cooperatives existed, since they were often assumed to be synonymous. More recently, however, dissatisfaction with the agro-bureaucracies has spurred interest in local groups as retailers of inputs, managers of credit, and organizers of primary marketing. Supported by adult literacy campaigns, many promising initiatives are now under way.

Table 2. Relation between actual rural population (RP) and carrying capacity (CC), by zone




Sudano-Guinean, Sudanian, Saharan. And parts of Sahelo- Saharan and Sahelian

RP slightly > CC

Sahelian, Sahelo-Saharan, and parts of Sudanian

RP greatly > CC

Sahelo-Sudanian, and parts of Sudanian and Sahelian

Forestry. Forestry departments were first set up in the 1930s and, until recently, their main activity was the demarcation and policing of forest and fauna reserves. These reserves were set up primarily in the Sudano-Guinean zone, where land was relatively abundant, and particularly where diseases such as river blindness and sleeping sickness hampered settlement.

In the last decade, several pilot reforestation plantations have been initiated, mainly in the Sahelo-Sudanian zone, where the natural forest cover is being most rapidly depleted. Although no inventory has yet been made, it is already clear that the results are disappointing, not least because these operations were based on production techniques developed in the Sudano-Guinean zone. In fact, very little research has been done in the drier areas, and there are today no technical packages really adapted to the harsh conditions of the Sahelo-Sudanian zone or further north.

In the last few years, work has begun on the management of the natural forest cover, and the promotion of in-field natural regeneration and community and family - based plantings. Although it is too early to draw conclusions, the initial results are not as cost-effective as anticipated.

Although long established, forestry departments remain weak institutions in SSZ countries; forestry appears to be a postponable undertaking and therefore gets shortchanged in the competition for budgetary resources. Perceptions may be changing, however, as suggested by recent conferences in the Niger and Senegal. Other perceptions must change too, for there is a strong preference among foresters for exotic tree species for wood rather than indigenous multipurpose tree species. Increasing evidence suggests, moreover, that farmers rarely perceive the utility of tree planting for wood as distinct from the need for many other forest products.

A better resource management strategy

A holistic design approach based on participation is necessary to development work, both because of the complexity of the problem of managing the fragile resources of the SSZ and because research has clearly shown that farmers and pastoralists do indeed take a comprehensive approach to the natural resources on which they depend.

A probable-outcome approach to the design of technical innovation is necessary, since contending with dry years is a major preoccupation of SSZ peoples. Benefit-cost ratios of 2.5:1 in "average" years may simply not be sufficiently attractive in the light of the probability of bad years. Fertilizer that can be applied as a top dressing, after a crop has been established, will be more readily adopted than fertilizer that is to be applied as a base dressing, before planting.

However fragile the data base, the ratio of actual population to carrying capacity under traditional production systems is a useful tool for assessing possible actions. Specific action programmes will have to be site-specific, since people's interests, aspirations and readiness for collective action are not identical and the physical conditions, even in apparently homogeneous areas, are not uniform. The following discussion illustrates possible actions by reference to the three types of ratio between rural population and carrying capacity; throughout, it is important to bear in mind that (a) both production potential and rainfall reliability decrease toward the north, and (b) although carrying capacity is not a static concept, it is only in the Sudano-Guinean zone that there is, today, any proven scope for increasing it.

Where rural population is less than carrying capacity. In areas where rural population is less than carrying capacity, everything is to be gained by increasing population. Not only is there excess capacity under traditional production systems, but there is also great scope for increasing capacity by more intensive methods. In the north, however, the most effective approach to maintaining renewable resources will be to rely on traditional production systems and to strengthen local organizations. In the present state of knowledge, the scope for actually increasing carrying capacity is negligible, but two ideas are worth pursuing:

· Improvement of bush fallows. The main goal of fallowing is to promote natural regeneration as rapidly as possible, both to protect bare soils against erosion and to re-establish fertility. The greatest returns to fallowing, measured by regeneration of fertility, occur in the first five years (Gorse, 1973). If this period could be shortened by providing ground cover (reseeding and nitrogen fixing), carrying capacity could be increased.

· Forest parks - trees interspersed as a protective canopy with crops - are a common feature of traditional production systems. These could be rendered more productive by the introduction or reintroduction of noninvasive, multipurpose trees like Acacia albida.

Forestry plantations are conceivable wherever rural population does not exceed carrying capacity, but the practical possibilities are extremely limited since several conditions must be met. In the south, the three conditions to be met are as follows: (a) transport costs from plantation sites to consumption centres must be acceptable; (b) soils must be of at least fair quality (and poor soils may be the explanation for low population in specific sites); (c) such plantations must be developed with the consent of neighbouring people, lest there be such costly reactions as "accidental" fires in the plantations. It may be possible to buy the acquiescence of the local people by creating jobs related to the plantations or to force compliance through strict policing, but both these solutions will involve considerable costs.

Where rural population slightly exceeds carrying capacity. In areas where rural population slightly exceeds carrying capacity, and thus where land has supplanted labour as the major constraint, more intensive production will be more profitable. But the rainfall zones in which these areas are located do not have high potential, and the evidence suggests that cash inputs are just not sufficiently profitable in comparison with the reduction of fallow. In the meantime, exhortations to intensify production are futile, and the accompanying agro-bureaucracy is a waste. If the carrying capacity cannot be increased, at least its decline can be arrested; this can be attempted in a number of ways, with the main focus on increasing soil moisture storage capacity:

· bunding and rock-terracing, and other elementary anti-erosion measures;

· green manuring and use of animal manure, provided it is possible to get the organic content up to some significant level (1-2 percent) and keep it there;

· improvement of bush fallows, where they still exist;

· improving wells and well networks to facilitate grazing on under-exploited dry-season pastures, provided such under-exploitation is verified and such improvements are coupled with locally run systems;

· forest parks, but also live fencing, promoted by mass rural forestry actions;

· revision of the forestry code to remove disincentives to the planting of currently protected species;

· participatory management of the natural forest cover to promote complementary rather than competitive exploitation of the wood stock; this would include organized harvesting by cutting, pollarding or coppicing trees and lopping branches during the period just before the rains, when the sap has begun to rise in most species, in order to promote rather than hamper natural regeneration.

EVERY TREE IS AN OASIS a critical factor is carrying capacity

Where rural population greatly exceeds carrying capacity. In areas where rural population greatly exceeds carrying capacity - where the land constraint is overwhelming - anything that can increase land productivity should be readily adopted. The fact is that overall land productivity is declining, which simply means that the available intensification techniques are just not sufficiently profitable on a wide scale. Faced with this fact, people are opting to move away, notably from the Mossi plateau and the Senegalese groundnut basin. But even in these areas, the total rural population is still increasing, and resource capital is being consumed for short-term survival.

In these areas, the task - and it is a formidable one - is simply to arrest the decline in carrying capacity. In some localities, where local organizations are or can be made effective, small watershed management plans could be executed and maintained satisfactorily. In other areas, bunding and terracing at least could be promoted, also with some public support. More generally, however, individual actions are likely to be easier to promote than group activities.

· Manuring and mixed farming. Keeping livestock in densely settled regions will increasingly require stabling and the provision of fodder and feed supplements. Training in these techniques should pay off. The efficient use of manure, through additives and composting, could also benefit from training efforts.

· Intensified cropping. Although the record is not encouraging on a wide scale, there are impressive pockets of intensive farming. Elimination of any negative distortions in input and output prices can only encourage more intensified farming, but the scope for such corrective policies in the SSZ countries is more limited than is commonly supposed. Vegetable and fruit farming is already well developed around cities as well as in certain quite remote areas. Such intensive production will be limited by the domestic market until more vigorous efforts are made to develop markets in the coastal cities and, possibily, in Europe.

· Forestry. In the densely settled areas, forestry will have to be modelled on the "four around" planting approach, in which every space available to support a tree is used. In some areas, local people have already gone some distance in this direction. Faster-growing and more drought-resistant stock, engineered through innovative techniques, should meet with good demand in many areas.

Table 3. Actual and sustainable numbers of people (Millions)




Sustainable population

Actual rural population

Sustainable minus actual population

Sustainable population*

Actual total population

Sustainable minus actual population


















































Reducing demand

Population. Current population growth rates clearly cannot be sustained for very long without a deterioration in living standards - unless there is a dramatic improvement in rural productivity, or non-rural (or foreign) employment opportunities. The magnitude of the problem is best grasped by expressing the comparison between actual and sustainable populations in terms of numbers (see Table 3).

Quite apart from the already overburdened fuelwood resources, the apparently comfortable margin of 9 million people in farming is deceptive. Even if the rural population increases by only 2 percent per year, it will exceed 40 million in the year 2000, as against a total sustainable rural population of 36 million. The latter figure does not take account of proven productivity gains obtainable in the Sudano-Guinean zone, but nor does it take account of the declining productivity in the already overpopulated zones or the tsetse-fly constraint on livestock in the Sudano-Guinean zone.

Although long established, forestry departments remain weak institutions in SSZ countries

Resettlement has a long tradition in the SSZ countries. Today, the number of people involved in spontaneous migration into the Sudano-Guinean zone, although this is a phenomenon little known or understood, far exceeds the number of people being resettled under government-sponsored schemes. Such schemes have proved costly in terms of the number of families settled, and may not even have had any net effect on the total number of settlers. On the other hand, spontaneous migrants tend to destroy vegetative cover unnecessarily, thereby undermining the more cautious approach to resource husbandry of long-term residents. Given these problems, but also the unquestionable potential of the Sudano-Guinean zone to relieve population pressure further north, at least for the next two decades, it is surprising that settlement policies have not attracted more attention; nor are they even high on the policy agenda today. Here is a real challenge to governments and the donor community - to find answers to the following questions:

· What sorts of readily enforceable land-use regulations should be put in place to promote sustainable settlement in those parts of the Sudano-Guinean zone to which spontaneous migrants are moving?

· What further role, if any, can the public sector usefully play to encourage settlement into the Sudano-Guinean zone? How far can assurances be given, in the context of a land-use planning approach, that the location of investments in roads, wells, medical facilities and schools would be selected to favour areas subject to spontaneous immigration?

Wood. The SSZ countries are already consuming far more than the total fuelwood output of the accessible natural forest cover; they are rapidly cutting into the capital stock of trees, and this is true in every zone except the Sudano-Guinean. The effects are most clearly in evidence in the vicinity of the cities. Reducing urban wood consumption is imperative for rural environmental management and can be achieved through more efficient techniques, greater reliance on other fuels, and realistic pricing.

Building-poles used in SSZ countries for traditional construction jobs are not fully termite-proof, especially poles cut from exotic, fast-growing tree varieties. Chemical treatment of building-poles would increase their useful life, reduce consumption and thereby contribute to maintaining the natural forest cover. For this purpose, creosote, one of the byproducts of the carbonization process, could easily be collected from earthen kilns of the type used in the Casamance region for the production of charcoal.

Pricing of fuelwood and charcoal in all SSZ countries is determined primarily by the market. Apart from sporadic but ineffective urban retail price controls, the only public intervention is at the level of fees for cutting. The manipulation of these fees would have direct repercussions on retail prices. While nothing is yet known about demand elasticity or about cross-elasticities, a sustained increase in cutting and transport fees would necessarily promote some economies in the use of fuelwood and, possibly, the substitution of other fuels. Pricing of the other fuels, except for the crop and animal residues, is regulated either directly or by taxation. Since this regulation is effective, there is scope for adjusting prices of substitutes, notably by holding down the kerosene or gas prices or even cross-subsidizing them.

The natural forest cover, the most vulnerable part of the ecosystem, is not just vulnerable; it is already being severely overexploited.

Implications for action

For governments. The priority areas for action by governments are those that, in combination, set the incentive framework for the day-to-day decisions of millions of decision-makers:

· land law and practice, including the forestry code, should be examined to identify and act upon changes required to increase the incentives for sustainable resource management. This examination would be best done by a multidisciplinary task force reporting to the central authority;

· regulations and laws concerning social organization should be examined to identify and act upon changes required to reduce the barriers to the setting up or recognition of genuine grass-roots organizations;

· population control measures should be initiated;

· in a land-use planning framework, settlement policies should be reexamined, with a view to the promotion and support of sustainable spontaneous settlement instead of organized colonization;

· performance in existing irrigated perimeters has to be improved; the enormous potential for increasing carrying capacities via irrigation cannot begin to be tapped through new perimeters until existing perimeters are made more sustainably productive;

· price incentives have to be moved even further in the direction of encouraging more intensive production techniques, and the market displacement effects of food aid have to be even further reduced. There is an overwhelming case for a dramatic increase in permit fees for cutting fuelwood, but there is no case for intervention in retail prices or in marketing. There is a good case for cross-subsidizing the most likely substitutes for fuelwood - namely kerosene and gas - from revenue raised on other petroleum products.

For financiers. For financiers too, a considerable array of actions is foreseeable, but much will depend on those selected as priorities by governments. For each of these, there are corresponding actions that financiers could take, ranging from technical assistance (land law, social organization) to pilot projects (population) to full-scale projects or sectoral adjustment (irrigation, price changes). In some areas, however, the actions that financiers might take are not entirely clear, a notable example being that of settlement. In this area, it is not clear how spontaneous settlement might be assisted beyond putting into place readily enforceable land-use regulations that offer land rights in exe, change for management responsibilities. Given this uncertainty, a, review of settlement activities elsewhere in the world would be a useful contribution to clarifying the options.

DRY STREAM-BED IN SENEGAL a difficult adjustment to drought

For forestry research. Conventional approaches, such as the usual provenance-testing or the use of cuttings for vegetative propagation, are still useful, but the need cannot be stressed too strongly for innovative technologies that will lead to increased biomass production and improved tolerance of trees to environmental constraints. Two approaches already exist that can contribute to the improvement of the plant material and to the establishment of trees in the harsh Sahelian or Sudanian conditions through better use of available moisture and nutrients: the first is based on the use of plant tissue cultures, the second on the manipulation of symbiotic root micro-organisms.

Special attention should be given at the outset to the choice of tree species able to withstand the major climatic and edaphic stresses (drought, fire, nutrient deficiencies).

The next step would be to undertake provenance-testing or surveys aiming at identifying individual specimens (including trees) presenting the greatest adaptability and the most desirable characteristics.

The third step would be to mass-produce clones of the chosen individuals. When using vegetative propagation techniques, all regenerated plants (clones) are, in theory, exact duplicates of the original genotype. There are two main techniques: one is based on the use of rooted cuttings, and the other on the use of tissue cultures. A number of trees are propagated from rooted cuttings (examples are Eucalyptus in the Congo and Brazil and Casuarina funghuhniana in India and Thailand). This sample method should be applied wherever possible, because of its low cost.

Plant tissue culture methods can be applied in a number of other promising areas, such as disease control (meristem tip cultures to remove viruses from infected plants), the long-term storage of germ-plasm and germ-plasm exchange, wide hybridization (for example, in vitro pollination and fertilization, and the fusion of somatic cells or protoplasts), the production of haploid and homozygous breeding lines, and variant selection (for resistance to drought, salinity, etc.).

It is now well established that symbiotic root micro-organisms (Rhizobium, Frankia and mycorrhizal fungi) can effectively contribute to tree productivity in marginal climatic and edaphic conditions. Since significant advances have been made recently in the manipulation of these microorganisms, it is now possible to contemplate their use in the field.

Given the magnitude of the problem, it would be difficult to develop such an ambitious research programme through the existing scattered and often underequipped research centres. A real need therefore exists for a permanently staffed unit in an international or regional centre focusing on Sudanian and Sahelian zone tree and shrub species. Located in the SSZ region, this unit would be the core of a network consisting on the one hand of African forestry centres and projects, and on the other of laboratories in industrialized countries wishing to participate in the improvement of the SSZ forest.

The main objectives of this forestry unit would be the following:

· to identify the local and exotic tree species with the highest potential for wood and fodder production under SSZ conditions;

· to develop the biotechnologies required for improving the behaviour and growth of selected species, these technologies being used in plant tissue culture or in the manipulation of the root symbiotic micro-organisms;

· to study the pathology (especially such root pathogens as nematodes) and some basic problems related to the physiology of selected trees (e.g.. flower biology, resistance to drought, and plant nutrition).

Within the SSZ heartland, no significant change in carrying capacities is possible without a technological breakthrough. Locally, however, the desertification threat may be arrested by selecting appropriate anti-desertification actions and working with communities that are interested and empowered to use their land in a sustained-yield manner. Reducing the continued rapid growth of population is crucial, and current population pressures in the heartland need to be alleviated by further encouraging the existing spontaneous movement of people to the underpopulated, high-potential Sudano-Guinean zone.


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