Two types of degradation of the woody vegetation can be distingushed:
A qualitative degradation of closed forests related to logging and extraction of forest products (other than fuelwood). Logging of sawlogs and veneer logs is selective, with regard not only to species (selection of species accepted by the international market of which logging is profitable), but also to trees (selection of trees of good shape which can provide highly priced quality logs). This selection which has been going on for 30 years at a sustained pace will have most certainly a bearing on forest composition and value. Moreover, some species are disappearing and their seeds are difficult to collect (at least within a given country, as for instance Khaya ivorensis in Ivory Coast). In some cases, in savanna zones in particular, local populations may have a negative effect on woody vegetation by collecting particular products. This type of degradation is however, very unimportant compared to the one affecting savannas.
A degradation both qualitative and quantitative which is only noticeable in the savanna zone, resulting from the excessive population pressure. This process can therefore only worsen in the future. Various factors are at stake:
an important factor is the exploitation of fuelwood. It has been said in paragraph 1.1.3 that in many regions the volume of fuelwood collected was in excess of the annual wood productivity. A gradual degradation of woody vegetation results therefore, which in some cases can lead to a complete destruction;
the search for building material and in particular for poles for the construction of roofs, leads also to selective cutting in relation to size, species and locality. It is always within the most wooded areas that nice stems of the most termite-resistant species are extracted (Anogeissus leiocarpus, Hyphaene thebaica, Acacia scorpioides). Other species with slim and flexible stems are also particularly appreciated, such as Acacia seyal and A. raddiana;
consequences of grazing and over-grazing are also serious. Cattle is undeed another main factor in the destruction of vegetation associations. Plants most favoured are affected first, then the process is amplified if the carrying capacity of the grazing lands is exceeded, which is often the case. Substitution plants colonise empty spaces and jeopardize regeneration. Trampling also adds to the effects of overbrowsing. Furthermore, at the end of the dry season when the grass has disappeared, Mimoseae are appreciated as a fodder, shepherds climb up trees and prune or pollard them. Much time is needed before the mutilated trees can form a new crown. All Mimoseae species are threatened this way but in particular Faidherbia albida and Acacia scorpoioides, which leads to their gradual disappearance and results in reduction of tree density (tree density per ha can thus be divided by 4 or 5);
finally, bush fires which destroy regeneration can definitely inhibit the reconstitution of degraded woody cover and contribute also to the degradation by acting on the physiology of burnt trees. The degradation of the woody vegetation of mixed forest-grassland formations is therefore most serious.
Most critical areas are: subdesertic regions (Sahel, eastern horn of Africa), where populations are concentrated on grazing lands between wells and where vegetation goes on degrading and becoming more sparse; overpopulated savanna regions (Mossi region of central Upper Volta, peanut areas of western Senegal, Haoussa country of northern Nigeria, mining areas of Shaba (Zaire) and northern Zambia, lake Victoria belt; and lastly, mountainous areas with high population and little accessible wood resources: Abyssinian plateau (Ethiopia), Rwanda and Burundi. This quantitative degradation of mixed forest-grassland formations can only be stopped by management and protection measures. Many studies of plots protected for many years (Central African Rep., Chad, Ivory Coast, Guinea, Nigeria, Senegal, Tanzania) show the beneficial effect of protection measures against overexploitation by man, bush fires and grazing. This type of action is much less costly than plantation and its positive ecological effect is more beneficial than that obtained through massive plantations. However the above requires forestry institutions with sufficient staff and means. It also asks for a change in attitude by rural populations and wood traders.
Finally, a last type of degradation (even of destruction) must be mentioned: this is the one affecting Sahelian zones following the drought which has prevailed for more than ten years. When the rainy season is too short plants dry up more or less straight away and regeneration is lost. Furthermore, drought is responsible for an imbalance in the water supply of the trees and the oldest are eliminated as well as the sensitive species. Trees of Acacia tortilis, Commiphora africana and Sclerocarya birrea have been uprooted by wind after having dried up. Gum arabic trees (Acacia senegal) have also suffered quite a lot as well as Acacia nilotica.
2.1.3 Trends in forest utilization
In western Africa, export-oriented countries must be considered separately from those countries where production is aimed essentially at supplying domestic needs. Among the latter, two cases are possible:
forest allows for an increase of production which can be matched with growth of population and purchasing power and some diversification of uses (Ghana for instance, is considering replacing, whenever possible, imported raw materials by wood produced locally): this is the case of Guinea, Sierra Leone, Ghana and Nigeria (in this latter country production of plantations should contribute for a significant part to national production in 1985);
forests do not satisfy domestic needs: this is the case of Togo where the import of sawlogs and veneer logs should increase and of Benin where stagnation or even slight decrease of production is to be foreseen.
In the export-oriented countries severe decrease of forest resources will entail either a levelling off of production (as in Liberia where it should remain around 600 000 m3 of logs per year), or a decrease of production (as in Ivory Coast where it could be reduced to 2.5–3 million m3 per year around 1985). As a whole, despite probable diversification of used species, total annual production of western Africa should be around 7.5–8 million m3 of logs towards 1985, i.e. approximately 2 million m3 less than in 1978 (mostly because of Ivory Coast).
In central Africa trends should be different according to countries during the next five years. Cameroon and Congo should have their production increased. The growth should be more significant in Cameroon following the reconstruction of the Douala-Yaoundé road and the transfer of railway transportation capacity towards the eastern zones. In Congo, the end of the improvement work of the Brazzaville-Pointe Noire railway should allow for the setting-up of one or two new companies in the north. Production in Gabon should not increase much despite the installation of a new portion of the railway, because of depletion of okoumé stock in presently logged areas and the lack of prospects for species diversification. In Central African Rep. and Zaire there should not be significant changes from the present situation. In Equatorial Guinea a gradual resumption of logging is to be foreseen. In Angola, production from natural forests has been limited to 200 000 m3 per year. In the long run, insofar as infrastructure projects at present under study (deep water harbour south of Kribi, road east-west in southern Cameroon) are implemented, there should be a significant increase of production in Cameroon from the year 1990 to reach more than 7 million m3 around 2 010. It must be hoped, however, that development of southern and southeastern forest areas is carried out within the framework of a rational land-use plan in order to avoid a wastage of wood and water resources and a similar evolution as that of Ivory Coast. Logging of new forest areas should be preceded by forest inventories and studies related to land-use planning, forest harvesting regulations and forests of regeneration and reconstitution of logged-over forests. This approach is being used in the Congo where production should increase significantly towards the year 2 000. As for Zaire it is difficult at present to forecast development of forest logging; it should not, however, be spectacular within the next twenty years.
In eastern Africa the main characteristic will be the increasing share of plantations in forest production. In Kenya natural forests should provide a production limited to 100 000 m3, whereas plantations will produce more than 1 million m3 from 1985. In Tanzania production from natural forests go on decreasing (400 000 m3 in 1970, 150 000 m3 in 1980, and around 100 000 m3 in 1985) and plantations will substitute them. Zambia, Mozambique and Malawi will also produce wood from plantations. In those countries where timber plantations have not been established early enough, some shortage is to be expected; this is the case in Burundi, Rwanda and Uganda. Finally, some countries like Sudan, Ethiopia and Madagascar will be characterized by an improvement in forest logging and wood processing methods.
There should not be any noticeable change in the exploitation of fuelwood and other products in the next five years. However, in these areas where the present needs for wood outstrip forest productivity, the damaging effects of over-exploitation of woody vegetation can be expected to increase in severity. This effect can be better appraised by projecting to the year 2000. Total population of tropical Africa will have increased by 75%. The average needs per capita of fuelwood will not be reduced significantly either by substitution of other energy sources or by the improvement of household stoves. One can therefore assume a leveling off of consumption in rural areas and its slight decrease in urban centres, that is, as a whole, a reduction by 5% of average per capita consumption.
During the same period there will be a significant decrease of resources of natural woody vegetation due to clearing and degradation. If areas of forest plantations are projected to the year 2 000 using the same annual plantation rates as for 1981–85, there should be approximately, 2.5 to 3 million ha of plantations established between 1981 and 2000, equally distributed between industrial plantations and plantations aiming basically at satisfying local domestic needs (particularly fuelwood). However, these plantations will contribute very little to the satisfaction of fuelwood needs (see para. 2.2).
Using the same categories of countries already indicated in paragraph 1.1.2 for the study of the present fuelwood situation, it can be seen that the shortage will be generalized for countries of category 1 (subdesertic and sahelian countries). For countries of category 2 (densely populated savanna countries) there will be a decrease of more than 50% of present annual availability per capita and plantations will account for only approximately 3.5% of this availability. For countries of category 3 (savannas with low population density) annual availability per capita will decrease by 40%. This reduction will be higher than 70% for countries of category 4 (forest countries with a large population) due to the intensive clearing of natural vegetation and population growth. For category 5 (forest countries with a small population) availability will remain unchanged. As for category 6 (mountainous countries with large populations) there will be a levelling off of fuelwood availability despite population growth thanks to the reforestation activities.
In the year 2000 the balance should be as follows:
|Category||Needs m3/hab/year||Availability m3/hab/year||Balance m3/hab/year|
|2||1.1 to 1.6||0.45||- 0.55||to||- 1.15|
|3||1.1 to 1.6||1.51||- 0.1||to||+ 0.5|
|4||1.2 to 1.6||1.24||- 0.35||to||- 0.05|
|5||1.2 to 1.6||> 5||> 4|
|6||1.6 to 2||0.35||- 1.25||to||- 1.65|
Shortage in countries of category 1 will be worsened by destruction of the vegetation of grazing lands. Areas of shortage already identified in 1980 in countries of category 2 will extend over the surrounding zones (western Senegal, Gambia, Upper Volta, southern Benin and Togo, northern Nigeria). New areas will be lacking fuelwood: northern Cameroon, central Congo, western Zaire, central Angola, southern Mozambique, Erythrea. Rural population will be able to cope with this situation by harvesting wood beyond the productivity level of natural vegetation. The situation of urban populations (towns of more than 20 000 inhabitants) will worsen. This affects more than 80 million people. As for category 3 some areas (southern Mali, northern Benin, Togo, Ivory Coast and Ghana, southeastern Nigeria, eastern Upper Volta, southern Chad, northern Mozambique and southern Tanzania) will reach the present situation of category 2: rural populations will feel the need of overexploiting existing vegetation, and urban populations will be partly in a shortage situation. For countries of category 4, there will be a complete reversal of the situation. These areas will indeed find themselves in an apparent shortage situation in the year 2000. Rural populations will be very far from a shortage situation, because of the productivity of woody vegetation and the important forest fallow areas which have not been accounted for in these estimates. This apparent global shortage is derived from the critical situation of towns of Ivory Coast, Ghana, Nigeria and Liberia, affecting more than 30 million inhabitants. Finally, there should be no aggravation of the shortage situation prevailing in 1980 in countries of category 6, thanks to reforestation activities. Neither should there be any improvement, indicating that the area under plantations is not sufficient and that it is necessary to bring energy for households and cottage industry from other sources (local peat, imported commercial energies).
2.1.4 Areas at end 1985 (tables 7)
Tables 7a to 7d have been drawn up taking into account, on the one hand, estimate of cleared areas of the various forest types and, on the other hand, estimated transfers from one category to the other (areas of undisturbed forest being logged-over, areas of productive mixed tree formations - NHc/NHO1 - degraded into unproductive ones NHc/NHO2). These tables illustrate the likely situation of forest areas at the end of 1985. If the same deforestation and transfer rates are assumed up to the end of this century, the following areas are arrived at for the year 2000:
|Code||Forest types||Areas (in thousand ha)|
|NHCf1uv||Undisturbed productive closed broadleaved forests||101 000|
|NHCf1uc + NHCf1m||Logged-over productive closed broadleaved forests||35 600|
|NHCf1||Productive closed broadleaved forests||136 600|
|NHCf2||Unproductive closed broadleaved forests||51 350|
|NHCf||Closed broadleaved forests||188 950|
|NSf1uv||Undisturbed productive coniferous forests||150|
|NSf1uc + NS1m||Logged-over productive coniferous forests||300|
|NSf1||Productive coniferous forests||450|
|NSf2||Unproductive coniferous forests||500|
|NHBf||Bamboo forests||1 000|
|N.f||All closed forests||190 900|
|NHc/NHO1||Productive mixed tree formations||130 500|
|NHc/NHO2||Unproductive mixed tree formations||309 000|
|NHc/NHO||All mixed tree formations||439 500|
These forecasts for the year 2000 are very close to those made by FAO in 1979 (article by Lanly and Clement in Unasylva, vol. 31, No. 123), which were calculated (in thousand ha) at 187 080 for closed broadleaved forests and 188 790 for all closed forests together. There is, however, an important difference concerning areas of coniferous forest which had been estimated at 1.71 million ha: this latter estimate derives from an overestimation of areas in 1980 in the former FAO study stemming from the inclusion of mixed coniferous - broadleaved montane forests in the unproductive coniferous forests, whereas they have been grouped into the broadleaved forests in the present study.
TABLE 7a - Areas of natural woody vegetation estimated at end 1985
Closed broadleaved forests (NHC)
(in thousand ha)
|undisturbed NHCf1uv||logged NHCf1uc||NHCf1m||NHCf1||NHCf2||total||% (region)||NHCa|
|NORTHERN SAVANNA REGION||514||4||0||518||256||774||0.37||ε|
|Central African Republic||3010||430||3440||120||3560||1.71||330|
|EAST AFRICA AND MADAGASCAR||2570||8152||505||11227||10033||21260||10.28||6488|
|TROPICAL SOUTH AFRICA||0||0||0||0||0||0||0||0|
TABLE 7b - Areas of natural woody vegetation estimated at end 1985
Coniferous forests (NS)
(in thousand ha)
|EAST AFRICA AND MADAGASCAR||245||297||15||557||525||1082||100.00||20|
TABLE 7c - Areas of natural woody vegetation estimated at end 1985
Bamboo forests (NHB)
(in thousand ha)
|EAST AFRICA AND MADAGASCAR||ε||700||2||702||290||992||91.68||ε|
TABLE 7d - Areas of natural woody vegetation estimated at end 1985
Closed broadleaved, coniferous and bamboo forests (N.f)
(in thousand ha)
|NORTHERN SAVANNA REGION||514||4||0||518||256||774||0.37||0.18|
|Central African Republic||3010||430||3440||120||3560||1.70||5.72|
|EAST AFRICA AND MADAGASCAR||2815||9149||522||12486||10849||23335||11.16||2.66|
|TROPICAL SOUTH AFRICA||0||0||0||0||0||0||0||0|