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Dry forest silviculture in the Sudano-Sahelian region: Burkina Faso's experience

M. Soto Flandez

This article reviews the role of deforestation in accelerating desertification over the past ten years in the remaining wooded areas of the Sudano-Sahelian zone. To avoid both an energy crisis and the prospect of an ecological catastrophe, the article proposes a silvicultural system which proved successful in an FAO/government project in Burkina Faso.

Manuel Soto Flandez is an international forest management consultant associated with the Southern University of Chile. He was Chief Technical Advisor to an FAO-assisted fuelwood project in Ouagadougou, Burkina Faso (FAO/BKF/89/0 11).

Healthy dry tropical forest in Burkina Faso

The Sahel in West and Central Africa was hit by an unusually severe series of droughts 20 years ago. The scale of this tragedy, which claimed the lives of thousands of people and millions of animals, drew universal attention to the effects of desertification, the process whereby natural resources are degraded as a result of human activities (Grainger, 1985).

Ever since, both the countries involved and international economic assistance agencies have expended considerable effort in an attempt to halt and even reverse this trend: first, by reforesting with exotic species, building dams, sinking wells and developing agroforestry, into which some hundreds of millions of dollars have been channelled in the past two decades. Sadly, however, the problem is still far from being resolved.

Technically speaking, results have been fairly lukewarm. Efforts to reforest with exotic species such as Eucalyptus spp., Gmelina arborea, Cassia siamea and Azadirachta indica at an average cost of more than US$ I 000 per hectare have not brought the desired outcome. Trees selected without earlier trials have been planted on inappropriate sites where they have rarely shown an annual volume increase of more than 2 m³ per hectare compared with the anticipated 10 to 15 m³ per hectare. Another factor has been the rejection of such activities by rural people who, having seen radical changes in the use of the land, have failed to reap any substantial benefits in exchange. Most of the dams were not accompanied by the agricultural development infrastructure and farmer training that would have made them useful, while some are now simply reservoirs in the process of being choked by erosion from the surrounding denuded land. Agroforestry is merely marking time within the confines of pilot areas for as long as project financing lasts and the methods proposed are not being widely diffused anywhere in the region. The agricultural techniques proposed by the expensive extension services have not even proved able to slow the loss of soil fertility or the virtually irreversible degradation of the area's land and plant resources (Pier), 1989).

The result is a process of desertification that has been aggravated in recent decades by explosive annual population growth rates of about 3 percent in the subregion and that is taking place in a context of structural economic adjustment and deteriorating terms of trade. Faced with rising input costs and falling market prices, the farmer's only choice is to migrate to the city or to move into areas where there are still trees. Those who remain are forced into shifting cultivation and subsistence farming, given that there is absolutely no way they can afford the fertilizer that would keep the land fertile (FAO, 1994).

Deforestation, the end result, is irreversibly changing the face of the entire region and consequently forcing a search for alternatives in forestry; namely silviculture and local species management.

The Sudano-Sahelian region

The Sudano-Sahelian region considered here covers 16 countries: Benin, Burkina Faso, Cameroon, the Central African Republic, Chad, Côte d'Ivoire, the Gambia, Ghana, Guinea, Guinea-Bissau, Mali, the Niger, Nigeria, Senegal, the Sudan and Togo. The combined population of these countries, estimated to be 116 million in 1970, is expected to reach 294 million by the year 2000.

The geographic Sahel region extends from the Sahara to the tropical humid zone and comprises three agroclimatic zones: the Sahelian zone which includes a pastoral region and has a rainfall of less than 200 mm: a precarious agricultural region, with a rainfall of 400 mm and a dry savannah type of natural vegetation; and a zone that roughly covers the Sudano-Sahelian, Sudanese and Sudano-Guinean region, with a shrub and tree savannah vegetation and a single rainy season which brings between 500 and 1 200 mm of rainfall per year.

The remaining wooded areas of the Sudano-Sahelian region act mainly as a scantly populated land reserve and thus as a safety valve for the rising social and economic tensions provoked by declining terms of trade, the saturation of land resources and soil exhaustion in other areas. This trend in the region is resulting in fast-shrinking forest formations, with cleared areas nibbling systematically into the fabric of the forest.

The second use of the remaining wooded areas is to provide forest products, including "dead" wood left on the ground after the land has been cleared or swept by brush fires. Fuelwood consumption is of signal importance in an area where the supply of oil and electrical power is unreliable, nonexistent or unaffordable where available. On average, fuelwood consumption accounts for 90 percent of the total energy consumption figure. According to the Organisation for Economic Cooperation and Development (OECD, 1988), there are no economic prospects for the substitution of fuelwood by imported fuels within the next few decades.

The third use of the forest resource is for livestock production, mainly under transhumant and extensive systems which result in overgrazing, the lopping of trees for fodder, the destruction of natural regeneration and the ravages of brush fires deliberately set to favour the regrowth of new, healthy grass.

Looking for strategies

With growing national and international awareness, there have been cries of alarm concerning the clear risk of an energy crisis accompanied by an ecological catastrophe (World Bank, 1993). The response of governments, backed by international economic assistance, has been to launch new projects to assess and tap the true potential of local tree species. Since the 1980s, therefore, almost every country in the region has been the scene of silvicultural and forest management projects.

The result of controlled burning in dry tropical forest in Burkina Faso

However, the history of subhumid to arid forest silviculture and management in the Sudano-Sahelian zone dates all the way back to the 1940s, when it was mainly practiced in a summary fashion for the production of fuelwood for trains (in Senegal, the former French Sudan and the present-day Sudan, etc.) and to supply certain products, e.g. management of the Baudia forest in Senegal for timber and fuelwood. More recently, following on the heels of negative experiences in plantations, a series of projects and national initiatives have promoted better natural regeneration through low-tillage cultivation, wildfire protection and the enrichment of forest belts along the southern fringe of the region. From the mid- 1970s, a number of management projects with major silvicultural components sprang up in response to the need to complement at least (if not replace) plantation forestry with the management of natural forests. These experiences, which included failures, problems and a few successes, confirmed the need to: manage the natural forests, enlist people's participation and involvement in land management and foster multi-use production forestry. Following this line, FAO launched a number of experiments in the region (Burkina Faso, Mali, the Niger and Senegal).

The results of a UNDP-financed, FAO-executed project (Natural forests management and fuelwood supply project BKF/ 89/011), undertaken in Burkina Faso from 1987 to 1993, could point the way to successful silvicultural development in the Sahel. The project area lay south of Ouagadougou between lat. 12°05'N and 11°35' N and long. 2°25'W and 0°55' W in the north Sudanese climatic zone which has an annual rainfall of 700 to 900 mm.

An appropriate silvicultural approach

The main objective of the project was to help supply Ouagadougou with fuelwood by way of an approach that enlisted the participation of the rural population. Basically, the task of the project was to identify a silvicultural approach that could at once ensure reforestation, be applied by the local people themselves and be self-financing through the income obtained from fuelwood sales. The methods and techniques described below summarize the experience of six years of silvicultural work in the field.

The system adopted by the project was that of the coppice-with-standards (or shelterwood) technique. The treatments associated with this regime, as developed for Sudano-Sahelian conditions, were: a progression of cuts every ten years, enrichment by direct sowing with local species and early prescribed burning to control grass growth and prevent late-season wildfires. Accompanied by progressive cuts, the coppice-with-standards regime was specifically chosen to ensure the establishment of a new stand sheltered by the remaining portion of the old stand.

The application of the silvicultural regime consisted of a first partial cut in the first year and a second after ten years for a 20 year rotation. In the first cut, half of the standing volume is harvested, thereby favouring the development of a new stand while conserving tree cover to facilitate both vegetative and sexual regeneration. The second cut is done only after ten years when the new stand is completely established (FAO, 1992a).

Regeneration by direct sowing

Experience shows that, even if most northern Sudanese species coppice. successive cuttings may well weaken the stand. Vegetative regeneration therefore needs to be paired with sexual regeneration to replace the dead stumps. This is done through site improvement to facilitate regeneration through natural or artificial reseeding.

Natural regeneration has a number of inherent problems: most species fruit in the dry season, making the germination of the seeds which fall on dry ground highly problematic. Grass cover also often prevents the seeds from reaching the soil while brush fires destroy most of the successfully established seedlings (Catinot, 1984). Conventional reforestation through the planting of seedlings is not a viable option either, as the work in the nursery as well as the transport of materials and seedlings are far too expensive for the level of income that fuelwood production can provide. The project therefore developed an enrichment technique using direct sowing. The principal advantages of this method are its low cost and its easy and immediate mastery by farmers - there being, in fact, no fundamental difference between this technique and that of growing agricultural crops. The main drawback is the lack of available information on the ecological requirements and biology of local species. It is important to remember that the forest formations of the Sudano-Sahelian region are fairly diverse in floral composition, with some 40 woody species in the north Sudanese Savannah zone and more than 80 in the Guinean zone. Apart from the botanical descriptions, there are no silvicultural data on these species; the need for protection against fire and trampling by livestock during the first 24 month of life is, however, a known requirement.

Collecting local seed for regeneration by direct sowing

The lack of information and experience concerning the use of local species was partially bridged by a research support programme covering seed harvesting, treatment, germination and behavioural trials as well as direct sowing methods. These experiments produced: i) the identification of a group of promising species; ii) mastery of the cycle of seed harvesting, processing and germination with a final success rate of at least 50 percent or more; and iii) the selection of appropriate species for three different ecological situations. For thoroughly cleared savannah sites exposed to strong sunlight and colonized by a dense cover of grasses subject to periodic burning, the following thick-rhytidome, big-budded species with relatively small leaf areas were identified: Detarium macrocarpum, Piliostigma sp., Terminalia avicennioides, T. rnacroptera and Butyrospermum parkii.

The following species were selected for logged parcels where 50 percent of volume had been left standing, thereby reducing the amount of sunlight reaching the ground and consequently the development of the understorey grass layer: Afzelia africana, Tamarindus indica, Anogeissus leiocarpa, Burkea africana and Prosopis africana.

The species selected for riparian areas were: Khaya senegalensis, Daniellia oliveri, Isoberlinia doka, Pterocarpus erinaceus and Mitragyna inermis. Both acacias and Dichrostachys glomerata with Ziziphus mauritiana were incorporated on all three types of site to create thickets that would impede the passage of livestock and serve as firebreaks.

All the exploited areas were seeded at a density of 625 planting-holes per hectare. The number of seeds per hole was calculated in accordance with the germination rates established in previous trials. The seeds were collected by local farmers in the forests scheduled for enrichment and were then purchased, treated and stored by the project. The average cost of direct seeding in 1993 was CFAF 2076 per hectare (US$8), broken down as follows: 9 percent for seed purchase and storage; 55 percent for labour and supervision; 13 percent for the prevention of unauthorized and unregulated brush burning; and 23 percent for technical assistance and administration.

Early prescribed burning

The silvicultural system established by the project included the use of early prescribed burning to reduce the danger of dry-season wild fires. It is recognized that fires are deliberately set by people every year as a brush-clearing technique, to destroy stubble, to promote clean and healthy pastures and to force the regrowth of perennial grasses. Therefore, until alternative solutions are provided by the intensification and modernization of crop and livestock production, fire will continue to be a factor in forest development. The project therefore concentrated on identifying the impact of fire on trees and on developing a technique for early prescribed burning.

Storage of locally collected seed

Survey data in the project area indicated that more than 80 percent of the trees surveyed bore cambium wounds at the base of the trunk. These wounds, enlarged year by year, are what cause the main tree-trunk to break and give rise to a new cycle of natural pollarding, which is why the savannah stands are not very old. "Normal" cycles marked by moderate fire pressure are rarely of more than a 30-year duration. Rotations can become very short, however, if regular late-season fires find deadwood and grass to feed on: in this case the rootstock may well be killed.

For the early prescribed burning, 4 m forest strips were cleared perpendicular to the direction of the dominant dry-season winds. Spacing of the strips, dictated by establishment costs, could not exceed 500 m. The strips were used for starting early burning.

Exploited and enriched forest areas were protected by an 8 m perimeter strip that was also used as a service road and fire-break for two consecutive dry seasons. The prescribed burning period was undertaken during the second or third week after the end of the rainy season, depending on when the moisture content of the understorey grass reached an appropriate level. The fires were lit upwind to form an initial protective ring, and then downwind to accelerate burning without allowing the fire to get out of hand.


The regression of the forest in the dry regions of Africa is due to the fact that modern agriculture, i.e. intensive as opposed to extensive, is not being developed at an appropriate pace. The statement applies to the entire Sudano-Sahelian region where forests are giving way to agriculture. Reforestation with exotic species has frequently failed. Together, the gathering of fuelwood supplies and the rupture of ecological equilibria could well trigger new emergencies in the region.

Forest promotion and development require farmers' participation. Governments in the region and international donors increasingly acknowledge that setting aside an area for forest production involving farmers' participation in management can be a way of controlling the damages of deforestation.

Appropriate silviculture for the region

Project progress at the end of the second phase in 1993 added up to 100 000 ha of managed natural forest, with a sustained annual production of 60 000 m³ of fuelwood and regeneration by direct sowing on 12 000 ha, of which 45 percent by reforestation and 55 percent by enrichment of exploited parcels. Forest productivity, measured under conditions equivalent to those of the project, is estimated to be 3 m³ per hectare per year (FAO, 1992b). This experiment in forest management, which was well received by the rural population, gave rise to the organization of 56 rural associations with a membership of 5 000 farmers belonging to three forest production cooperative unions. The success of the model attracted the interest of the Burkina Faso Government and donors, with UNDP deciding to finance a third phase for 1994-1998. The World Bank has supported a similar project in the Bobo-Dioulasso region, and the European Community has financed the development of an additional 50 000 ha in the same area as the UNDP project (FAO, 1993).

The experience in Burkina Faso has made a good start towards the development of appropriate silvicultural practices for the region. Its results hold promising prospects for natural forest rehabilitation and conservation and have helped to revitalize research and training in as well as implementation of the appropriate silviculture for this region.


Catinot, R. 1984. En Afrique francophone l'avenir forestier se jouera dans le cadre du monde rural, Paris, CTFT.

FAO. 1992a. Aménagement des forêts naturelles et semis direct. Project FAO/BKF/89/011. Ouagadougou.

FAO. 1992b. Evolution d'un taillis deformation naturelle soudano-sahélienne. Project FAO/ BKF/89/01 1. Ouagadougou.

FAO. 1993. Aménagement des forêts au Burkina Faso. Terminal report. Project FAO/ BKF/89/011. Rome.

FAO. 1994. Etude sur la gestion forestière du Sénégal. Project FAO/TCP/SEN/4452. Dakar.

Grainger, A. 1985. Desertification. London, Earthscan.

OECD. 1988. Le Sahel face aux futurs. Dépendance croissante ou transformation structurelle. Etude prospective des pays sahéliens 1983-2010. Paris.

Pieri, Ch. 1989. Fertilité des terres de savane. Bilan de trente ans de recherche et de développement agricole au sud du Sahara. Paris, Ministry of Cooperation and Development CIRAD-IRAT.

World Bank. 1993. Sénégal. Rapport d'actualisation economique. Sahel Department, Washington, DC.

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