2.1.3 Tendances dans l'exploitation forestière
Le désir du Sénégal de limiter le déficit de sa balance commerciale, joint aux difficultés qui naîtront de l'approvisionnement en grumes provenant de la Côte-d'Ivoire dont les réserves s'épuisent rapidement, conduit à envisager un certain essor de l'exploitation de bois d'oeuvre en Casamance. La scierie pilote montée par la FAO à Ziguinchor devrait susciter d'autres installations dans la région. De ce fait, on peut estimer probable l'exploitation d'environ 35 000 m3 de grumes en 1985. On retiendra le chiffre moyen de 30 000 m3 pour la période 1981–85.
L'accroissement de la population entraînera une augmentation de l'exploitation de bois de chauffage et de bois de service. En ce qui concerne le bois de feu l'évolution des besoins est résumée dans le tableau suivant:
Evolution des besoins en bois de feu 1
|Population||Besoins en bois de feu||Population||Besoins en bois de feu|
|Ouest||2 450||1 480||4 660||2 500|
|Sine Saloum||1 140||680||1 690||1 000|
|Total||5 730||3 440||9 580||5 350|
1 Population en milliers d'habitants et besoins en bois de feu en milliers de m3.
Pour faire face à cette demande et enrayer (ou tout au moins limiter la surexploitation des forêts), il sera nécessaire de réaliser des reboisements importants et surtout des actions d'aménagement et protection des formations naturelles sahéliennes, soudano-sahéliennes et soudano-guinéennes.
Enfin, un déplacement vers le Sénégal oriental de l'exploitation de bois de feu sera absolument nécessaire pour subvenir aux besoins des régions de l'ouest, en particulier des centres urbains.
2.1.4 Surfaces et volumes sur pied à la fin de 1985
Les considérations précêdentes conduisent aux tableaux ci-après:
Surfaces estimées de végétation ligneuse naturelle à la fin de 1985
(en milliers d'ha)
|1 665||7 650||1 265||8 915||10 580||1 875||1 265|
Volumes sur pied estimés à la fin de 1985
(en millions de m3)
Les estimations totales des volumes bruts (VOB) et “actuellement commercialisables” (VAC) des formations ouvertes productives (NHc/NHO1) ont été déterminées en tenant compte de la réduction par défrichement des surfaces correspondantes et de l'impact de l'exploitation forestière pendant la période 1981–85. Défrichement et exploitation ne devraient pas affecter significativement les forêts denses (NHCf).
Onze projets de reboisement en cours ou en période de démarrage peuvent être répertoriés (16) (25):
|Reboisements irrigués fleuve Sénégal||FAC (France)||protection/production||1 200|
et crédits équipement
|production de fourrage (gommiers et autres acacias)||25/an|
|Reboisement et aménagement sylvo-pastoral en zone nord||Allemagne et crédits équipement||protection/régénération des pâturages||600/an|
|Reboisement de fixation des dunes du Goudrolai||Canada||fixation des dunes||1981: 140 à partir de 1982: 150/an|
|Fixation des dunes et protection des sols le long de la route Lompoul-Kebemer||fixation des dunes|
|Fixation des dunes du Cap Vert||fixation des dunes||50/an|
|Reboisement forêt de Bandia||Etats-Unis||6000 (en deux tranches de 5 ans)|
|Reboisement forêts du centre-est||FAC|
|plantations bois de feu irriguées/plantations rurales et communautaires (eucalyptus)||1981: 400|
|Plantations d'anacardier dans le Sine Saloum||Allemagne||5000 en 4 ans (80–83)|
|Projet Lagbar (Union internationale pour la protection de l'enfance)||UIPE||création aires d'ombrages (gommier)||100|
|Reboisement axe Ndiousome-Ndangane||AFRICARE||100|
|Petit reboisement à Loul Sessinre|
Si l'on fait la somme des programmes prévus par ces onze projets, on aboutit au chiffre de 16 000 hectares pour la période 1981–85, dont 6 000 ha d'eucalyptus (à croissance relativement rapide), 5 000 ha d'anacardier, 1 200 ha de filao, environ 200 ha de gommiers et le reste en espèces diverses: neem, Acacia spp., Prosopis, etc. Le Secrétariat d'Etat aux forêts, soucieux de la réalisation effective de ces programmes, a préparé un décret organisant leur gestion et contrôle techniques. Il semble, en effet, qu'un des principaux facteurs d'échec ait été dans le passé la lenteur de la mise en place des crédits et leur mauvaise gestion. On peut espérer dans ces conditions, et compte-tenu de l'attention particulière que les problèmes forestiers reçoivent actuellement au Sénégal, que ces programmes seront réussis à 80 %, soit une surface totale plantée, de 1981 à 1985, de 13 000 ha environ à laquelle on peut ajouter 1 000 ha réalisés durant cette période par les villageois avec l'aide du Service forestier.
Il convient enfin d'ajouter qu'il ne semble pas vraisemblable actuellement que les plantations industrielles de teck et de Gmelina doivent être reprises à grande échelle d'ici 1985.
Les considérations précédentes conduisent aux tableaux suivants:
Surfaces estimées des plantations industrielles réalisées à la fin de 1985
(en milliers d'ha)
|PHL 1||Tectona grandis||0,4||0,5||0,4||0,6||1,9|
|PHH 1||Gmelina arborea||0,8||0,3||0,3||0,2||1,6|
|P..1 = PH.1||Total plantations industrielles||1,2||0,8||0,7||0,8||3,5|
Surfaces estimées des plantations non-industrielles réalisées à la fin de 1985
(en milliers d'ha)
|Classe d'âge||0–5||6–10||11–15||16–20||21–30||31–40||> 40|
|PHL 2||Acacia spp.,|
(fixation des dunes)
|Acacia senegal, Acacia spp.,|
|Sous-total PHL 2||9,0||6,6||1,8||0,4||17,8|
|PHH 2||Eucalyptus spp.||5,0||0,2||5,2|
|P..2 = PH.2||Total plantations non-industrielles||14,0||6,8||1,8||0,4||23,0|
Surfaces estimées des plantations réalisées à la fin de 1985
(en milliers d'ha)
|PHL||Espèces feuillues non à croissance rapide||9,0||7,0||2,3||0,4||0,6||0,4||19,7|
|PHH||Espèces feuillues à croissance rapide||5,0||1,0||0,3||0,3||0,2||6,8|
|P = PH||Total toutes plantations||14,0||8,0||2,6||0,7||0,8||0,4||26,5|
Aubréville, A. 1938 “La forêt coloniale: les forêts de l'Afrique Occidentale Française” - Paris
Trochain, J. 1940 “Contribution à l'étude de la végétation au Sénégal” - Mémoires de l'IFAN - Paris
Aubréville, A. 1949 “Climats, forêts et désertification de l'Afrique tropicale” - Paris
Aubréville, A. 1950 “Flore forestière soudano-guinéenne - A.O.F. - Cameroun - A.E.F.” - Paris
Fowry, P. 1953 “Politique forestière au Sénégal” - in Bois et Forêts des Tropiques no 30 - Nogent-sur-Marne (France)
Giffard, P.L. 1958 “Les plantations d'alignement en zone sahélo-soudanienne” - Direction des Eaux et Forêts - Dakar
Deschamps, H. 1964 “Le Sénégal et la Gambie” - Presses Universitaires de France - Paris
Adam, J.G. et al 1965 “Connaissance du Sénégal: climat, sol et végétation” - Etudes sénégalaises no 9 - Dakar
Giffard, P.L. 1969 “Les peuplements d'anacardier au Sénégal” - Centre Technique Forestier Tropical - Dakar
Giffard, P.L. 1971 “Evolution des peuplements forestiers au Sénégal” - Centre Technique Forestier Tropical - Dakar
Giffard, P.L. 1974 “L'arbre dans le paysage sénégalais” - Centre Technique Forestier Tropical - Nogent-sur-Marne (France)
Giffard, P.L. 1974 “Les essences de reboisement au Sénégal” - Centre Technique Forestier Tropical - Dakar
Poupon, H. et Bille, J.C. 1974 “Recherches écologiques sur une savane sahélienne du Ferlo septentrional, Sénégal - Influences de la sécheresse sur la strate ligneuse” - in La Terre et la Vie - tome 28 no 1 - Paris
Conseil interministériel 1975 “Conseil interministériel sur les eaux, forêts et chasses du 16 Juin 1975” - Dakar
FAO 1975 “Mise en valeur de la Basse et Moyenne Casamance - Inventaire forestier”- Rapport préparé par le Centre Technique Forestier Tropical- Projet DP/SEN/71/522 - 1/FO - Nogent-sur-Marne (France)
Direction des Eaux, Forêts et Chasses 1976 “La situation forestière au Sénégal”- Rapport présenté à la Consultation sur le rôle de la forêt dans un programme de réhabilitation du Sahel" (Dakar, 26 Avril – 1er Mai 1976) - Dakar
FAO 1976 “Rapport de mission d'évaluation de projet forestier au Sénégal et identification de projet forestier en Mauritanie” - par G. Guigonis - TF/SEN/16(U.S.A.) - Land Resources Management - Forestry and Forest Economics Consultancy - Rome
SONED/SODETEG 1977 “Etude d'un plan de développement régional intégré du Sénégal oriental - Tome 3: les forêts” - Ministère de Plan et de la Coopération- Dakar
Direction des Eaux, Forêts et Chasses 1978 “Rapport annuel - 1978 - Inspection régionale du Cap Vert” - Dakar
Direction des Eaux, Forêts et Chasses 1978 “Rapport annuel - 1978 - Inspection régionale du Fleuve” - Dakar
Direction des Eaux, Forêts et Chasses 1978 “La gommeraie au Sénégal et les plantations du Centre de Mbidi” - Dakar
FAO 1978 “Rapport final (sylviculture)”- par R. Langley - SEN/71/522 - Document de travail - Rome
Direction des Eaux, Forêts et Chasses 1979 “Rapport annuel - 1979 - Inspection régionale de Diourbel” - Dakar
Direction des Eaux, Forêts et Chasses 1979 “Rapport annuel - 1979 - Inspection régionale de Louga” - Dakar
Direction des Eaux, Forêts et Chasses 1979 “Rapport annuel - 1979 - Inspection régionale du Sénégal oriental” - Dakar
Sene, E.H. 1980 “Analyse des projets forestiers en cours” - Direction des Eaux, Forêts et Chasses - Dakar
The Republic of Sierra Leone lies between latitudes 7° and 10'N and longitudes 10° and 14°W on the west coast of Africa, covering an area of 73 326 km2. The country is divided into three provinces (Southern, Eastern, Northern) and the Western Area, the peninsula on which the capital, Freetown, is situated.
Sierra Leone can be divided into four main physiographic zones. The Gabro massif in the Western Area rises to 1 000 m altitude. The three other main regions running roughly parallel to the coast from northwest to southeast are:
more inland an upland plateau of up to 600 m altitude with mountain ranges culminating at 1 950 m in the Loma Mountains.
The climate is tropical, showing distinct dry and rainy seasons. The latter extend from May to November, with a precipitation ranging from 2 000 mm in the north to more than 5 000 mm along the coast. The main temperature varies between 22°C at night and 35°C during the day. Owing to the high rainfall, the soils of Sierra Leone are endangered by erosion, especially on the slopes where the vegetation has been burned. All over the country, hilltops, which lost their arable topsoil after shifting cultivation, are now covered solely by grass or spares bushes.
Total population is estimated at about 3.4 million inhabitants in 1980, increasing at an annual rate of 2.6%, with a particularly steep increase in the urban regions (e.g. approximately 7% annually in Freetown) (13). With an average population density of 46 persons per km2, Sierra Leone is one of the most densely populated countries of Africa. 65% of its economically active population are working in the agricultural sector, the main cash crops being cocoa, coffee, oil palm, raffia palm and ginger (13).
1. Present situation
1.1 Natural woody vegetation
The vegetation of Sierra Leone is almost everywhere the result of the heavy pressure exerted by a very dense population. Only few, very limited areas of the country carry a climax vegetation
1.1.1 Description of the vegetation types
Three major vegetation zones occur from the southwest coast to the interior, namely coastal mangrove, forest and savanna. The forest and savanna zones have a less dense drainage pattern than the mangrove zone and tend to have fairly flat and narrow inland valleys which are seasonally flooded. The following description is based on (10) and uses as a frame the broad categories of this study.
Closed broadleaved forests (NHC)
- Closed forests on dry lands are either moist evergreen or semi-deciduous forests and are mostly located in forest reserves on hill slopes (Gola, Kambui, Nimini, Dodo Hills, Freetown Peninsula, Tama-Tonkoli, Kasewe, Loma and Tingi Hills). They have a closed canopy and trees over 30 m high and are generally nature secondary forests, with a large number of species and a very uneven distribution. The moist semi-deciduous forests are found on the Loma Mountains and the Tingi Hills forest reserves, and also in Kasewe, Tonkoli, Golama North and Golama South forest reserves and in extension 1 of Gola East forest reserve. The former ones gradually change into submontane gallery forests reaching 1 700 m altitude. In such situations epiphytes are abundant. Patches of degraded forest occur, where large trees have been removed for timber or with an undergrowth of cocoa or coffee, often on the fringes of cultivated areas or in the more accessible locations of the forest areas. Typical moist evergreen forest trees are: Lophira alata, Heritiera utilis, Klainedoxa gabonensis, Uapaoa guineensis, Oldfieldia africana, Erythrophleum ivoransis, Brachystegia leonensis and Piptadeniastrum africanum. Common semi-deciduous forest trees are Daniallia thurifera, Terminalia ivorensis, T. superba, Parkia bicolor and Anthonotha flagrans which are associated with evergreen trees such as: Parinari excelsa, Bridelia grandis, Treculia africana and Pycnanthus angolenais. Logging has been going on for several decades and there is practically no virgin forest left.
- Young secondary forests deriving from former clearing by agriculture of the forests on dry land are mainly found in the southeastern part of the country on hill slopes. They have a closed canopy and trees range in height from 10 to 30 m. The majority of the tree species are fast-growing and more or less even-aged with distinctive small crowns. They are replaced by slow-growing typical high forest species as the forest matures. Tree-crop species and a few large forest trees left standing after farming are also common. Secondary forest trees are Musanga cecropioides, Carapa procera, Macaranga barteri, Anthocleista nobilis, Bridelia micrantha, Myrianthus arboreus, Phyllanthus discoideus and Sterculia tragacantha. These species are confined to the lowest tree stratum. They are overtopped by typical mature forest species such as Afzelia africana, Albizia zygia, Uapaca guineensis, Daniellia thurifera, Terminalia superba, Parkia bicolor and Entandrophragma utile. Associated tree-crop species are Wangifera indica, Elaeis guineensis and Cola nitida.
Secondary forests are a locally exploited source of timber and firewood. Near villages, they provide a suitable habitat for an undergrowth of cocoa and coffee. A large proportion of this type occurs outside forest reserves and is thus the object of further degradation where population pressure is high.
- Fringing awamp forests are mainly present in the northern part of the coastal area and situated along valley bottoms, shallow drainage ways and lake margins, e.g. lakes Magbesi and Makpe. Their (usually) closed canopy contains trees up to 30 m high. Stilt roots and buttresses are common. These forests are subject to seasonal flooding, while in the dry season the ground is muddy. On the edge of large shallow lakes they become more open and the trees are often lower. Typical species are Pterocarpus santalinoides, Newtonia elliotii, Myrianthus arboreus, Plagiosiphon emarginatus, Uapaca heudelotii, Napoleana vogelii, Cynometra vogelii and Placodiscus riparius, with trunks covered by bushy pneumatophores at the flood level. Some paddy rice cultivation occurs. These swamp forests are cleared for agriculture to a limited extent only.
- The Raphia sp. occurs in valley bottoms within both the moist forest and the savanna zones. The canopy is usually closed and the trees measure up to 20 m. In the freshwater environment of the swamp a process of colluvial sedimentation prevails under conditions of seasonal flooding. Raphia palms (R. vinifera) are dominant and often constitute a regrowth stage, together with climbing rattan palms of Ancistrophyllum secundiflorum, Eremospatha nookeri and Calamus decratus. Most usual swamp tree species are Nauclea diderrichii and Mitragyna stipulosa. The undergrowth consists of ferns and other moncotyledons. Some Raphia swamp forests are cleared by man for cultivation in the dry season.
- Mangrove forests are found in the coastal area, usually on tidal flats at the mouth of rivers. Stilted shrubs or trees are frequent. Height may be up to 20 m. Along creeks, the trees are larger and the forest is dense resulting in a “gallery forest effect”. The mud flats between creeks have a low mangrove cover usually leas dense. The main tree species are: Rhizophora racemosa, R. mangle and R. harrisonii. The first one is a pioneer species at the edge of the water while the other two are dominant upstream at the tidal limits, where also Avicennia nitida with pneumatophores, Conocarpus erectus and Laguncularia racemosa can be found. On the fringe of the mangrove, grasses occur together with ferns and halophytes. The mangrove cover is now mainly made up of low regrowth and few trees of any size. This is very characteristic in the area around Freetown, which has apparently been cleared for poles and fuelwood in the past. Paddy rice cultivation is present in other zones.
- Forest regrowth occupies part of the country which was covered formerly with closed high forest. In the western part of Sierra Leone it extends south of about 9°30'N and towards the eastern border south of about 9°05'N. Various stages of regrowth from abandoned farm bush to young secondary forest are represented in this vegetation type. When left standing for about 8 to 10 years, it will develop into secondary forest. In many cases, however, the bush fallow cycle is reduced to a few years and the thicket is burnt before secondary forest stage is reached. Trees are up to 10 m high. The farmbush is generally overgrown by shrubby or suffrutescent weeds. This develops into a thicket with numerous woody climbers. Scattered large forest and tree-crop species were sometimes left standing during the clearing operation. Typical thicket species are Lantana camara, Cissus afzelli, Manniophytum fulvum, Abrus precatorius, Smilax krausiana, Discorea bulbifera, Clematis grandiflora, Adenia lobata and Scleria bovinii. Eventually, pioneer secondary forest trees such as Dichrostachys glomerata, Harungana madagascariensis, Nauclea latifolia, Alchornea cordifolia and Trema guineensis replace the farmbush and thicket. Elaeis guineensis is a common tree-crop.
Open broadleaved forests (NHc/NHO)
- Savanna woodlands occur in the northern part of the plateau region, on hill slopes and on undulating terrain. The crown cover ranges generally between 20 and 50% and between 50 and 80% in only a few small areas. Trees may be as high as 15 m and an undergrowth of tall grasses (3 m) is practically always present. The trees are often gnarled and fire resistant. Many of them have a thick bark and are deciduous in the dry season. After burning, they produce suckers or coppiced shoots. Typical species are Pterocarpus erinaceus, Hymenocardia acida, Daniellia oliveri, Parkia biglobosa, Cussonia barteri, Piliostigma thonningii, Phyllanthus discoideus and Cassia sieberiana. The savanna woodlands are used extensively for grazing after burning. They are also cleared in some areas for mixed cropping, cassava and rice being the most important ones.
- Coastal woodlands are only found on inland beach ridges in the southwestern coastal area. They are characterized by a relatively closed canopy of savanna trees and secondary forest trees not higher than 30 m. The trees are often stunted and have an undergrowth of low thicket and creepers. The sandy soil on which they vegetate is often subject to flooding in the wet season. Limited burning occurs in the dry season. Coastal woodlands contain stunted species such as Cassia mimosoides and Hymenocardia acida, coastal tree savanna species such as Parinari macrophylla and Chrysobalanus elleptious and forest regrowth species such as Anthostema senegalensis. The undergrowth is characterized by various farmbush species of Dissotis, Borreria and Leguminosae as well as Habropetalum dawei and Triphyophyllum pinnatum.
- “Mixed” tree savannas occur in the northern and northeastern drier parts of the country on hill slopes and undulating plains. They consist of grasses up to 3m tall with scattered trees. Their characteristics are similar to those of the savanna woodland, but the crown cover percentage varies between 2 and 20% only.
- Lophira tree savannas are mainly found in the northwestern part of the country on lateritic pans and undulating plains. They are the result of edaphic conditions, namely shallow soils over lateritio layers in combination with grazing and dry season burning. Gnarled and stunted shrubs or trees up to 12 m high are characteristic. After burning they develop bright green suckers or coppiced shoots. Lophira lanceolata is the dominant species, associated with Pterocarpus erinaceus. Ever present tall grasses reach heights of 3 m. This type of tree savanna is exclusively used for grazing. Patches of forest fallow occur locally.
- Coastal tree savanna are found on coastal beach ridges and swales in several areas along the coast but mainly in the south on Bonthe Island and Turner's Peninsula. The excessively drained sands cause drought conditions in the dry season. At the same time, the vegetation is exposed to salty sea winds and occassional fires. Among medium height grasses up to 1.5 m tall, scattered shrubs or trees of maximum 15 m occur with Parinari macrophylla dominating. They are often gnarled and have xeromorphic characteristics. Coppioing is a common feature.
Shrub formations (nH)
- Montane thicket and grassland: this mixed vegetation type occurs between 900 m and 1 900 m altitude on the Loma Mountains and the Tingi Hills in the northeastern part of the country, where the average temperature is the lowest of the whole of Sierra Leone. The slopes and plateaus are subject to annual burning. Typical shrubs are Kotschya ochreata, Dissotis fructicosa, Monechma depauperatum and Droogmansia scaettaiana. They are scattered in a medium (1.3 m) height grass cover, but disappear above 1 700 m. Their height, up to 5 m, varies with altitude. Although these areas have a potential for grazing, they have been abandoned.
1.2.2 Present situation of the woody vegetation
Area estimates given in the following table are mainly based on the “Vegetation and Land Use Map” (10) at 1/500 000 scale. The latter has been elaborated from 1/70 000 infrared colour aerial photographs, mostly dating from end 1975 and beginning 1976. The area estimates have been adjusted in accordance with suggestions made in (14), and actualized for the end of 1980 taking into consideration the deforestation rates and degradation patterns set out in section 2.1
Areas of natural woody vegetation estimated at end 1980
(in thousand ha)
Impact of man on the natural forest has been so widespread in the last centuries, that no virgin forest is left in the country (NHCf1uv = 0).
Although approximately 93 000 ha of forest reserves are said to be under working or management plans (12), the strict definition of ‘intensive management’ as utilized in this study does not allow classification of the former as ‘intensively managed natural forest’ (NHCf1m = 0).
70% of all forest reserves in the closed high forest zone can be considered of commercial value (24). Taking the same percentage for the remaining unreserved dense forests and accepting 10% of the secondary forests being mature enough to be classified as productive, a total of 219 000 ha of productive natural forest (NHCf1uc) is available for further logging.
Unproductive closed forests (NHCf2(i)) include:
For reasons of inaccessibility and poor stocking, the mangrove and fringing swamp forests have also been classified under this group (NHCf2). Forest regrowth and the Raphia swamp forest constitute dense woody vegetation covers strongly degenerated by agricultural activities.
Although (14) mentions only 40 000 ha of accessible productive woodlands (NHc/NHO1) inside the forest estate, roughly 20% of the savanna and coastal woodlands are presumed to have production potentials, the remainder, together with the tree savanna, not holding any commercial value in the sense defined for this study (NHc/NHO2).
Since the agricultural impact in the woodland/savanna zones is much less than in the dense forest region (14), only one quarter of the corresponding vegetation types is estimated to be continuously affected by shifting cultivation or/and grazing practices (NHc/NHOa).
The surface of shrub vegetation has been estimated at 75% of the area of the “montane grassland zone” (13).
Apart from the forest estate in the Western Area, which largely has protection functions (e.g. Peninsula Hills), all forest land is communally owned. The traditional land use rights are determined by the tribal low of the West African ethnic groups. Thus the members of one tribe, which lays claim on a particular area, forested or not, also possess the rights of land use. These rights mainly concern hunting, collection of plant and animal products, the utilization of fuelwood and building timber, and shifting cultivation as part of agricultural utilization and grazing rights (13). The principle under which all land belongs to the population also provided the foundation for the Forestry Act of 1912 which dictates that before a forest reserve is set up, all claims to use this area are registered in order to provide a formal safeguard for the rights of the local population.
Legal status and management
The forest estate (285 000 ha) possesses a special status with regard to utilization and production. It is made up of different categories of woody vegetation cover, 83% in the closed high forest zone, 14% in the woodlands and 3% in the open areas and grasslands (14). By law, these forest reserves are available solely for forestry purposes, so that theoretically there should not be encroachment by agriculture. However, to some extent agriculture is nevertheless illegally practised in these areas, namely in the form of shifting cultivation (see also 2.1) (13). The actually gazetted forest reserves or forest estate are fully protected and controlled by the Forestry Division. The same regime applies to an additional area of 33 950 ha of proposed, but not yet legally constituted reserves (13) (14).
Forest reserves are logged (or being logged) (Gola, Mountains, Kambuis, Goboi, Dodo and Nimini Hills, Kasewe) or are envisaged for logging (Tama, Tonkali), or have largely protection functions (Peninsula Hills) or are made of small forest areas not suited for industrial exploitation. While the stocked forest reserves contain predominantly natural forests, some of the smaller ones also include, or consist mainly of plantations.
The ‘protected forests’ on chiefdom lands amount to 31 900 ha, of which 11 800 ha only correspond to forests larger than 80 ha (14). They consist mainly of strip plantations along roads and the erstwhile railway. They are protected and administered by the Forestry Division, the legal distinction with forest reserves lying in the different way in which the revenue accruing from exploitation is distributed (13).
While the forest reserves and protected forests can be used commercially, the protection forests serve largely to ensure protection of wildlife and vegetation. They cover a total area of 76 500 ha (13). However, the available information never mentions legally constituted restraints on possible exploitation, although regulating measures are foreseen (e.g. in game reserves). Unreserved forests are in no way whatsoever protected and are thus gradually alienated to other land uses.
Sustained yield in the natural forests is secured partly through natural regeneration. Since this does not suffice in many of the areas despite the prescribed cutting limits, silvicultural treatment has been undertaken on a small scale, e.g. through cutting of undergrowth and climbers or through enrichment and line planting. In poorly stocked forest reserves, intensive management as defined in this study is, however, very localized and restricted, and it has therefore been convened not to classify any significant area as “intensively managed”.
The most important forests are divided up into concessions, which are all in operation, with the exception of the Tama and Tenkoli forest reserves. Their utilization is regulated officially by a concession agreement only in the case of the Gola East and West forest reserves. Exploitation fees and royalties are paid to the central government, the paramount chiefs and the local landowners (13).
Approximately half of the present logging areas are situated inside forest reserves and the other half in salvage zones (14). Felling is done on a selective basis with fixed minimum girths for the respective species. The main forest blocks suitable for sawlog production in industrial quantities are situated in the eastern half of the country. More than 60 tree species are logged, of which the nine most important ones account for 70% of the total production: Mimusops heckelii, Terminalia ivorensis, Brachystegia leonensis, Oldfieldia africana, Berlinia confusa, Piptadeniastrum africanum, Didelotia idea, Tarrietia utilis and Ceiba pentandra (6) (9).
Total log production should reach 70 000 m3 in 1980, of which 50 000 m3 are transformed in the existing five sawmills, and the other 20 000 m3 are sawn in the forest by pit-sawyers, the latter producing roughly 10 000 m3 of sawn timber (13). Departmental statistics indicate that around 880 ha of natural high forest are being logged over annually inside concession areas (12).
There are currently no wood-based panel mills nor pulp and paper mills in Sierra Leone. Secondary wood industries consist so far only in a match factory and a few furniture industries. Building activities require an important volume of sawn timber. Local sawn timber production by the forest industry cannot yet satisfy the domestic market which has to be supported by imports.
Other forest products
Approximately 95% of the total roundwood production is used as fuelwood (about 2 500 000 m3). The market is mainly supplied by farmers who collect bundles of firewood and sell them at roadside. There is also a growing number of cutters around Freetown and a developing trade of fuelwood for tobacco drying at Makeni. Charcoal production plays only a minor role and should amount yearly to 30 000 m3 approximately (13). Production of building poles cannot be determined exactly. The FAO Yearbook of Forest Products gives an estimate of 105 000 m3 of ‘other industrial roundwood’, including poles, posts etc. for 1978. The estimate of fuelwood production is probably conservative because of the increasing crude oil prices and the fast population growth.
Important minor forest products are palm oil for local consumption, palm kernels and piassava for export. Only a negligible proportion originates from the forest estate, the bulk of it being obtained from farmlands. Other products include rubber, copal, kapok, poyok oil, loofahs (fibrous substance of the pod of Luffa aegyptiaca) and fibres from various species (2).
1.1.3 Present situation of the growing stock
In the absence of a recent national forest inventory, the growing stock in the natural forests of Sierra Leone has been estimated on the basis of rather old inventory results of the Gola, Tama and Tonkoli forest reserves (6) (7), and of more recently elaborated figures on merchantable volume (13) (14). These data cover only the commercial species, - 60 out of 200 - with a minimum diameter at breast height of 58 cm (6 feet girth) in sufficiently stocked zones. Ratios between volume of all species above 58 cm and the same volume of the merchantable ones and between volume of all species above 10 cm (VOB) and volume of all species above 58 cm, have been estimated from results of forest inventories in Ivory Coast, to arrive at the figures given in the following table.
Growing stock estimated at end 1980
(in million m3)
Since no data at all are available concerning the growing stock in the woodlands, the corresponding estimates calculated for Ghana and Togo have been used.. The total volume increment of all trees over 58 cm DBH in logged areas (NHCf1uc) is estimated at 1 m3/ha/year (13).
Early in this century plantations of export crops such as rubber, gum copal, oil palm and cola were established by the government and were taken over by the Forestry Department from its foundation in 1911. Planting of indigenous timber species was tried on an experimental basis up to 1929. Nursery and plantation techniques were developed between 1930 and 1940 with Gmelina arborea, Tectona grandis, Cassia siamea as well as with indigenous species such as Terminalia spp., Tarrietia utilis, Entandrophragma spp. and Nauclea diderrichii (4). The first plantation under the taungya system was established in 1931. The trees were either planted in pure groups, in pure lines cr in regular mixture. From 1935 on it was common practice to have Gmelina and local species in alternate lines. With the exception of teak, which was planted naked as stump, all standards were planted as striplings in baskets at 9 m by 9 m. Plants used as coppice e.g. Cassia, were spaced first at 2.30 m by 2.30 m and later on at 3 m by 3 m.
Between 1940 and 1947, closely spaced formal plantations were made in three centres: two had Cassia fuel plantations and the third was used for the production of poles and firewood. All other plantations in forest reserves were established on the principle of wide spacing, generally 18 m by 9 m, with natural secondary growth as a filler crop (1). Local administrations also became interested in forestry and began to create small ‘protected forests’, belts of young secondary growth not rich in valuable species but improved by line planting with valuable timber trees. In the fifties, a return to closer spacing and homogenity became apparent and plantations were undertaken on a moderately larger scale (5).
The great majority of the existing plantations were established through the taungya system, in cleared rain forest and bush fallow areas. A complete range of species have thus been planted, many on an experimental basis (pines, Eucalyptus, etc.). The usual taungya crop is rice, and only one crop is grown, so it is necessary to carry out one slashing of regrowth during the first year after planting (13). Virtually no man-made forests have been established in savanna areas.
Only about 40 ha of all plantations are private property, the rest belonging to the central government or the tribal authorities (8).
1.2.2 Areas of established plantations
A nationwide plantation inventory has been in progress since 1975. Much information is now available, in particular on the extent and location of the afforestation activities. The investigations to date have shown that of 7 604 ha planted before 1972, a total of 3 776 ha still exist and that before the end of 1977 another 2 268 ha had been planted (13). The present planting programme supported by the government is 400 ha per year concentrated in the Southern Province for sawlog production as well as 160 ha of fuelwood plantations in the Northern Province for tobacco drying. Assuming an implementation cum survival rate of 50% for man-made forests established after 1971, the total afforested area at end 1980 may be estimated at 5 800 ha. These plantations are in the form of small plots, 40 to 60 m in width and 1 to approximately 10 ha in size, distributed over the whole country alongside roads and trails (3).
These are mainly situated in the Eastern and Southern Provinces, and for roughly 52% composed of Gmelina arborea in pure or mixed stands and for 48% of Terminalia spp. and other broadleaved species, sometimes in experimental plantations (Cordia alliodora, Nauclea diderrichii, Heritiera utilis, Cedrela mexicana, C. odorata, Eucalyptus spp.). Small experimental plots of Pinus caribaea are also probably included in the figures (8) (13).
Areas of established industrial plantations estimated at end 1980
(in thousand ha)
|Age class||0–5||6–10||11–15||16–20||21–30||31–40||> 40|
|PHL 1||Terminalia spp. and others||0.46||0.49||0.60||0.40||0.39||0.10||0.01||2.45|
|PHH 1||Gmelina arborea||0.50||0.54||0.73||0.49||0.46||0.12||0.02||2.86|
|P..1 = PH.1||Total industrial plantations||0.96||1.03||1.33||0.89||0.85||0.22||0.03||5.31|
Only Terminalia ivorensis and Gmelina arborea are important. They have become dominant because of their ease of propagation and establishment and of their rapid growth under suitable conditions.
They are situated mainly in the north and consist mostly of Cassia siamea plantations. No figures are available. Since mention is made of this species in all available reports, the corresponding planted area as at 1977 has been estimated at 10% of the area given for all broadleaved species other than Gmelina. Plantation activities have increased drastically in the last years due to the need for fuelwood for tobacco drying (13).
Areas of established non-industrial plantations estimated at end 1980
(in thousand ha)
|Age class||0–5||6–10||11–15||16–20||21–30||31–40||> 40|
|P..2 = PHL 2||Cassia siamea and others||0.26||0.06||0.07||0.05||0.04||0.01||0.01||0.50|
The following table summarizes existing results of all plantation efforts made until the end of 1980
Areas of established plantations estimated at end 1980
(in thousand ha)
|Age class||0–5||6–10||11–15||16–20||21–30||31–40||> 40|
|PHL=PHL+PHL2||All hardwood sp. other than fast-growing||0.72||0.55||0.67||0.45||0.43||0.11||0.02||2.95|
|PHH = PHH1||Fast-growing hardwood species||0.50||0.54||0.73||0.49||0.46||0.12||0.02||2.86|
|P = PH||Total all plantations||1.22||1.09||1.40||0.94||0.89||0.23||0.04||5.81|
1.2.3 Plantation characteristics
Some of the results of the plantation survey in progress relate to the current stocking. It is certain that in many of the inventory plots the latter is smaller than what it could be because of critical failures, defective genotypes, poor tending, mortality and unrecorded removals. The oldest stands on good sites, which would be most valuable for yield studies, have had many of their trees felled by pit-sawyers. Furthermore, many of the plantations, particularly the Gmelina ones, are on sites which are clearly unsuitable and thus their yields are not significant (13).
The earliest record of the introduction of Gmelina dates from 1896. Trial plantations were started in 1932 when the species was grown in mixture with Terminalia ivorensis, T. superba, Afzelia sp. and teak. By 1936, Gmelina was planted pure and became the principal plantation species. The incidence of die-back in older stands has, however, been observed (5).
The normal method of growing the species in Sierra Leone is by planting stumps raised in a nursery. Direct sowing is exceptional. Fast growth is restricted to the young tree. From the age of 20 onwards, the growth capacity reduces considerably (13). Existing plantations have suffered from silvicultural neglect and many are on soils and site types quite unsuitable for fast growth. Older stands are often affected by heartrot and dieback almost always occurs on poor sites. Since the mid sixties, Gmelina has been widely planted in the smaller ‘protected forests’.
Being one of the indigenous species of Sierra Leone, Terminalia ivorensis is found throughout the high forest zone. The earliest attempt at planting was made in 1927. From 1930 to 1935 efforts were made to grow it in mixture with Cassia siamea, the latter to be exploited on a coppice rotation of six years and the Terminalia as standards planted at an espacement of 10 m by 10 m, to be cut at age 72. From 1940 onwards the species became popular and easily gained first place when from 1957 to 1963 it became the official policy to place 80% of all new plantations under Terminalia. However, the high failure rate resulted in a policy shift with again the emphasis on Gmelina (5). In planting Terminalia, both stumps and striplings are used, the latter being more susceptible to drought. Close spacing is not necessary for the species as it grows naturally straight and is self pruning, even in the open. Planting distance is 4.6 m × 4.6 m. In line planting the spacing is 4.6 m by 14 m or 18 m × 3 m according to circumstances (5). In pure stands, Terminalia ivorensis suffers from a variety of attacks due to insects, from a fungus causing cancer, from browsing by antilopes (young plantations) and from fire.
Provenance trials with Pinus caribaea var. hondurensis exist, but have suffered from failures or inadequate tending. The same applies to trials of Cedrela odorata and Cordia alliodora (13).
Quantitative data about plantation characteristics are presented in the following table.
|Species||Rotation (years)||M.A.I. per ha/year 1||Final cut 2||Planting distance||Thinnings 2||Source|
|Gmelina arborea||2m × 2m|
3m × 3m
|20–30||25 stems||3.5m×3.5m||150 stems||(3)|
|3.7 cm||25 stems|
|1.9 cm||25 stems|
|20||3.5 m3||70 m3||(13)|
|Terminalia spp.||35–40||1 cm||20 stems||3m×4.6m||150 stems||(5)|
|40||4.5 m3||180 m3||(13)|
|Cedrela odorata||2 cm |
|Cordia alliodora||1.5 cm|
|Tarrietia utilis||0.7 cm|
|Khaya spp., Entandrophragma spp. and Afzelia sp.||100||1 cm||(3)|
|Nauclea diderrichii||50–60||25 stems||2.4m×2.4m||(3)|
1 Either volume increment (in m3) or diameter increment (in cm)
2 Either in volume (m3) or in number of stems
2. Present trends
2.1 Natural woody vegetation
In the moist forest zone, shifting cultivation or “bush fallow” (10) (11), is the main factor of deforestation, other minor causes being overexploitation, mining and grazing. Rotational bush fallow is the most widely practised farming system in the country. The mean length of the fallow period is 8.8 years, but varies widely. In 1978, the average farm size had decreased to 1.3 ha and more than 75% of the farmers were at subsistence level. No definite crop sequence is followed. After clearing, the land is usually planted with upland rice in mixture with other crops. In most cases (64%) the land is then left to fallow. The system in itself is not harmful, provided the fallow periods are sufficiently long to permit the soil fertility to be restored to adequate levels by the slow natural processes. Demographic pressure, however, has disrupted the equilibrium and the resultant shortening of fallow cycles has lead not only to the reduction of productivity but also to irreversible soil degradation (11). An intricate pattern of various stages of forest destruction and regrowth thus exists, with predominance of low bush. A typical tree species present in these areas is Elaeis guineensis, fairly resistant to fire and seldom felled by the farmers, who tap it for the production of palm wine consumed locally (10).
The logging infrastructure in the remaining unreserved high forest attracts many farmers, and the resulting deforestation is estimated at 4 000 ha per year for the period 1976–80. The return to the land of people previously engaged in mining and the government's emphasis on increasing food production accentuate this influx. Experience has shown that the local population, regardless of existing legal restraints, continues to make use of its inherited rights in some forest reserves, which leads to a presumed annual loss of 400 ha of reserved forest.
Since reservation guarantees the existing rights of the local populace, and since no alternative areas on dry land are available for allocation to displaced farmers, the government is encouraging the farming of inland and mangrove swamps. This is responsible for an additional annual clearing of 1 400 ha of unproductive forests (2).
Comparison of aerial photographs taken during the periods 1958–1961 and 1975–1976 allows for the study of the progress of the deforestation. The great majority of the gazetted and proposed forestry reserves show signs of encroachment by cultivation to varying degrees. Notable exceptions are the Gola reserves (14).
The following table gives deforestation rates for the period 1976–80 and also estimates for the next five-year period. Intensification of inland swamp development will increase the rate at which the corresponding forests (NHCf2) are cleared (12). The remaining area of unreserved high forest on dry land (NHCf1) available for bush fallow generally after logging, is diminishing and corresponding deforestation should slow down.
Average annual deforestation
(in thousand ha)
Deforestation will continue widespread as a result of a persistent expansion of the requirements for cultivable land. However, except in isolated cases such as that of the Tama and Tonkoli reserves, the rate of deforestation does not appear alarmingly high and many of the major forest areas are not affected to a significant extent at least on the evidence of aerial photographs. Unreserved productive forest lands, however, are a rapidly diminishing asset, as large areas of such forest have been cleared in recent years to establish cocoa and coffee plantations (14).
In the moist savanna zone, grassland is burnt every dry season in order to stimulate the growth of fresh grass used as fodder, causing a change in the vegetation; this practice, closely linked to cattle grazing, leads to the development of more open tree savannas. Lophira sp. prevail in this zone due to its resistance to fire (10). The remaining bush is steadily degenerating. Shifting cultivation occurs also in the savanna zones, although to a much lesser extent than in the high forest zone. Generally speaking, no significant changes are expected in the next years, so that the areas of the various categories of open woody vegetation may be assumed unchanged.
2.1.3 Trends in forest utilization
Total log output in 1985 can be roughly estimated at 85 000 m3. The Tama and Tonkoli reserves may enter into production. An increase in the consumption of fuelwood to, say, 3 million m3 by 1985, is likely. No other significant changes are to be expected in the coming five years.
2.1.4 Areas and growing stock at end 1985
Areas and volumes have been calculated taking into consideration the deforestation rates for the period 1981–85, indicated under 2.1.1.
Areas of natural woody vegetation estimated at end 1985
(in thousand ha)
|204||204||506||710||3 880||140||1 175||1 315||415||3|
Growing stock estimated at end 1985
(totals in million m3)