2.1 Natural woody vegetation
2.1.1 Deforestation
Introduction
The impact of man on the natural vegetation of Africa is very old and very important as has been indicated in paragraph 1.1.1. This influence, however, has greatly increased in the last twenty years because of population growth and economic development. It is important to distinguish between closed forest and open formations since deforestation processes and effects are quite different.
a) Closed forests
The traditional practice of shifting cultivation had until the start of the century only a qualitative effect on closed forests since low population density and subsistence economy did not affect the forest areas which regenerated naturally after cropping in the form of forest fallow and secondary forests: fallow periods were long and allowed for a regrowth of the forest. Population migrations were quite limited for lack of means to penetrate forest areas. A large part of the population was concentrated, by their own choice or by decision of the colonial administration, along the few existing roads (as is still the case in Gabon). For the last forty years, and more particularly for the last twenty years, population growth and development of forest logging infrastructure have combined their effects and have been jointly responsible in many countries, of western Africa particularly, for the clearing of large forest areas. The various steps of this deforestation are the following: opening of logging roads, rush of alien populations using these roads to penetrate the forest, each family settling a few hundred metres from their neighbour in order to secure the largest extension possible from the first clearing. The end result is a gradual denuding of forest areas, in which the many clearings become larger and larger and merge after a few years. It is therefore very difficult to correctly estimate the areas actually cleared every year and, in many cases (e.g. Ivory Coast), estimates have been based mainly on the size of forest patches and their transfers from one size class to another (i.e. patches of more than 500 ha, patches of 100 to 500 ha, patches of 10 to 100 ha and mosaics forest-clearings with patches of less than 10 ha). This method has generally led to an overestimation of forest areas “cleared” annually. This is why it is necessary to check these figures with estimates of agricultural areas, on condition that this assessment of forest fallow areas in tropical Africa remains approximate. The word “clearing” should have been replaced by that of “piecemeal destruction”. The terms used to indicate mosaics of forest and clearings, where forests are reduced to relics or patches of small size, are also sometimes misleading as people speak of “degraded forest” or “cultivated forest”, two terms which lack precision. Geographers and surveyors, especially, often confuse the natural low forests or those with an open canopy, with areas which have been subject to degradation by man, and this often brings some uncertainty in the map legends, particularly those of topographic maps.
All African countries with closed forests are not affected to the same extent by clearing for agriculture. In particular in the low population density countries of central Africa (Central African Rep., Congo, Gabon and Equatorial Guinea) agricultural clearing does not account in total for more than 45 000 ha of deforestation per year, that is less than 0.1% of their total area of closed forest. On the contrary Ivory Coast and Nigeria with annual forest clearing rates of 310 000 and 285 000 ha respectively during the last five years, i.e. about 10% of their area of productive closed forest, are in a serious situation, since deforestation has gone on for twenty-five years at an accelerated pace (more than 70% of the forest area which Ivory Coast had at the beginning of the century has already been cleared). Other countries or parts of countries are in a state which tends to be equally serious: Madagascar, southeastern Guinea, southwestern Cameroon and lower Zaire.
As a whole the closed forest areas which have disappeared annually during the last five years can be estimated at 1.33 million ha, i.e. 0.61% of the total closed forest area in 1980. This rate tends to decrease slightly in western Africa (with the exception of Nigeria) and eastern Africa for the simple reason that few large forest areas remain and because of the forest protection regulations adopted. It is increasing lightly in central Africa especially in Zaire and Angola.
The consequences of tropical forest clearing are most severe. Not only are they responsible for the wastage of an enormous amount of woody material with a significant proportion of quality logs (i.e. annual loss of 50 to 100 million m3, that is 3 to 6 times the annual production of sawlogs and veneer logs) but also they may cause irreversible ecological damage when they are practised on large areas as is the case in western Africa, lower Zaire and Madagascar. It is difficult to appraise and quantify the actual consequences of deforestation. They can be assessed restrictively by limiting the study to the area cleared itself: even in this case the impact is already considerable as there is a total change of ecosystem (microclimate, soil, vegetation, bacterian flora, animals) but it is relatively easy to analyse. One of the most serious consequences related to forest clearing is the loss of genetic plasma and of the seed bearers which leads to the complete disappearance of many species. On the contrary the impact of deforestation on the neighbouring zones is much more complex to assess: changes in water regimes, erosion, climatic modifications, spreading of diseases, diffusion of polluting agents, change of carbon dioxide content of the atmosphere.
The situation of closed forest of tropical Africa is alarming only in the countries of the Atlantic coast and in Burundi and Rwanda; it is most serious in Madagascar. These facts are generally well known now and taken into consideration by the authorities concerned in the form of certain decisions. Forest cover monitoring is essential since it allows for the correct estimation of the deforestation processes and for the forecasting of their impact on the environment, at least in a broad way. Three African countries (Togo, Benin and Cameroon) have thus carried out, with the assistance of FAO and UNEP, a pilot project on tropical forest cover monitoring, which allowed for the reassessment of their forest areas and of the changes in vegetation cover in some critical areas.
The issue of the stability of the limits between moist forests and savannas is also worth mentioning. Because of their moisture, tropical closed forests are not affected by fires which, at most, can penetrate the undergrowth of the fringes and may contribute to the disappearance of forest patches within the savannas (such as in upper Guinea, Ivory Coast and Madagascar). It appears therefore, that it is mainly through the successive action of man and fires, that deforestation is followed by the spreading of savanna. Many forest patches within savannas beyond the forest limit in western Africa (in Fouta Djalon, in central and lower Guinea, in Ivory Coast, in Togo and in Benin) bear witness to the larger extension of moist forest of that region in the past: during its phase of maximum extension it could have reached latitude 10° N and form a continuous block with the Cameroon-Congolese forest zone. At present the forest-savanna contact is often clearcut and sharp, with few examples of transitional zones. However, there are some examples of natural reforestation of savannas in Gabon, Cameroon, Congo, Zaire and Ivory Coast.
The limit of the closed forest appears therefore fairly stable and corresponds to a balance between derived savannas maintained by fires and the forests capable of regeneration in the present conditions.
b) Mixed forest-grassland tree formations
Intense human impact in the past, as observed in practically all countries, has resulted in an almost complete disappearance of climax forest formations leading to a reduction of the woody component, viz. to a considerable expansion of mixed forest-grassland formations with a more and more reduced tree cover. This destructive action is going on under the combined action of man, cattle and fire (see paragraph 1.1.1). The new aspect is that, in some cases, because of its expansion and cumulative effect, this degradation is now leading to an almost complete disappearance of the woody cover to a level of less than 10%. The corresponding formation cannot be described any longer as a woody vegetation type. Considerable growth of population in the savanna zones is another factor responsible for the worsening of deforestation. In addition, some important hydroelectric and irrigation projects take their toll on the mixed forest-grassland tree formations. The annual rate of clearing of these formations has been estimated at 2.35 million ha. This estimate is still approximative as few precise data are available on this issue. In many cases the deforestation estimates at national level are derived from the multiplication of annual rates of clearing per agricultural family by the total number of families, in relation with the main crops established. The highest rates of clearing are in Ivory Coast, Nigeria, Zaire, Sudan and other east African countries (Ethiopia, Malawi, Mozambiqque, Tanzania). The decrease of areas of productive formations (NHc/NHO1) may correspond either to complete clearing or to transfers to unproductive formations (NHc/NHO2). In most cases these transfers cannot be figured out with precision.
The destruction of the woody component of open formations has direct effects on cleared areas. The impact of fires becomes more important. The fire tolerant pioneer vegetation isoften not palatable to animals (leathery leaves, thorns), soils are sterilized, hard pans are formed, watersheds dry up, no woody regeneration occurs and the process leads gradually to a more or less complete desertification or at least a “biological sterilization” of the environment. Finally, and this is the most serious, local populations suffer as they cannot find any resources for fuelwood and house construction (see para. 2.1.3), while animals have less and less fodder at their disposal.
The situation of subdesertic countries (Sahel in western Africa, eastern horn of Africa and southeastern part of the continent) is particularly serious from this point of view. Vegetation monitoring in these countries should be rapidly started, using remote sensing techniques which are more easily applicable than in closed forest areas since there is no cloud cover during most of the year. This monitoring will be useful to avoid reaching irreversible thresholds of deforestation and degradation of woody vegetation.
Comments on deforestation tables (tables 6)
Below are some comments on tables 6a to 6d which include estimated of closed forest areas (N.f) cleared annually during 1976–80 and 1981–85.
The areas of closed broadleaved forest cleared annually in tropical Africa during the last five years (1976–80) is around 1.32 million ha, of which 700 000 ha (e.g. 55%) are deforested in western Africa, especially in Ivory Coast (310 000 ha) and Nigeria (285 000 ha). For these two countries the situation is serious. Clearing for agriculture during the last twenty years has significantly jeopartized the future of forestry in these countries and wasted a considerable potential wealth, much higher than that of the logs extracted before clearing. Annual rates of clearing of closed broadleaved forests and of productive closed broadleaved forests are 4.0 and 5.0% respectively for the whole of western Africa. In the case of Nigeria, and even more for Ivory Coast, a significant decrease of forest production can be foreseen from now to 1985. The situation is less alarming for the time being, for Liberia, Guinea, and especially Ghana, countries in which annual deforestation rates are not more than a few tens of thousands of ha.
In central Africa the situation is not serious. Only Zaire - the annual deforestation rate of which has been estimated at 165 000 ha for 1976–80 and is likely to increase (180 000 ha annually projected for the period 1981–85) - and Cameroon (80 000 ha/year) have annually deforested areas which are significant in absolute terms. As a whole, however, the Cameroon-Congolese block is reduced by 350 000 ha/year, that is 0.2% of the total area and 0.25% of productive forest areas.
TABLE 6a - Average annual deforestation
Closed broadleaved forests (NHC)
(in thousand ha)
| Country | Productive | Unproductive | All | ||||||||||||||||||
| undisturbed NHCf1uv | logged NHCf1uc | total NHCf1 | NHCf2 | NHCf | |||||||||||||||||
| 1976–80 | 1981–85 | 1976–80 | 1981–85 | 1976–80 | 1981–85 | 1976–80 | 1981–85 | 1976–80 | 1981–85 | ||||||||||||
| Chad | |||||||||||||||||||||
| Gambia | 0.2 | 0.2 | 0.2 | 0.2 | 0.5 | 2 | 0.7 | 2.2 | |||||||||||||
| Mali | |||||||||||||||||||||
| Niger | |||||||||||||||||||||
| Senegal | ε | ε | ε | ε | ε | ε | ε | ε | |||||||||||||
| Upper Volta | |||||||||||||||||||||
| NORTHERN SAVANNA REGION | ε | ε | ε | ε | ε | ε | 1 | 2 | 1 | 2 | |||||||||||
| Benin | 0.3 | 0.2 | 1.2 | 1 | 1.5 | 1.2 | 1.5 | 1.2 | |||||||||||||
| Ghana | 27 | 22 | 27 | 22 | 27 | 22 | |||||||||||||||
| Guinea | 15 | 15 | 15 | 15 | 30 | 30 | 6 | 6 | 36 | 36 | |||||||||||
| Guinea-Bissau | 4 | 5 | 8 | 9 | 12 | 14 | 3 | 3 | 15 | 17 | |||||||||||
| Ivory Coast | ε | ε | 310 | 290 | 310 | 290 | ε | ε | 310 | 290 | |||||||||||
| Liberia | ε | ε | 39 | 44 | 39 | 44 | 2 | 2 | 41 | 46 | |||||||||||
| Nigeria | ε | ε | 265 | 280 | 265 | 280 | 20 | 20 | 285 | 300 | |||||||||||
| Sierra Leone | 4.4 | 3 | 4.4 | 3 | 1.4 | 3 | 5.8 | 6 | |||||||||||||
| Togo | 0.5 | 0.5 | 1.2 | 1.3 | 1.7 | 1.8 | 0.3 | 0.3 | 2 | 2.1 | |||||||||||
| WEST AFRICA | 20 | 21 | 671 | 665 | 691 | 686 | 33 | 34 | 724 | 720 | |||||||||||
| Angola | ε | ε | 40 | 44 | 40 | 44 | ε | ε | 40 | 44 | |||||||||||
| Cameroon | 3 | 3 | 75 | 75 | 78 | 78 | 2 | 2 | 80 | 80 | |||||||||||
| Central African Republic | 1 | 1 | 4 | 4 | 5 | 5 | 5 | 5 | |||||||||||||
| Congo | 1.5 | 1.5 | 20.5 | 20.5 | 22 | 22 | ε | ε | 22 | 22 | |||||||||||
| Equatorial Guinea | ε | ε | 2.5 | 3 | 2.5 | 3 | ε | ε | 2.5 | 3 | |||||||||||
| Gabon | ε | ε | 15 | 15 | 15 | 15 | 15 | 15 | |||||||||||||
| Zaire | 145 | 155 | 20 | 25 | 165 | 180 | ε | ε | 165 | 180 | |||||||||||
| CENTRAL AFRICA | 151 | 161 | 177 | 186 | 328 | 347 | 2 | 2 | 330 | 349 | |||||||||||
| Burundi | 0.2 | 0.2 | 0.2 | 0.2 | 0.2 | 0.2 | 0.4 | 0.4 | |||||||||||||
| Ethiopia | 2 | 1 | 5 | 5 | 7 | 6 | ε | ε | 7 | 6 | |||||||||||
| Kenya | 2 | 2 | 3 | 1 | 3 | 1 | 5 | 5 | 6 | 6 | 11 | 11 | |||||||||
| Madagascar | 40 | 35 | 120 | 110 | 160 | 145 | 5 | 5 | 165 | 150 | |||||||||||
| Malawi | ε | ε | ε | ε | ε | ε | |||||||||||||||
| Mozambique | ε | ε | 9 | 9 | 9 | 9 | 1 | 1 | 10 | 10 | |||||||||||
| Rwanda | ε | ε | 1.5 | 1.8 | 1.5 | 1.8 | 0.9 | 1 | 2.4 | 2.8 | |||||||||||
| Somalia | 1 | 1 | 1 | 1 | 2 | 2 | 3 | 3 | |||||||||||||
| Sudan | 5 | 4 | 5 | 4 | ε | ε | 5 | 4 | |||||||||||||
| Tanzania | ε | ε | 8 | 8 | 8 | 8 | 2 | 2 | 10 | 10 | |||||||||||
| Uganda | 10 | 2 | 10 | 2 | 10 | 10 | ε | ε | 10 | 10 | |||||||||||
| Zambia | 5 | 5 | 25 | 25 | 30 | 30 | 10 | 10 | 40 | 40 | |||||||||||
| Zimbabwe | ε | ε | ε | ε | ε | ε | ε | ε | |||||||||||||
| EAST AFRICA AND MADAGASCAR | 49 | 43 | 188 | 177 | 237 | 220 | 27 | 27 | 264 | 247 | |||||||||||
| TROPICAL SOUTH AFRICA | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |||||||||||
| TROPICAL AFRICA | 220 | 225 | 1036 | 1028 | 1256 | 1253 | 63 | 65 | 1319 | 1318 | |||||||||||
1 Of which 1(000) ha of managed forests (NHCf1m)
2 Of which 7(000) ha of managed forests (NHCf1m)
TABLE 6b - Average annual deforestation
Coniferous forests (NS)
(in thousand ha)
| Country | Productive | ||||||||||
| undisturbed NSf1uv | logged NSf1uc | total NSf1 | Unproductive NSf2 | All NSf | |||||||
| 1976–80 | 1981–85 | 1976–80 | 1981–85 | 1976–80 | 1981–85 | 1976–80 | 1981–85 | 1976–80 | 1981–85 | ||
| Ethiopia | 1 | ε | 2 | 2 | 3 | 2 | ε | ε | 3 | 2 | |
| Kenya | 1 | 1 | 21 | 21 | 3 | 3 | 2 | 2 | 5 | 5 | |
| Somalia | 0.5 | 0.5 | 0.5 | 0.5 | ε | ε | 0.5 | 0.5 | |||
| Sudan | ε | ε | ε | ε | ε | ε | |||||
| EAST AFRICA AND MADAGASCAR | 2 | 1 | 4 | 4 | 6 | 5 | 2 | 2 | 8 | 7 | |
| TROPICAL AFRICA | 2 | 1 | 4 | 4 | 6 | 5 | 2 | 2 | 8 | 7 | |
1 Of which 1(000) ha of managed forests (NSf1m)
TABLE 6c - Average annual deforestation
Bamboo forests (NHB)
(in thousand ha)
| Country | Productive | Unproductive | All | ||||||||
| undisturbed NHBf1uv | logged NHBf1uc | total NHBf1 | NHBf2 | NHBf | |||||||
| 1976–80 | 1981–85 | 1976–80 | 1981–85 | 1976–80 | 1981–85 | 1976–80 | 1981–85 | 1976–80 | 1981–85 | ||
| Zaire | 2 | 2 | 2 | 2 | |||||||
| CENTRAL AFRICA | 2 | 2 | 2 | 2 | |||||||
| Burundi | 0.3 | 0.3 | 0.3 | 0.3 | |||||||
| Ethiopia | |||||||||||
| Kenya | 3 | 3 | 3 | 3 | |||||||
| Rwanda | 0.4 | 0.4 | 0.4 | 0.4 | |||||||
| Uganda | |||||||||||
| EAST AFRICA AND MADAGASCAR | 4 | 4 | 4 | 4 | |||||||
| TROPICAL AFRICA | 6 | 6 | 6 | 6 | |||||||
TABLE 6d - Average annual deforestation
Closed broadleaved, coniferous and bamboo forests (N.f)
(in thousand ha)
| Country | Productive | Unproductive | All | ||||||||||||||||||
| undisturbed N.f1uv | logged N.f1uc | total N.f1 | N.f2 | N.f | |||||||||||||||||
| 1976–80 | 1981–85 | 1976–80 | 1981–85 | 1976–80 | 1981–85 | 1976–80 | 1981–85 | 1976–80 | 1981–85 | ||||||||||||
| Chad | |||||||||||||||||||||
| Gambia | 0.2 | 0.2 | 0.2 | 0.2 | 0.5 | 2 | 0.7 | 2.2 | |||||||||||||
| Mali | |||||||||||||||||||||
| Niger | |||||||||||||||||||||
| Senegal | ε | ε | ε | ε | ε | ε | ε | ε | |||||||||||||
| Upper Volta | |||||||||||||||||||||
| NORTHERN SAVANNA REGION | ε | ε | ε | ε | ε | ε | 1 | 2 | 1 | 2 | |||||||||||
| Benin | 0.3 | 0.2 | 1.2 | 1 | 1.5 | 1.2 | 1.5 | 1.2 | |||||||||||||
| Ghana | 27 | 22 | 27 | 22 | 27 | 22 | |||||||||||||||
| Guinea | 15 | 15 | 15 | 15 | 30 | 30 | 6 | 6 | 36 | 36 | |||||||||||
| Guinea-Bissau | 4 | 5 | 8 | 9 | 12 | 14 | 3 | 3 | 15 | 17 | |||||||||||
| Ivory Coast | ε | ε | 310 | 290 | 310 | 290 | ε | ε | 310 | 290 | |||||||||||
| Liberia | ε | ε | 39 | 44 | 39 | 44 | 2 | 2 | 41 | 46 | |||||||||||
| Nigeria | ε | ε | 265 | 280 | 265 | 280 | 20 | 20 | 285 | 300 | |||||||||||
| Sierra Leone | 4.4 | 3 | 4.4 | 3 | 1.4 | 3 | 5.8 | 6 | |||||||||||||
| Togo | 0.5 | 0.5 | 1.2 | 1.3 | 1.7 | 1.8 | 0.3 | 0.3 | 2 | 2.1 | |||||||||||
| WEST AFRICA | 20 | 21 | 671 | 665 | 691 | 686 | 33 | 34 | 724 | 720 | |||||||||||
| Angola | ε | ε | 40 | 44 | 40 | 44 | ε | ε | 40 | 44 | |||||||||||
| Cameroon | 3 | 3 | 75 | 75 | 78 | 78 | 2 | 2 | 80 | 80 | |||||||||||
| Central African Republic | 1 | 1 | 4 | 4 | 5 | 5 | 5 | 5 | |||||||||||||
| Congo | 1.5 | 1.5 | 20.5 | 20.5 | 22 | 22 | ε | ε | 22 | 22 | |||||||||||
| Equatorial Guinea | ε | ε | 2.5 | 3 | 2.5 | 3 | ε | ε | 2.5 | 3 | |||||||||||
| Gabon | ε | ε | 15 | 15 | 15 | 15 | 15 | 15 | |||||||||||||
| Zaire | 145 | 155 | 20 | 25 | 165 | 180 | 2 | 2 | 167 | 182 | |||||||||||
| CENTRAL AFRICA | 151 | 161 | 177 | 186 | 328 | 347 | 4 | 4 | 332 | 351 | |||||||||||
| Burundi | 0.2 | 0.2 | 0.2 | 0.2 | 0.5 | 0.5 | 0.7 | 0.7 | |||||||||||||
| Ethiopia | 3 | 1 | 7 | 7 | 10 | 8 | ε | ε | 10 | 8 | |||||||||||
| Kenya | 3 | 3 | 5 | 1 | 5 | 1 | 8 | 8 | 11 | 11 | 19 | 19 | |||||||||
| Madagascar | 40 | 35 | 120 | 110 | 160 | 145 | 5 | 5 | 165 | 150 | |||||||||||
| Malawi | ε | ε | ε | ε | ε | ε | |||||||||||||||
| Mozambique | ε | ε | 9 | 9 | 9 | 9 | 1 | 1 | 10 | 10 | |||||||||||
| Rwanda | ε | ε | 1.5 | 1.8 | 1.5 | 1.8 | 1.3 | 1.4 | 2.8 | 3.2 | |||||||||||
| Somalia | 1.5 | 1.5 | 1.5 | 1.5 | 2 | 2 | 3.5 | 3.5 | |||||||||||||
| Sudan | 5 | 4 | 5 | 4 | ε | ε | 5 | 4 | |||||||||||||
| Tanzania | ε | ε | 8 | 8 | 8 | 8 | 2 | 2 | 10 | 10 | |||||||||||
| Uganda | 10 | 2 | 10 | 2 | 10 | 10 | ε | ε | 10 | 10 | |||||||||||
| Zambia | 5 | 5 | 25 | 25 | 30 | 30 | 10 | 10 | 40 | 40 | |||||||||||
| Zimbabwe | ε | ε | ε | ε | ε | ε | ε | ε | |||||||||||||
| EAST AFRICA AND MADAGASCAR | 51 | 44 | 192 | 181 | 243 | 225 | 33 | 33 | 276 | 258 | |||||||||||
| TROPICAL SOUTH AFRICA | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |||||||||||
| TROPICAL AFRICA | 222 | 226 | 1040 | 1032 | 1262 | 1258 | 71 | 73 | 1333 | 1331 | |||||||||||
1 Of which 2(000) ha of managed forests (N.f1m)
2 Of which 7(000) ha of managed forests (N.f1m)
Annual deforestation in eastern Africa (with the exception of Madagascar) is less important (around 100 000 ha/year), but it corresponds to 0.81% of total forest area and 1.36% of productive forest areas. These rates are equal to 2.9% and 2.4% for the closed broadleaved forests for Burundi and Rwanda respectively, which have their last forest areas being gnawed away by farmers in search of new land.
Estimated areas of closed broadleaved forest cleared annually in Madagascar are important: 165 000 ha per year of which 160 000 ha of productive forests, that is an annual rate of 1.6% for all closed broadleaved forests and 2.4% for productive ones. A slight trend towards a decrease of the annual rate of clearing can be observed (reduction of about 10% of the rate for the period 1981–85 compared with 1976–80).
As a whole it can be said that clearing is not a threat in the medium term neither to the ecological balance nor to the economic resources of the Cameroon-Congolese block. On the contrary the coastal block of western Africa is under very severe attack and its gradual disappearance is already a fact. Every measures must be taken in Nigeria, Ivory Coast, Sierra Leone, Liberia and Guinea in order to constitute a core of permanent forests under management and control, in order to stop the process of total destruction of the productive forests. Such an observation is also valid for Madagascar.
Clearing of coniferous forest is not important in general (table 6b), although in Kenya the productive forests are being reduced annually by 1.4%.
Clearing of bamboo stands is difficult to estimate (table 6c) and has been estimated in total at 6 000 ha per year, that is an annual rate of decrease of around 0.6%.
In the long run there is a real ecological threat to the whole continent, and mankind in 1980 should be concerned about what will be left of the forest cover of Africa in the second half of the twenty-first century.
Clearing of mixed forest-grassland tree formations (NHc/NHO)
It is more difficult to estimate the decrease of mixed tree formations than that of closed forests. The deforestation rates as projected by this study for the period 1981–85 can be derived by comparing the areas in 1980 given in table 1e and the corresponding ones in 1985 of table 7e.
Annual clearing of mixed tree formations during 1981–85 is approximately 290 000 ha in the northern savanna region, with the following distribution: Chad 80 000 ha, Gambia 3 000 ha, Mali 40 000 ha, Niger 60 000 ha, Senegal 49 000 ha and Upper Volta 60 000 ha. Annual clearing is only 0.68% of total area (some 43 million ha in 1980), varying from 0.45% for Mali to 2% for Gambia. But it affects populated regions and is concentrating therefore on zones where natural vegetation is disappearing gradually, leading to serious consequences, both economic (reduction of resources of fuelwood and other industrial wood), and ecological (soil degradation and sterilization).
The annual rate of clearing of mixed tree formations in western Africa amounts to 535 000 ha with the following breakdown: Benin 65 000 ha, Ghana 50 000 ha, Guinea 50 000 ha, Guinea-Bissau 40 000 ha, Ivory Coast 220 000 ha, Nigeria 100 000 ha and Togo 10 000 ha. Areas cleared in Liberia and Sierra Leone are negligible. The same observation as for the northern savanna region can be made. The annual rate of clearing of mixed tree formations is 1.4%, reaching 4% in Ivory Coast: the present agricultural development of the latter country in its northern savanna region could lead to the same effect as those derived from the clearing of natural vegetation in its southern part. In Guinea-Bissau the present rate of deforestation is also very high (2.8%). In central Africa about 320 000 ha of mixed tree formations disappear every year, of which: 50 000 ha in Angola, 20 000 ha in Cameroon, 50 000 ha in Central African Rep. and approximately 190 000 ha in Zaire. The global annual rate of deforestation is small (0.2%). The huge areas of woodlands and wooded savannas in Central African Rep. and Angola are little affected, except locally. In Zaire although the average rate is small (0.26%) the amount of areas annually cleared in some parts of Kasai and Shaba must not be underrated.
It is estimated that 1.14 million ha of mixed tree formations are cleared annually in the whole region of eastern Africa and Madagascar, with the following breakdown: Kenya 20 000 ha, Madagascar 6 000 ha, Malawi 150 000 ha, Mozambique 110 000 ha, Rwanda 2 000 ha, Somalia 10 000 ha, Sudan 500 000 ha, Tanzania 120 000 ha, Uganda 40 000 ha, Zambia 30 000 ha and Zimbabwe 70 000 ha. The global annual rate of clearing is thus 0.6%. This clearing affects populated areas and is therefore locally detrimental. Sudan (1.05%), Uganda (0.75%), Mozambique (0.75%) and particularly Malawi (3.75%) are the countries most affected because of their important population concentrations. The situation is particularly serious in the latter country around lake Victoria, in the Copper Belt region of Zambia and in western Mozambique. Low rates in Burundi and Rwanda illustrate only the fact that almost all land suitable for agriculture has been deforested.
In southern tropical Africa annual decrease of mixed tree formation areas has been tentatively estimated at 30 000 ha in Botswana and 50 000 ha in Namibia. Clearing is limited to populated areas and represent only a very small percentage of existing areas.
For the whole of tropical Africa the area of mixed tree formations presently cleared annually is estimated at some 2.34 million ha, that is 0.5% of total area. This rate does not appear threatening in the medium term but must be carefully thought about in the long run. Ways of preserving and managing forest reserves in savannas and of settling and intensifying agriculture must be designed if disastrous economical and ecological consequences are to be avoided for a large number of African countries.
