2. Tendances actuelles
2.1 Végétation ligneuse naturelle
Le mode d'agriculture pratiqué au Gabon est encore presque exclusivement la culture sur brûlis. Les cultures pour l'exportation sont négligeables et les plantes cultivées sont surtout le manioc et le bananier destinés à l'alimentation locale. Encore ces cultures sont elles insuffisantes pour la faible population du Gabon. On pense qu'autrefois la population était plus importante et les cultures plus développées. D'immenses régions aujourd'hui complètement vides portent en effet la trace d'anciennes cultures. L'évaluation des superficies occupées actuellement par les cultures vivrières est de 150 000 ha environ (chiffre du Ministère de l'Agriculture). Les cultures durant en moyenne 3 à 4 ans, on peut estimer que l'espace défriché chaque année aux dépens de la forêt ou des jachères forestières représente environ 40 000 ha. A cela il convient d'ajouter quelques milliers d'hectares de défrichement de forêt ou de jachères forestières pour diverses raisons (plantations industrielles, plateformes de routes et chemins de fer, etc…). On aboutit ainsi à un chiffre extrêmement faible par rapport à la superficie totale couverte de forêts denses et de jachères forestières.
L'estimation de la proportion des forêts denses dans la surface défrichée annuellement est difficile à faire. Elle doit prendre en compte le fait que la population est concentrée le long des axes routiers et qu'elle utilise les jachères forestières accessibles à proximité de ceux-ci, de préférence aux forêts denses plus éloignées (48) (51). Par ailleurs il convient de remarquer que, contrairement à ce qui se passe dans les pays forestiers plus peuplés de l'Afrique de l'ouest, on n'assiste pas à l'invasion des massifs intacts par la population utilisant le réseau des routes d'exploitation forestière comme moyen de pénétration. Sur la base de ces observations on peut considérer en première approximation que les forêts denses (NHCf) sont défrichées dans la proportion d'un tiers de l'ensemble des défrichements, soit 15 000 ha environ par an. La quasi-totalité de cette surface est prise sur les forêts productives déjà exploitées (NHCf1uc).
Le Gabon est donc l'un des rares pays forestiers tropicaux au monde où la forêt ne soit pas vraiment menacée par les défrichements agricoles.
Déforestation annuelle moyenne
(en milliers d'ha)
1976–80 et 1981–85
Sur le plan qualitatif, l'action des défrichements agricoles conduit à une modification radicale des peuplements de recolonisation par rapport aux peuplements initiaux. Ceci est dû tout d'abord à la sélection opérée lors de l'abattage du fait des difficultés de l'abattage de certains bois: dureté (Lophira alata, Nauclea trillesii, Guibourtia tessmannii), présence de contreforts (Desbordesia glaucescens, Klainedoxa gabonensis), diamètre élevé (Ceiba pentandra, Piptadeniastrum africanum); intérêt de l'essence pour la médecine traditionnelle ou la nourriture: fruits, écorces, feuilles (Irvingia gabonensis, Coula edulis, Poga oleosa, Cylicodiscus gabunensis); respect religieux: Distemonanthus benthamanius (movingui). En second lieu, cette modification est due au tempérament héliophile des espèces qui repoussent dans les brousses secondaires et qui se mêlent aux rejets de souche (okoumé, parasolier, nombreuses Euphorbiacées telles que les Macaranga et les Croton, Myristicacées à bois tendre, Annonacées, fromagers). A l'ombre de ces arbres s'installent ensuite les semis d'essences d'ombre à bois plus dur, qui éliminent à leur tour, mais lentement, les précédentes. L'okoumé cependant parvient, grâce à sa taille élevée, à se maintenir jusqu'à un stade avancé du vieillissement de la forêt.
Ainsi, à mesure que s'écoule le temps passé depuis le défrichement, la composition de la forêt se modifie. L'examen de la composition d'un peuplement permet de reconstituer son histoire et de dater approximativement le dernier défrichement.
Cependant, on constate de plus en plus une certaine stabilisation des villages et des cultures le long des routes. Les défrichements ont tendance actuellement à parcourir des zones déjà défrichées à une date récente (parmi lesquelles de nombreux jeunes peuplements d'okoumé qui se sont installés sur les anciennes cultures, ce qui est très regrettable), tandis que la plus grande partie de la forêt est abandonnée à elle-même et à son évolution naturelle vers la prédominance des essences d'ombre.
Il est intéressant de noter certains processus de reforestation naturelle au contact forêt-savane. Dans le secteur des savanes de la région de Franceville, la progression de la forêt frappe tous les observateurs. De jeunes okoumés s'installent au milieu des études herbeuses au arbustives. Les feux contiennent cepandant cette expansion (8) (16). Dans les savanes littorales on note également une incontestable progression de la forêt favorisée par la dépopulation de ces zones au profit de Libreville et Port Gentil. La savane est envahie par des lianes, puis par des semis d'okoumés ou d'evino (Vitex pachyphylla). Dans la région du Moyen Ogooué, la forêt progresse également. Dans la région du Bam Bam, tous les observateurs ont remarqué que la forêt suivait la progression du front d'érosion des cirques. Dans la région de Mandji, l'avance de la forêt est incontestable (jeunes plantes d'ozouga, de ngong mebane) et les feux n'entament pas le tapis broussailleux qui succède à la savane et précède la forêt.
Bien qu'on ne puisse parler véritablement de dégradation des formations forestières par l'exploitation du bois d'oeuvre il est intéressant d'indiquer quelle est son incidence sur leur volume et leur composition. L'exploitation forestière telle qu'elle est pratiquée actuellement aboutit à une production de 10 m3 par hectare de bois commercial, ce qui représente environ 20 m3 de bois sur pied. Si l'on ajoute les défrichements pour ouverture de piste, parcs et campements, on obtient un total d'environ 30 m3 à l'hectare au maximum. Ce chiffre est à comparer aux 200 à 300 m3 de bois sur pied (arbres de 10 cm et plus de diamètre) présents dans la forêt. L'exploitation forestière ne modifie donc pas de façon sensible les réserves quantitatives de la forêt. Elle a cependant deux conséquences importantes: d'une part l'ouverture dans le peuplement de trouées suffisamment importantes favorise les espèces héliophiles dont les semenciers existent alentour, et, d'autre part, la composition qualitative de la forêt est modifiée par écrêmage des meilleurs arbres appartenant aux meilleurs espèces (ou tout au moins considérées actuellement comme telles).
Il ne semble pas que les feux de brousse dans les savanes ait une incidence significative sur la synusie ligneuse, comme cela est le cas dans les régions guinéo-soudaniennes et soudaniennes. Tout au plus peut-on mentionner leur action retardatrice sur les processus de reforestation naturelle des lisières signalés plus haut.
2.1.3 Tendances dans l'exploitation forestière
On peut espérer que dans l'avenir la diversification des essences exploitées ira en s'accroissant. Ce n'est cependant pas une évolution qui se dessine pour un avenir proche au Gabon (contrairement, par exemple, au Cameroun, à la Côte-d'Ivoire et, dans une moindre mesure, au Congo). Ceci s'explique par la prédominance de l'okoumé dont le Gabon s'est fait une “spécialité” et qui handicape l'ouverture du marché vers d'autres essences. Seule une industrialisation plus importante du secteur bois pourrait permettre cette diversification. Pour la projection de la situation en 1985 (cf. tableaux du paragraphe 2.1.4) on a supposé que le volume extrait à l'hectare (VAC) serait en moyenne de 12 m3 pour la période 1981–85 en augmentation de 20% par rapport aux années précédentes (cf. paragraphe 1.1.3).
Quant au niveau global de l'exploitation forestière au Gabon, on peut tout au plus espérer un accroissement de la production, de l'ordre de 5% par an en ce qui concerne le bois d'oeuvre. Ceci correspond à une production de 1 800 000 m3 en 1985 (à partir d'une production de 1 400 000 m3 en 1980). La surface exploitée de 1981 à 1985 serait donc ainsi de l'ordre de 675 000 ha au total.
Le projet de création d'une usine de pâte à papier à Kango sur le fleuve Como au fond de l'estuaire du Gabon, à 70 km du port d'Owendo, mérite d'être mentionné. La Société Cabonaise de Cellulose (SOGACEL) dont le capital appartient en majorité à l'Etat gabonais, et dont les partenaires privés principaux sont étrangers, continue depuis déjà plus de 17 ans les travaux préparatoires (inventaire forestier, essais de laboratoires et essais en vraie grandeur de réalisation de pâte blanchie au sulfate des bois feuillus tout-venant, essais d'exploitation de la forêt naturelle, essais de replantation en essences à croissance rapide). Le projet a connu de 1976 à 1979 une phase de préréalisation avec l'installation d'un chantier pilote d'exploitation, et d'un chantier pilote de reforestation et la création de la base de Kango (construction des terrassements, des routes, des logements, des ateliers et début de la formation des futurs ouvriers de l'usine). L'année 1980 à été marquée par un temps mort dans la réalisation du projet qui devrait redémarrer en 1981. La capacité prévue de l'usine est de l'ordre de 200 000 tonnes de pâte par an, nécessitant l'exploitation de 900 000 m3 à 1 000 000 m3 de bois rond par an. Cette exploitation serait menée sur 7 chantiers regroupés en deux bases secondaires. La superficie annuellement exploitée serait de l'ordre de 5 000 à 7 000 ha par an (le volume utile pour la pâte à papier étant estimé de 140 à 180 m3/ha). L'exploitation de la forêt naturelle est programmée pour durer 20 ans puis être ensuite remplacée par le bois provenant des plantations forestières qui seront réalisées dès la première année sur une superficie de 2 000 ha par an.
2.1.4 Surfaces et volumes sur pied à la fin de 1985
Compte tenu de ce qui précède, la situation en 1985 devraît être sensiblement la suivante.
Surfaces de végétation ligneuse naturelle estimées à la fin de 1985
(en milliers d'ha)
Volumes sur pied estimés à la fin de 1985
(en millions de m3)
Il a été question à plusieurs reprises au cours des dernières années du lancement d'un nouveau programme de plantations d'okoumé. Il ne semble pas cependant que ce programme puisse démarrer avant 1985 compte-tenu de l'insuffisance des moyens mis à la disposition du service forestier gabonais.
Dans le cadre du projet SOGACEL il est prévu (cf. paragraphe 2.1.2) la réalisation d'un programme de 40 000 ha de plantations de pins et d'eucalyptus à raison de 2 000 ha par an pendant 20 ans. La productivité moyenne attendue étant de 25 m3/ha/an à l'âge de 20 ans soit 500 m3/ha à 20 ans, ces plantations produiront 1 000 000 de m3 par an. Si on envisage un relancement du projet en 1981 comme prévu on peut espérer le rythme de reboisement suivant: 500 ha en 1982, 1 000 ha en 1983, 1 500 ha en 1984, et 2 000 ha en 1985, soit 5 000 ha au total dont 4 000 ha d'eucalyptus et 1 000 ha de pins.
Surfaces estimées des plantations (industrielles) réalisées à la fin de 1985
(en milliers d'ha)
|Classe d'âge||0–5||5–10||11–15||16–20||21–30||31–40||> 40|
|PHL = PHL 1||Aukoumea klaineana||1||5||11||2||19|
|PHH = PHH 1||Eucalyptus spp.||4||4|
|PH = PH.1||Sous-total essences feuillues||4||1||5||11||2||23|
|PS = PS.1||Pinus spp.||1||1|
|P = P..1||Total toutes plantations||5||2||5||11||2||24|
Chevalier, A. 1916 “La forêt et les bois du Gabon” - Paris
Heitz, H. 1943 “La forêt du Gabon” - Paris
Roquebain, C. 1946 “Notes sur le Gabon” - Bulletin de la Société Géographique Française -Paris
Aubréville, A. 1948 “Etude sur les forêts de l'A.E.F. et du Cameroun” - Paris
Bernard, F. 1954 “Les inventaires systématiques et les formations forestières au Gabon” - Section de Recherches Forestières - Libreville
Bernard, F. 1954 “La composition de la forêt au Gabon et quelques formations définies en forêt dense” - Section de Recherches Forestières - Libreville
Lassere, G. 1955 “Okoumé et chantier forestiers au Gabon” - Cahiers de l'Outre-Mer - Tome VIII
Section de Recherches Forestières/CTFT 1955 “Contribution à la connaissance de la richesse en bois commerciaux de la forêt du Gabon” - Nogent-sur-Marne (France)
Koechlin, J. 1957 “Evolution de la végétation dans la zone forestière rizicole de Tchibanga”
Walker, A. et Sillans, R. 1961 “Les plantes utiles du Gabon” - Editions Lechevalier -Paris
De Saint-Aubin, G. 1963 “La Forêt du Gabon” - Centre Technique Forestier Tropical -Nogent-sur-Marne (France)
Centre Technique Forestier Tropical 1964 “Inventaire papetier de la zone de Kango” -Nogent-sur-Marne (France)
Chatelin, Y. 1964 “Notes de pédologie gabonaise” - Office de la Recherche Scientifique et Technique d'Outre-Mer - Paris
Gazel, M. 1964 “Inventaire des plantations d'okoumé de la Nkoulounga” - Centre Technique Forestier Tropical - Libreville
Hallé, N., Le Thomas, A. et Gazel, M. 1967 "Trois relevés botaniques dans les forêts de Belinga - Biologa gabonica III
FAO 1968 “La législation forestière du Gabon” - par T. François - Rome
Direction des Eaux et Forêts 1969 “Développement de l'économie forestière de 1966 à 1968” - Libreville
Bouquerel, J. 1970 “Le Gabon” - Presses Universitaires de France - Paris
Centre Technique Forestier Tropical 1970 “L'okoumé dans les savanes du Haut Ogooué” - Libreville
Centre Technique Forestier Tropical 1970 “Inventaire papetier complémentaire” - Nogent-sur-Marne (France)
Centre Technique Forestier Tropical 1970 “Inventaire forestier dans la région de Lambaréné”- Nogent-sur-Marne (France)
Direction des Eaux et Forêts 1970 “Note sur la forêt du Gabon” - Libreville
FAO 1970 “Evaluation des I et II zones forestières” - FO: SF/GAB 6 - Rapport technique 1 - sur la base des travaux de G. Gloriod - Centre Technique Forestier Tropical - Nogent-sur-Marne (France)
FAO 1970 “Diamètre et valeur des okoumés” - FO:SF/GAB 6 - Rapport technique 2 - sur la base des travaux de B. Vannière - Centre Technique Forestier Tropical - Libreville
Lanly, J.P. 1970 “Instructions techniques pour l'éxécution des inventaires dans le centre- est et l'est du Gabon” - Rapport de consultant - Libreville
Centre Technique Forestier Tropical 1971 “Potentiel des principales essences du Gabon aptes à l'emploi en traverses de chemin de fer” - Nogent-sur-Marne (France)
FAO 1971 “Marché des bois du Gabon” - FO: SF/GAB 6 - Rapport technique 4 - sur la base des travaux de E. Uhart - Centre Technique Forestier Tropical - Libreville
FAO 1971 “Etude sur l'aménagement de la forêt de la Mondah” - FO: SF/GAB 6 - Rapport technique 5 - sur la base des travaux de B. Vannière - Centre Technique Forestier Tropical - Libreville
FAO 1971 “Etude sur l'aménagement de la forêt des lacs du nord” - FO: SF/GAB 6 - Rapport technique 6 - sur labase des travaux de B. Vannière - Centre Technique Forestier Tropical - Libreville
FAO 1972 “Etude du limba dans le nord-est du Gabon” - FO: SF/GAB 6 - Document de travail 3 - préparé par L. Baumgartner - Centre Technique Forestier Tropical - Libreville
FAO 1972 “Croissance de l'okoumé en troisième zone” - FO: SF/GAB 6 - Document de travail 4 - préparé par J. Geiser - Centre Technique Forestier Tropical - Libreville
Direction des Eaux et Forêts 1973 “Statistiques de production et commercialisation des bois” - Libreville
FAO 1973 “Sondages dans la forêt du sud-est du Gabon” - FO: SF/GAB 6 - Document de travail - Centre Technique Forestier Tropical - Libreville
FAO 1973 “Pré-Inventaire” - FO: SF/GAB 68/506 - Rapport technique 18 - Centre Technique Forestier Tropical - Libreville
Leroy-Deval, J. 1973 “Sylviculture de l'okoumé - Maladies et défauts” - Centre Technique Forestier Tropical - Nogent-sur-Marne (France)
Leroy-Deval, J. 1973 “Note sur la limite de l'aire de l'okoumé dans le nord-est du Gabon” - in Bois et Forêts des Tropiques - No. 151 - Nogent-sur-Marne (France)
Clément, J.C. et Guellec. J. 1974 “Utilisation des photographies aériennes au 1/5 000 en couleur pour la détection de l'okoumé dans la forêt dense du Gabon” - in Bois et Forêts des Tropiques - No. 153 - Nogent-sur-Marne (France)
FAO 1974 “Etude des lots de la zone d'attraction du chemin de fer transgabonais” - FO: SF/GAB 6 - Document de travail 2 - Centre Technique Forestier Tropical - Libreville
FAO 1974 “Etude du secteur d'aménagement M'Voum-Noya” - FO: SF/GAB 68/506 - Rapport technique 16 - Centre Technique Forestier Tropical - Libreville
FAO 1974 “Carte au 1/50 000 de la végétation de l'est du Gabon” - FO: SF/GAB 6 - Rapport technique 19 - Centre Technique Forestier Tropical - Libreville
Gloriod, G. 1974 “Les forêts de l'est du Gabon” - in Bois et Forêts des Tropiques No. 155 - Nogent-sur-Marne (France)
FAO 1975 “Perspectives d'aménagement forestier pour l'ensemble du Gabon” - FO: SF/GAB 68/506 - Rapport technique 15 - Centre Technique Forestier Tropical - Nogent-sur-Marne (France)
FAO 1975 “Inventaire forestier dans le centre-est du Gabon” - FO: SF/GAB 68/506 - Rapport technique 17 - Centre Technique Forestier Tropical - Nogent-sur-Marne (France)
Nicolas, P. 1977 “Contribution à l'étude phytogéographique de la forêt du Gabon” - Centre National de la Recherche Scientifique - Paris
Centre Technique Forestier Tropical 1978 “Inventaire sur les chantier I (550 ha) et II (750 (750 ha)” - par J. Clément et M. Vernay - Nogent-sur-Marne (France)
Centre Technique Forestier Tropical 1978 “Inventaire forestier dans la zone d'Edenzork” - par J. Clément et Y. Nouvellet - Nogent-sur-Marne (France)
Centre Technique Forestier Tropical 1979 “Ressources en bois du Gabon - Mise en évidence des volumes commercialisables” - par J. Estève - Nogent-sur-Marne (France)
FAO 1979 “Aménagement du massif de Fougamou” - FO: DP/GAB/73/002 - Rapport technique 1 - sur la base des travaux de J. Clément et J.L. Guérin - Centre Technique Forestier Tropical - Nogent-sur-Marne (France)
FAO 1979 “Aménagement du massif du Sud-Estuaire” - FO: DP/GAB/79/002 - sur la base des travaux de J. Clément et J.L. Guérin - Centre Technique Forestier Tropical - Nogent-sur-Marne (France)
FAO 1979 “Mise en valeur forestière du Fernan-Vaz” - FO: DP/GAB/73/002 - Rapport technique 3 - Centre Technique Forestier Tropical - Nogent-sur-Marne (France)
FAO 1979 “Projet d'aménagement agrisylvicole dans la Ngounie” - FO:DP/GAB/73/002- Document technique 1 - sur la base des travaux de G. Guigonis - Centre Technique Forestier Tropical - Nogent-sur-Marne (France)
FAO 1979 “Développement forestier (troisième phase)” - FO: DP/GAB/73/002 - Rapport final - Centre Technique Forestier Tropical - Nogent-sur-Marne (France)
Direction Générale des Eaux et Forêts 1980 Lettre du Directeur Général des Eaux et Forêts au Directeur de la Division des ressources forestières de la FAO en date du 4 Mars 1980 - Libreville.
The Gambia extends along the river of same name, running in an east-west direction at the average latitude of 13'30 N, and cutting across Senegal over 330 km. The country covers a total area of 1 040 000 hectares. It is very level with an altitude not exceeding 50 m. Average annual rainfall ranges between 900 and 1 100 mm, except in the south-western part (western division and Banjul and Kambo districts) where it can reach 1 400 mm in some localities. There is one single intense wet season of five months (June–October) juxtaposed with a seven-month dry season (5).
Total population numbered 494 000 inhabitants in the 1973 census, growing at an estimated rate of 2.0 per cent corresponding to 570 000 inhabitants approximately in 1980. With a population density of 55 inhabitants per km2, the Gambia is the fifth most densely populated country of Africa (7). The total male adult rural population numbered 112 000 in 1973 (5) or 125 000 approximately in 1980. Population pressure on vegetation is therefore high and vegetation has been subjected to serious degradation during the last decades.
1. Present situation
1.1 Natural woody vegetation
1.1.1 Description of the vegetation types
Closed broadleaved forests (NHC)
The only closed forests present in The Gambia correspond to special edaphic conditions. The mangroves penetrate deep along the Gambia and its tributaries. The typical succession is described in (5) (after Giglioli and Thornton) as follows: “each saline water course is characteristically bordered up to the limits of daily tidal flooding by a gallery of tall Rhizophora racemosa. Inside the gallery up to the mean limits of inundation by spring tides are found woodlands of Avicannia africana. Rhizophora harrisonii and R. mangle occur at the boundary between the R. racemosa and A. africana stands”. R. racemosa appears to be the pioneer species and being replaced later on by A. africana until the soil raised becomes too arid to support vegetation during the dry season and constitutes salty barren flats (called “tanns” in Senegal). At present both types of mangroves are used by villagers for fencing poles and in house construction, and for fuelwood either for local consumption or for sale in Banjul (3).
Gallery forests - “riparian woodland” according to (5) - are found along the streams above the limit of tidal waters. They contain the bulk of the most useful commercial timber species, particularly mahogany (Khaya senegalensis), Chlorophora regia (trade name: ircko) and other tree species such as Parinari excelsa and Leguminosae like Detarium senegalense, Dialium guineense and Erythropheum guineense.
Open broadleaved forests (NHc/NHO)
Practically all the woody vegetation of the country is constituted by a mixture of more or less degraded facies of mixed forest-grassland formations of varying heights and densities. There does not seem to remain significant areas of (dense) woodland at present since their total area was estimated at 7 500 ha from the 1968 photographs (6) and they were found on soils “suitable with qualifications” for agriculture (5). The remaining open mixed forest-grassland formations are termed differently according to the authors. (5) distinguishes mainly:
“parkland” or “woodland savanna” in frequently farmed areas with Parkia biglobosa, Daniellia oliveri (in the west), Bombax buonopusense, and without shrubs;
“disturbed woodland with shrub understorey” with Combretacese (Combretum micranthum, Guiera senegalensis, Anogeissus leiocarpus, Terminalia spp.), and Leguminosae species (Cordyla pinnata, Cassia siberiana, Swartsia madagascariensis, Prosopis africana and Acacia spp.) and presence of a bambou (Oxytenanthera abyssinica);
“Mitragyna - Acacia scattered tree savanna”.
Other classifications are found which are difficult to correlate with the one above and between them, for instance in document (4) which distinguishes among tree formations “woodland savanna” and “savanna”, and in document (6) where the open vegetation types with trees are termed: “woodland savanna”, “tree/shrub savanna”, “open tree/shrub savanna”.
Most common palm species are Elaeis guineensis and Borassus aethiopium (rhun palm).
Shrub formations (nH)
Formations with shrubs as the main woody elements are also termed differently by the various authors. (5) distinguishes shrub communities in drainage depressions and alluvial areas with Mitragyna inermis and Acacia seyal and as coastal vegetation with Parinari macrophylla. The classification given in (6) tends to use extensively the concept of shrub with the following classes: “shrub woodland”, “shrubland with occasional trees” and “shrub savanna”. Shrubs and/or small stunted trees are the dominant woody element of the classes “thorn and small tree areas” and “low bush/shrub and eroded areas” of the classification used in (4).
1.1.2 Present situation of the woody vegetation.
The diversity of concepts and classifications used and the importance of disturbance by agriculture do not allow for an easy breakdown of areas within the various categories used in this study, except for the closed forest ones (mangrove and gallery forests). A first compilation of the documents (4), (5), (6) and (7) have lead to the following estimates at end 1971 (1972 serial photographs).
|Vegetation and land-use classes||Code||Area|
(in thousand ha)
|Undisturbed woody vegetation:||mangroves||NHCf||64|
|productive woodlands||NHc/NHO 1||11|
|improductive tree and shrub formations||NHc/NHO 2i nH(part)||351|
|Undisturbed non woody vegetation|
(including coastal vegetation)
|Fallow areas||NHc/NHO a nH(part)||355|
|Roads, settlements, streams (excluding the Gambia river)||-||28|
|Total country||1 040|
These estimates have then been processed further and updated at end 1980 (9 years time lag) and the results are summarized in the following table:
The following explanations are useful for a better understanding of this table:
the category “logged-over productive closed broadleaved forests not intensively managed” (NHCf1uc) is made up of the gallery forests which are supposed to be left by 1980. The area of closed forests was estimated at 7 200 hectares for the whole country from the 1968 aerial photographs (7). Johnson assessed their area from the 1972 photographs at 2 500 hectares in the western division and the Kiang West district which cover in total a quarter of the whole country and are the most heavily forested areas of the country (7). An extrapolation to the whole country would give an order of magnitude of 5 000 ha, account being taken of deforestation during the last nine years;
mangroves are classified as closed broadleaved forests unproductive for physical reasons (NHCf2(i) since they do not produce wood for industrial processing). Their total area was estimated at end 1967 (1968 aerial photographs) at 66 500 hectares approximately (3) (6) (7), with 28 750 hectares of Rhizophora stands and 37 750 hectares of Avicennia. Assuming a 500 hectares annual deforestation rate during the last 13 years, a total area of 60 000 hectares can be estimated at end 1980;
fallow deriving from closed forests are probably negligible (NHCa);
as already mentioned in the previous section the area of dense woodlands left at present is most likely unsignificant (NHc/NHO1);
because of the differences between the various vegetation classifications used in The Gambia, it has been most difficult to distinguish between unproductive open broadleaved forests (NHc/NHO2 i), fallow formations derived from these types (NHc/NHO a) and (essentially) shrub formations either undisturbed or in fallow (nH). The estimates given in the table are essentially derived from the assessments and descriptions made in (5) and (7). Shrub areas would amount to 360 000 hectares, of which more than half would be fallow land.
All the figures given in this table, except those corresponding to closed forests and dense woodlands, must be considered as very tentative in the absence of a vegetation and land-use map using a meaningful classification. The most useful study presently available is based on a classification by soil associations, not by vegetation types (5).
There is no individual or collective ownership of land in The Gambia outside of Banjul and Kombo St. Mary (5). Consequently there is no privately owned forest and all forest land outside of Central Government demarcated and gazetted “forest parks” (see below) “may be broadly defined as communal land administered on behalf of the people” (2).
Legal status and management
In the fifties the Forestry Department was engaged in creating a forest estate (5). The number of forest parks thus gazetted has been reduced now to 66 (1) (2) (5), and the work of boundary maintenance, fire protection and early burning has been handed over to Area Councils. Their distribution according to the object of management is the following (5):
12 rhum palm (Borassus aethiopicum) forests totalling 618 ha;
14 timber forests totalling 4 104 ha;
6 bamboo (Oxytenanthera abyssinica) forests totalling 7 068 ha;
34 protection forests totalling 22 239 ha.
None of the forest parks includes mangrove forests. Interpretation of 1972 serial photographs showed that 3 758 ha, out of the total area of 34 029 ha, had been cleared for farming.
Forest plantations are established within the forest parks, of which 7 550 ha (or 22%) have been assessed as suitable for plantation (5). Despite their denomination these forest reserves have a productive function and are thereby not classified as areas unproductive for legal reasons (NHCf2r = NHc/NHO2r = O, although a small “nature park” at Ahuko near Banjul would probably correspond to this category).
Several silvicultural techniques in natural forests were used in the early stages, such as enrichment planting (see section 1.2.1) and thinning and high pruning of natural stands of Daniellia oliveri. These attempts have been discontinued and there are no working plans involving any sylvicultural treatment, that is no intensive management in the sense of this study.
Logging is carried out by the Forestry Division to supply its sawmill in Nyamba, western division. With this exception, most of the timber is produced locally by pitsawyers who use mahogany for the production of planks (5). It was estimated in the early 60's that there were 30 pairs of pitsawyers (1) and seven pitsawing units are mentioned in the early 70's (3). Taking a recovery factor of 0.4, the total log production for sawnwood and hewnwood could be in the early 70's equivalent to 8 450 m3.
|Consumer group||Sawn/hewn wood|
|Forestry Division sawmill||646||1 620|
|Villagers||2 350||5 870|
|Boat building industry (Banjul)||116||290|
|Total||3 381||8 450|
Approximately 2 100 m3 of sawnwood had to be imported in 1972/73 to satisfy local demand.
Other forest products
(3) gives a detailed survey of wood consumption in the country. For most items, local consumption corresponds to production.
|Roundwood requirements after felling|
|Fencing (household)||19 450|
|Industrial, social and service||400|
|Subtotal poles||33 650||34 000|
|Rhun palm||Household||8 050|
|Industrial, social and service||950|
|Subtotal Rhun palm||12 700||31 000|
|Fencing (household)||1 700|
|Industrial, social and service||100|
|Subtotal bamboo||8 450||8 500|
|Fuelwood and charcoal||Household||664 500|
|Cottage industry||53 850|
|Industrial, social||66 050|
|Subtotal fuelwood and charcoal||784 400||784 400|
The per capita household consumption of fuelwood and charcoal was in the early 70's of the order of 1.35 m3. There were already at that time supply shortage of bamboo and rhun palm. Thinnings from Gmelina plantations are already used as fencing posts and splits, and small quantity sawn for crates.
1.1.3 Present situation of the growing stock
Gross stem volume (VOB), per hectare and total, have been estimated only for the closed forests, i.e. mangroves and gallery forests. Gross stem volume of mangroves has been derived from the results of the inventory of 8 700 ha of mangrove in the central part of the country (8). It has been estimated at 80 m3/ha (weighted average for Rhizophora stands - 116 m3/ha - and Avicennia stands - 15 m3 approximately), a figure much higher than the ones habitually provided (for instance the same concept of volume was found to be 50 m3 in 7 000 ha of mangroves in Casamance). For gallery forest a tentative figure of 65 m3 derived from the inventory of 131 000 ha of forests and woodlands in a neighbouring area of Casamance.
Growing stock estimated at end 1980
(in million m3)
|NHC f1uv||NHC f1uc||NHC f2||NHc/NHO 1|
Seeds of Gmelina arborea were introduced to The Gambia in 1951 from Sierra Leone in a forest nursery sited at Cape St. Mary and transferred in 1953 to Yundum, both locations in the western division and close to Banjul (1) (9). In the fifties enrichment planting, first at regular espacement and then by group planting, of Gmelina arborea, Khaya senegalensis and Chlorophore excelsa (plots of 0.1 – 0.4 ha) was tried successfully in Nyambai forest park, as well as direct sowing of rhun palm seeds in selected forest parks, after complete clearing of the natural vegetation and in collaboration with groundnut farmers in a modified taungya system (1) (9). This latter has been used extensively from 1959 in forest parks of Nyambai, Bamba and Kabafita of the western division and had resulted at 1977 in the planting of 800 ha of Gmalina arborea and a small area of Tectona grandis (5) (9). Many other species have been experimented and/or planted on a very small scale since 1951 as Albisia lebbek, neem (Asadirachta indica), Eucalyptus spp., Terminalia spp., and a bamboo, Dendrocalamus strictus. However the main species planted by far remains Gmelina arborea which shows good growth, despite some damage in young plantations by monkeys (1).
1.2.2 Areas of established plantations
The estimates given below are compiled from documents (1),(2),(5),(6),(9) and (10). All existing plantations have been classified as industrial plantations since final cut, at least, is to be used as sawnwood, with the exception of small plantations of bamboo and of species for fuelwood.
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 1||Various species 1||0.05||0.05||0.05||0.05||ε||0.2|
|PHH 1||Gmelina arborea||0.3||0.2||0.15||0.45||ε||1.1|
|P=P..1=PH.1||Total (industrial hardwood) plantations||0.35||0.25||0.20||0.5||ε||1.3|
1 They include mainly teak and indigenous and exotic species for sawnwood and veneer such as Asadirachta indica, Chlorophora regia, Khaya senegalensis, Terminalia superba, T. ivorensis.
2 Some other fast-growing species have been tried and/or planted on a very small scale such as Albisia lebbek, Eucalyptus spp., and Dendrocalamus strictus (for some species, not strictly for industrial purposes).
1.2.3 Plantations characteristics
(6) mentions that Gmelina “plantations can have an increment rate as high as 18 m3/ha/year”. In (10) it is said that “mean annual increment for 10 to 20 years old stands seems to range from 15 to 20 m3/ha/year”.
2. Present trends
2.1 Natural woody vegetation
The study reported in (4) indicates a reduction of the “two-storey forest” from 28.85% in 1946 down to 3.40% in 1968 of the total area of twenty samples (51 800 ha or 5% of the total area of the country). Extended to the whole country it would mean a reduction of closed forest area between 1946 and 1968 from 299 000 ha to 35 000 ha. The area of closed forests other than mangroves was estimated at 7 200 ha from the 1968 aerial photographs. The part of mangroves included in this survey should amount approximately to 28 000 ha and, since mangroves have been reduced relatively little, this would mean that the total decrease would be of the order of 270 000 - 7 000 = 263 000 ha in 21 years or 12 500 ha per year. This figure is quite high and is also difficult to interpret as it is not known exactly what is meant by “two storey forest”. Dense forests other than mangroves are certainly now restricted to the banks of the main streams as gallery forests and are being reduced at an annual rate commensurate with their total size. A figure of 200 ha of gallery forest cleared per year has been eventually adopted.
It seems that mangrove forest areas are being slightly encroached on for rainfed rice production as mentioned in (6) and (8).
In addition it can be reasonably assumed that the proposed anti-salinity barrage at Yelitenda (lower river division) will in the long term kill the 8 700 ha of mangroves above it, and that they would have to be felled and utilized (8), probably during the next five years. As an order of magnitude it can therefore be assumed that a total of 10 000 ha of mangroves will disappear during this period.
Average annual deforestation
(in thousand ha)
|1976 – 80||1981 – 85|
Clearing of woodlands and shrublands for agriculture is going rapidly according to the study reported in (4) which provides the following results from the 5% sample area mentioned above:
Changes in land-use and vegetation cover
(in % of total sample area)
|Land-use and vegetation classes||1946||1968|
|“Woodland savanna” (50–75% canopy cover)||31.3||4.6|
|“Savanna” (25% cover)||14.0||17.6|
|“Thorn and small tree areas”||7.8||31.7|
|“Low bush/shrub and eroded areas”||0.4||19.9|
|“Cropping with natural fallow”||17.6||5.5|
|“Virtually continuous cropping”||-||17.3|
An interpretation of these results and an attempt to reconcile these figures with other data found in (5) and (7) lead to the conclusion that 6 000 ha are added annually to the total fallow area (NHc/NHO a and part of nH) at the expense of present open woodlands (NHc/NHO 21) and natural shrublands (part of nH).
Annual fires and overexploitation for fuelwood are impoverishing woodlands by reducing their density and eliminating progressively less fire-resistant species as in all mixed forest-grassland formations in Africa (5), the more so as population pressure is particularly high. As far as mangroves are concerned, Johnson, quoted in (5), concludes that fuelwood removal and the rate of growth of the smaller mangroves appear to be in equilibrium.
2.1.3 Trends in forest utilization
Estimated consumption level in 1985 as found in (3), and after correction by the results of the 1973 population census, is 1 251 000 m3 to compare with the corresponding figure of 878 000 m3 in 1973, that is an increase of 42% over 12 years. The supply being already tight or insufficient for some forest products, the per capita level of consumption (1.78 m3 of which 1.35 m3 of fuelwood) may decrease somewhat to adjust to the available supply, since they are higher than in other comparable savanna areas of Africa (5).
2.1.4 Areas and growing stock at end 1985
The indications given in the above sections will result in the following tentative estimates of area and growing stock at end 1985.
Areas of natural woody vegetation estimated at end 1985
(in thousand ha)
Growing stock estimated at end 1985
(in million m3)
It is assumed that the planting rate will double in the next 5-year period in an attempt to fulfill the needs of an increasing population, particularly for household consumption. Although this doubling remains far below the recommended targets (3) (7), it is estimated that it may be difficult to exceed it, given the financial constraints and the very limited technical staff available.
Areas of established plantations estimated at end 1985
(in thousand ha)
|Age class||0–5||5–10||11–15||16–20||21–30||31–40||> 40|
|PHL 1||Various species (see table in section 1.2.2)||0.1||0.05||0.05||0.05||0.05||ε||0.3|
|PHH 1||Gmelina arborea||0.6||0.3||0.2||0.15||0.45||ε||1.7|
|P=P..1=PH.1||Total (industrial hardwood) plantations||0.7||0.35||0.25||0.2||0.5||ε||2.0|
Gmelina arborea should remain the main species planted, given its success and the many possible uses of its wood. Fuelwood plantations at the village level may develop also during this period.
Anonymous 1962 “Progress Report Gambia” - presented at British Commonwealth Forestry Conference, 1962 - Banjul
Anonymous 1965 “The Gambia - National Report on Forestry and Forest Industries Development” - Report presented at the Intergovernmental Conference on Timber Trends and Projects in Africa, 1965 - Banjul
Openshaw, K. 1973 “The Gambia: a Wood Consumption Survey and Timber Trend Study, 1973–2000” - Report to the ODA/LRD Gambia Land Resources Development Project - Midlothian (U.K.)
Department of Agriculture 1975 “The Gambia: Land and Vegetation Degradation Survey: The Need for Land Reclamation by Comprehensive Ecological Methods” - Banjul
Dunsmore, J.R. et al. 1976 “The Agricultural Development of The Gambia: an Agricultural, Environmental and Socioeconomic Analysis” - Land Resources Study 22 - Land Resources Division - Surbiton (U.K.)
Coordinator's office - Rural Development Project 1978 “Rural Development Programme 1980–1985 - Preparation Working Paper No. 4 - Forestry Development” - Banjul
Huygen, J.P. 1978 “Development of the Gambian River Basin - A forestry Study of the Basin”
Johnson, M.S. 1978 “Inventory of Mangroves Above the Proposed Gambia River Barrage at Yelitenda - The Gambia” - Project Report 54 - Land Resources Development Centre - Surbiton (U.K.)
Mc Ewan, R.J. 1978 “Afforestation Techniques for the Establishment of Gmelina arborea Linn. in the Western Division of The Gambia” - Banjul
FAO 1979 “Travel Report - The Gambia” - by R. Levingston - Rome
Ghana lies almost in the centre of those countries whose shores front along the Gulf of Guinea on the west coast of Africa. The coastline stretches over 565 km. The country covers in straight line some 675 km from south to north and 540 km from east to west and has a total area of 238 538 km2. Extreme longitudes are 3°07'W and 1°14'E and extreme latitudes 4°45'N and 11°11'N.
The country is generally undulating but the Akwapim, Kwahu, Mampong, Ejura and Gambaga scarps are prominent, although of no great height, and seldom exceeding 600 metres. The greatest altitude, 880 metres, is in the Volta region where a series of hill ranges runs in a northeast-south-west direction. These ranges continue north-eastwards into the Republic of Togo". The Volta is the most important river and others like the Pra, Ankobra and Tano run southerly to the sea and are navigable for about 80 km. The drainage is dominated by this system, which includes a vast artificial lake of over 770 000 ha. Soils are variable and in general moderately fertile and capable of supporting good growth, unless they remain bare for some years (7).
In the southern part of the country there are two rainy seasons (April–July and September–November). Rainfall is highest in the southwest, ranging from 1 250 to 2 150 mm.
The southeast has also two rainy seasons but a lower annual rainfall (750 mm). In the northern part, rainfall ranges between 1 100 and 1 250 mm and occurs in a single season (April–September) followed by a long dry season. The mean annual temperatures in Ghana average between 26 and 29°C. The climate is also influenced by the “harmattan” which blows south from the Sahara between December and February and produces a significant drop in humidity.
The present population of Ghana is about 11 446 000 inhabitants with an annual growth rate for the period 1975–1980 of 2.96%. According to the FAO Production Yearbook 1978 (Vol. 32), around half of the economically active population works in the agricultural sector, living in rural settlements with less than 5 000 inhabitants. Cultivation of cocoa, the main export crop, is restricted to the moist tropical forest zone. Cultivation of other commercial crops, such as copra, oil palm and citrus and of the staple foods (maize, plantain, cassava, yams and millet) is largely carried out by individual farmers, in most cases at subsistance level.
1. Present situation
1.1 Natural woody vegetation
The natural vegetation is tropical high forest in the southwest and savanna woodland north of this zone, where the climate is drier, petering out to savanna grasslands in the northern third as well as in the east. Near the coast are areas of scrub and grassland, with mangrove vegetation around the lagoons.
1.1.1 Description of vegetation types
The following description of the vegetation types, presented in the broad categories used in this study, is derived from (1) with minor adaptions based on (3).
Closed broadleaved forests (NHC)
The closed high forest lies within the “two-peak” rainfall belt (May–June and September–October). It has a storeyed structure. The ground flora is usually sparse and the shrub layer is not dense. Grasses are mostly absent. There is a closed lower canopy in which the trees have heavy crowns and low branches. They do not reach a height much greater than 18 m. The upper canopy is closed about 40 m high and is made of trees with tall straight stems, many of them with a small crown. Lastly, there are the emergents, which may reach up to 60 m of height, and do not form a closed canopy. Entwined through the entire system are lianes, some of which going right up into the crowns of the highest trees. The high forest has been divided into two types, the rainforest and the moist semi-deciduous forest. From the purely physiognomic point of view, the two types are rather similar and they differ mostly by their floristic composition.
- Within both types, the freshwater swamp communities are found mostly along the streams and contain a special flora. They are not rich in tree species nor in total number of trees. The main tree species are Alstonia boonei, Berlinia spp., Carapa procera, Mitragyna cïliata, Macrolobium spp. and Uapaca spp. Raphia palms and the climbing palms Ancistrophyllum and Calamus are very characteristic.
- The rainforest is situated in the most southwestern part of the country, where rainfall is highest, between 1 800 and 3 000 mm annually, and relative humidity is very high, close to saturation point. The harmattan has no real effect here and there is no month without rain. The country is generally low lying, but contains numerous small steep hills, with freshwater swamps in the valleys. The rainforest is characterized by the Cynometra ananta - Lophira procera - Tarrietia utilis association, and by the complete absence of Celtis spp. and Triplochiton scleroxylon. The three characteristic species are not deciduous, nor are the species of the lower canopy, such as Cola chlamydantha, Diospyros spp. Pentadesma butyracea, Protomegabaria stapfiana and Strombosia pustulata. Typical shrubs are Bertiera racemosa, Conopharyngia chippii and Randia hispida. Devastation of the forest has been caused by the gold and manganese mines through repeated cutting for timber, poles and fire-wood. Large areas around the mines now support a scrub vegetation where Alchornea cordifolia, Anthocleista sp. and Harungana sp. predominate, and trees of any size can hardly be found. The soil fertility in these areas has deteriorated considerably. Cocoa plantations are very few in this part of the country.
- The region, covered by moist semi-deciduous forest is generally at elevations higher than 150 m above sea level. The Kwahu, Mampong and Ejura Scarps, and the hills of Western Ashanti are prominent topographic features. The annual rainfall varies between 1 250 and 1 750 mm, although the upper limit may be exceeded in some of the higher altitude areas. Many of the species in the upper and emergent canopies are deciduous for variable periods between October and April. The characteristic species of the lower canopy are evergreen and mixed with the young trees of most of the species belonging to the dominant storeys. Under this canopy humidity prevails although other conditions exist along the northern limits of this type during the short harmattan period. This type of forest is actually more luxuriant than the rainforest and contains more useful timber species. Three associations are recognized:
the Lophira procera - Triplochiton scleroxylon association occurs to the immediate north and east of the rainforest, and is really a transition zone between the latter and the moist semi-deciduous type. Celtis spp. and Triplochiton scleroxylon are found in mixture with Cynometra ananta and Lophira procera. Just as the former species decrease towards the south, so do Cynometra and Lophira become scarce towards the north. Meliaceae such as Entandrophragma angolense, E. cylindricum, Guarea cedrata, Khaya ivorensis and Lovoa klaineana, and Leguminosae like Daniellia similis, Distemonanthus benthamianus, Parkia bicolor and Piptadeniastrum africanum are also well represented. Among the Sterculiaceae, Tarrietia utilis is rare, but Cola cordifolia, Pterygota macrocarpa and Sterculia rhinopetala begin to appear. The understorey species are those of the rainforest, except that Diospyros spp. becomes scarce. Where farming has taken place on the margins of this forest, the resulting secondary forest evolves towards the type described hereafter by the disappearance of Cynometra, Lophira and Tarrieta.
the Celtis spp. - Triplochiton scleroxylon association occupies the remainder of the tropical high forest area south of the line of the Kwahu and Mampong Scarps and its continuation to the northwest, except for a strip on the southeast. Celtis adolfi-frederici, C. sayauxii, C. kenkeri, Triplochiton scleroxylon, Cylicodiscus gabunensis, Piptadeni astrum africanum, Cola cordifolia, Pterygota macrocarpa, Sterculia elegantiflora, S. rhinopetala and S. tragacantha are common, while Lovoa klaineana and Parkia bicolor become scarce. Entandrophragma utile, Khaya anthotheca, Cistanthera papaverifera and Mansonia altissima make their appearance, particularly towards the north. Common understorey species are:
Corynanthe pachyceras, Lecaniodiscus cupanioides, Monodora myristica and Myrianthus spp. Among the shrubs, Mussaenda erythrophylla replaces M. chipii. Large areas have been and are being farmed for cocoa and foodcrops. Where a secondary forest has grown up, the light demanding species Albizia gummifera, A. zygia, Funtumia elastica, Pyonanthus angolensis, Terminalia ivorensis, T. superba and Triplochiton scleroxylon are present as well as those species usually not felled by the farmers, such as Amphimas pterocarpoides, Bombax buonopozense Ceiba pentandra, Chlorophora excelsa and Piptadenia africana. Near the towns and villages repeated farming has reduced the vegetation to shrub, with an occasional big tree as a relic of the former forest. Many of the cocoa farm maintain a skeleton structure of the forest to preserve the type of environment required by the cocoa crop.
Antiaris africana - Chlorophora excelsa association occupies the northern limit of the tropical high forest, a strip on the southeast adjoining the coastal scrub and grassland, and an area east of the Volta lake and continuing in Togo. The question of water availability becomes important here, for this vegetation type is more exposed to the drying effects of the harmattan than the forests to the south. Celtis and Triplochiton are still common, but to a lesser degree than in the former association. Antiaris africana, Chlorophora excelsa, Morus mesozygia, Nesogordonia papaverifera, Cola cordifolia, Mansonia altissima Pterygota macrocarpa and Sterculia spp. are well represented, as are Aningueria sp. and Chrysophyllum sp. Khaya grandifolia, and, to a lesser extent, K. anthotheca, replace K. ivorensis. In addition to the understorey species found in the Celtis - Triplochiton association, Chidlowia sanguinea and Talbotiella gentii are found in the north. This forest is slightly different in structure from the other types, for there is no significant differentiation between the emergent and upper canopies. The upper storey is uneven and broken. On account of the fires made for hunting and farming, the “derived woodland savanna” has encroached a great deal into this association.
- In the southern part, riverain forest is found. A similar type exists as outliers, usually on higher grounds with good drainage. In the upper canopy are Afzelia africana, Albizia gummifera, Antiaris africana, Bombax buonopo ense, Ceiba pentandra, Chlorophora excelsa, Cola cordifolia, Erythrophleum guineense, Terminalia superba and Triplochiton scleroxylon. The lower canopy contains Caloncoba dusenii, Celtis scotellioides, Monodora myristica, Napoleana parviflora, Teclea grandifoliola and Trichilia prieuriana, Mallotus oppositifolius and Mussaenda elegans occur among the shrubs.
- The strand and mangrove zone covers a narrow strip along the coast, tidal river estuaries and lagoons and is broken in places by the topography. The mangrove swamps are very restricted in area and distribution and rarely develop beyond a thicket stage. Laguncularia racemosa and Rhizophora racemosa are found on the seaward side of lagoons in saline conditions. Avicennia nitida occurs on the landward side of the swamps. The latter are in some places exploited for the bark, which is used for tanning fishing nets and, in other places, firewood is extracted for local use.
Open broadleaved forests (NHc/NHO)
The savannas occupy the northern two-thirds of the country. Large tracts of the southern parts are almost uninhabited. The population increases rapidly towards the north and the land becomes much more exploited for agriculture.
- The Guinea savanna woodland extends over the area north of the closed forest and reaches the southeast of the country. This woodland is typically composed of short statured trees, usually not forming a closed canopy and often very widely spaced. The ground flora is composed of a more or less continuous layer of grass. Some of the grass species attain a height of about 3.5 m. Most of the area lies within the “one peak” rainfall zone (August–September). Although annual precipitation is seldom less than 1 000 mm and may reach 1 250 mm, it is the intense dry season which is the limiting factor on the vegetation. The true Guinea savanna woodland is a climatic climax. Though this is the case in the centre and north of this zone, there is a very large area in the south (southern extremities of the northern region, north Ashanti, the African plains and the eastern Volta region) where this type of savanna woodland is considered to be a “derived savanna” brought about by human interference. Periodic grass fires - in many localities these are annual - sweep across the country during January to April. They are mainly caused for hunting. Many of the trees are fire resistant and have thick bark.
- Riverain woodland along the rivers in the northern area contains Anogeissus schimperi, Celtis integrifolia, Cola laurifolia, Cynometra vogelii, Lannea spp. and Parinari polyandra. Throughout the Guinea savanna woodland are Anogeissus schimperi, Butyrospermum parkii, Detarium senegalense and Parkia filicoidea. Daniellia oliveri is common in the south, and particularly so in the derived woodland savanna, where it is often associated with Entada sudanica. The Acacia are more frequent in the north. Combretum spp. and Terminalia spp. are numerous and often indicate areas of poor drainage. The savanna mahogany, Khaya senegalensis, is riparian. On worked out land, the vegetation consists of a short shrub growth of Bauhinia rufescens, Combretum spp. and Piliostigma thonningii (woodland fallow or NHc/NHOa). Fires and grazing tend to keep down its height.
- The Sudan savanna woodland is restricted to a small area in the extreme northeast of the country. It has the highest density of rural population which has resulted in settled farming. This zone has a very sparse tree cover. The arable land contains a sprinking of Butyrospermum parkii, Parkia filicoidea and Tamarindus indica, all of which provide an extra source of food for the local population.
Scrub formations (nH)
The coastal thicket and grassland zone extends from Takoradi eastwards along the coast (except where the strand and mangrove zone lies) in a belt widening inland until the lower west bank of the river Volta is reached. It coincides with an area of low rainfall (annual average of about 850 mm). In the west, from Sekondi to Winneba, the vegetation is predominantly dense thicket, 3.5 to 6 m high with taller scattered trees of Antiaris africana and Sterculia tragacantha. Small patches of grass savanna occur. Shrubs and small trees are Baphia nitida, Dichapetalum flexuosum and Hymenostegia afzelii. This thicket does yield firewood, though in small sizes, for the local population.
Behind Winneba the extent of the grassland increases and from Accra to the Volta the vegetation is predominantly grassland with small clumps of scrub, in certain areas strictly restricted to termite mounds. The characteristic tree of the Accra plains is Elaeophorhia drupifera; shrubs are Abutilon spp., Allophyllus warneckei, Cassia mimosoides, Fluggea virosa and Grewia carpinifolia. Irrigated farming is relatively widespread in this belt.
On the sandy foreshore, above high water mark and in succession of the grasses away from the sea, come such shrubs as Baphia nitida, Grewia spp. and Triumfetta rhomboidea.
1.1.2 Present situation of the woody vegetation
Areas of natural woody vegetation estimated at end 1980
(in thousand ha)
|154||1 167||1 321||397||1 718||6 500||1 575||5 400||6 975||2 680||300|
In the tropical high forest it is estimated that some 1 167 000 ha are intensively managed under the selection system, the exploitation being regulated on the basis of an annual allowable cut equal to the annual yield. The 154 000 ha of productive not intensively managed natural forest (NHCf1uc) are earmarked for conversion into other land uses. However, exploitation is controlled in some ‘protected timber lands’.
Areas of closed forests unproductive for terrain and stand conditions are practically negligible (NHCf2i = ε); only the mangrove represents a noteworthy area.
397 000 ha have been legally demarcated as protection reserves for reasons mainly of watershed management and soil conservation (NHCf2r).
It is considered that nowadays no virgin forest remains (NHCf1uv = 0).
The area classified as fallow forest (NHCa) contains also cocoa farms, bush fallows and foodcrop farms (8) (18). The total “forest area” occupied by shifting cultivation at the end of 1980 is estimated at 9 180 000 ha (17), about 6 500 000 ha laying in the high tropical forest zone, and the remaining 2 680 000 ha being located mostly in the derived woodland savanna.
The coastal thicket vegetation forms the ‘scrub’ zone (nH) along the coast of the country, expanding considerably towards the southeast.
52 000 ha of productive forest reserves in the savanna zone (10) and one fourth of the woodland savanna vegetation type are estimated representing productive open broadleaved forests (NHc/NHO1), the other three fourths being unproductive woodlands (NHc/NHO2), because of the scarcity of the tree cover and in some cases because of their legal status (approximately 850 000 ha of woodlands are estimated to be included in the Mole, Digya, Bui National Parks and in the Gbele Camme Production Reserve).
Savanna grasslands, areas under permanent pasture or crops, and the Sudan savanna, the latter characterized by a very dense population and a very intensive agricultural activity, have no sufficient woody cover and their areas are therefore excluded from the table.
The system of land tenure may be generally described as usufructuary. All forest lands are owned by traditional rural communities, whose titular heads are local chiefs. The lands are held in trust by the state for the latter (17) (18).
Legal status and management
The necessity of reservation of forest lands for protective purposes and for ensuring the future timber supplies of the country was recognized very early and proposals for a Forestry Bill existed already in the last century. It was not until 1927, however, that legal power to enforce reservation, without prejudicing the ownership of the land, was secured. From that date on a consistent policy of selection, demarcation and reservation has been pursued. The permanent forest estate, selected and demarcated, covered at the end of 1978 3 267 250 ha (18). The majority of the reserves, ranging in individual area from about 2 500 ha to 50 000 ha, are also fully settled and constituted. Constitution may include the right to cultivate permanent crops, mainly cocoa and coffee - such farms are demarcated -, local customary rights of hunting, access and collection of minor forest produce, poles and posts on permit and payment of fees, but the communities must forsake all rights to clear new farms. Timber exploitation concessions are granted by the Lands Commission after clearance by the Forestry Department.
The unreserved forests constitute lands destined to be alienated to agriculture. They still continue to contribute substantially to timber production. Government control exists in these areas that have been declared ‘protected timber lands’. Here concession holders are required to comply with the provisions of the forest service and to pay an additional royalty per area unit (13).
Five “national parks” exist, totalling an area of 10 357 km2. Only two of them, Bia and Nini-Suhien, are situated in the high tropical forest zone, and they cover 240 km2. The others lay in the woodland savanna. National parks are developed for tourism and its allied non-consumptive use, while at the same time guaranteeing the conservational integrity of the area. The country has also five ‘game production reserves’, occupying about 1 750 km2, two ‘wildlife sanctuaries’ covering 814 km2 and the ‘strict nature reserve’ of Kogyae (32 375 ha). Game production reserves are intended for consumptive use distinct from the non cunsumptive use of national parks (14) (18). The legal status of these parks and reserves does not permit timber exploitation. However, the Bia game production reserve is currently under controlled timber extraction and scientific research to find out the effect of logging and timber extraction on wild fauna (18).
Most production forest reserves have their management plans, which generally contain information on area, ownership and history, details of the growing stock, prescriptions on the silvicultural treatment to be effected, yields to be removed, and financial forecasts of revenue and expenditure. Preparatory work involves statistically designed enumeration surveys which give estimates of the growing stock within stipulated confidence limits and form the basis for yield prescriptions, and add also considerably to the knowledge on the occurrence and distribution of local flora.
Improvement thinnings, combined operations with assisted natural generation and regular stock surveys characterize the selection system as applied in the tropical high forest in Ghana. Management in the reserves with a low stocking and in the woodlands is by clear felling followed by artificial regeneration under the taungya system or by direct planting (3) (12).
Although the standard felling cycle in the natural forest is fixed at 25 years, it is important to mention that since the beginning of the seventies the former has been provisionally reduced to 15 years as to allow for the early salvaging of overmature trees before the advent of death and decay (8). The pre-exploitation works of enumeration, stock survey and climber cutting are however continued, with improvement thinnings being done as a post-exploitation operation. 35 000 ha were treated this way during the year 1978, and some 10 000 ha were or had been under natural regeneration (18). The Tropical Shelterwood System was experimentally tried out in the fifties, but abandoned in 1967 because the results did not justify the cost of the system (5).
Timber is extracted from the forest reserves and from salvage areas of unreserved forests in the respective proportions of 60 and 40% since 1970. Unreserved forests are a diminishing asset being progressively converted to other land uses (18).
Before granting timber rights over a piece of land, the Lands Commission seeks clearance from the Forestry Department with regards to the stocking of the area and whether its exploitation would be in the public interest or not. Exploitation of the concessions (area exceeding 800 ha, for minimum of five years and maximum of 25) and licences (area not exceeding 800 ha, for a maximum of 3 years) is controlled by the Forestry Department, while the Lands Commission, after having granted exploitation rights on behalf of the landowing chiefs, levies a concession rent per surface unit. Royalties for all sound trees felled and silvicultural fees are paid by the concessionaires or licencees according to legally fixed rates. At the end of 1977, 3 712 200 ha of reserved and 1 303 200 ha of unreserved areas (forest and woodlands) had been granted to various logging firms and individuals as timber concessions and licences (17).
Logging and transport are mainly activities of the private sector. They are carried out either by independent loggers producing for the open market as well as directly by wood industry firms. The use of power saws has developed considerably although felling by axe at piece rate is still practised by a number of timber producers, especially the small operators. The use of crawler tractors and wheel skidders has been generalized and logs are transported by road or rail. Any estimate of logging waste is arbitrary, as there has been no systematic study of this problem (17). Total log production in 1975 was 1 333 000 m3, with 440 000 m3 exported, 774 000 m3 delivered to local sawmills, 117 000 m3 used in the veneer and plywood industry and 1 700 m3 handsawn in the forest for local use (15). The FAO Yearbook of Forest Products estimates the production of sawlogs and veneer logs at 2 138 000 m3, of pitprops at 18 000 m3 and of railway sleepers at 65 000 m3, all for the year 1978. Thus, production has been increasing rapidly over the last few years. In 1977, there were 85 sawmills, mostly located in the high forest zone in the southwestern third of the country, 8 plywood plants, 1 veneer factory, and 2 parquet flooring industries. They are largely privately owned. The only chip-board factory was commissioned in 1976 and its annual output has averaged 22 400 m3. There are a number of furniture factories, a few of which are engaged in the production for export (17). It is important to note that the export of logs of the 14 most important commercial timbers is prohibited by law, in order to increase their local processing and to promote the introduction of lesser-known species in the export market.