BY THE STAFF OF THE DIVISION OF FORESTRY AND FOREST PRODUCTS
WITH the exception of North Africa, which is almost entirely within the Mediterranean vegetation zone, and the southern part of the Union of South Africa, Africa is a land of tropical forests.1
1 For articles on African forests which have appeared in Unasylva see "The Disappearance of the Tropical Forests of Africa," by A. M. A. Aubréville, Vol. I, No. 1, and "An Estimate of the Shrinkage of Africa's Tropical Forests," by II. L. Shantz, Vol. II, No. 2.
These forests are influenced either by a warm, humid climate with a short dry season or by a hot tropical climate with a long dry season. The types of tree association. - it is difficult to term them all "forests" - are extremely varied, not only botanically, but also from the economic standpoint. The feature they have in common is that they are inhabited by primitive peoples whose mode of life is generally harmful to the forest.
The figures in "The Forest Resources of the World,"2 recently published by FAO, show that in Africa out of a total area of 2,245 million hectares, 290.2 million hectares are covered by productive forest, and 526.7 million hectares by other forests. Other records show that only 309.3 million hectares are used for agricultural purposes. The productive forest area is unevenly distributed. The per caput area varies from 11.27 hectares in the Belgian Congo to 0.13 in Kenya and 0.02 in Somaliland. Of the 290.2 million hectares of productive forest, it is estimated that 137.6 million hectares are now accessible, comprising 767,000 hectares of coniferous forest, 136,173,000 hectares of broadleaved forest, and 627,000 hectares of mixed woods.
2 Unasylva, Vol. II, No. 4, p. 161.
Two broad categories of forests emerge:
1. Closed formations which include the dense, evergreen equatorial forests and certain high-altitude forests.2. Open formations which can be subdivided into two major classes: (a) shrub and thorny savannah formations of the Sahel type, and (b) the so-called "Sudanese formations" of Central Africa which include the seasonal forests (Guinean) and the tree savannahs (of the Sudan type).
There is a clear and constant relationship between the occurrence of each of these types of vegetation and the prevailing climatic factors. In Africa, there are two such factors of special significance, the annual amount of rainfall and the length of the dry season. Each zone has its own peculiar forest flora and, with a few exceptions, principally on the borders of the forest zones, there is very little merging of types.
Closed Formations: Rain Forests and High-Altitude Forests
This category includes what is usually and incorrectly called the "virgin" forest. Its area in Africa is much more limited than is generally believed, for such forests are found only on the west coast and in the central part of the continent. In French Guinea, the rain forest comprises a few isolated tracts with special characteristics in the Fouta Djallon mountains. It spreads out in Liberia and the Ivory Coast, the southern part of the latter being entirely covered by such forests with the exception of some few coastal savannahs, and in the Gold Coast it becomes an imposing mass reaching eastward to the plains of the Volta River. This main forest belt is then interrupted but appears again down in Nigeria where it merges into the immense equatorial forest which covers the larger portion of the Cameroons, Gabon, and the Congo basin in the French and Belgian territories.
These forests need minimum annual rainfall of 1,350 millimeters and can withstand only a short dry season, three months at the utmost. The forests are of very mixed composition and extremely complex in character. The Meliaceae is considered as economically the most important family. These are the trees that first made a name for the African forests. The mahoganies in particular, which are relatively plentiful in these stands, include many species of Khaya and Entandrophragma, such as: Khaya ivorensis (African Mahogany), Khaya anthotheca (Krala, Acajou blanc, or mahogany prefixed by the region of origin, e.g. Uganda), Entandrophragma cylindricum (Sapele, Sapelli or Aboudikro), Entandrophragma angolense and E. utile, etc. Among the species of this family mention may also be made of Guarea cedrata (Bossé, Diambi, or scented Guarea), Turreanthus africana (Avodiré or Lusamba) and Lovoa klaineana (Dibétou, Bombulu, or African Walnut).
The Leguminosae, less important commercially, is the most widely represented family, both by variety of species and proportion of growing stock. Several species may be mentioned: Distemonanthus benthamianus (Movingui), Brachystegia sp. (Bubinga), Erythrophleum ivorense (Tall) and Piptadenia africana (Dabema, Dahoma, or Bokungu). Among the Rubiaceae, the two most important commercial species are Mytragina stipulosa (Abura, Bahia, Vuku) and Sarcocephalus diderrichii (Opepe or Badi-Bilinga). The Gaboon okoumé, Aucoumea klaineana, of the Burseraceae family, is certainly the most important commercial African species on account of its relative abundance in pure stands and its reputation as a veneer wood. Finally, among the Sapotaceae, Mimusops heckelii or Makore; among the Sterculiaceae, Triplochiton scleroxydon (Obeche or Ayous-Samba) and Tarrieta utilis or Niangon; among the Moraceae, Chlorophora excelsa (Iroko or Kambala); among the Combretaceae, Terminalia superba (Limba, Fraké, or Afara) which is abundant in the Belgian Congo and highly valued commercially and Terminalia altissima or Framire. The ebonies of the genus Diospyros (Ebenaceae) must also be included.
There are two main climatic types and the classification generally used is that of the English botanists, who make a distinction between "rain forest," characterized by Triplochiton scleroxydon and "deciduous forest" characterized by such species as Azobé, Lophira procera (Ochnaceae), Niangon, and Avodiré. Beside these climatic types, another type is often found consisting of secondary forest with a predominance of light-demanding species, of rapid growth but little economic value. There are also a great number of edaphic types, such as mangrove forests consisting of Rhizophora species, coastal forests, swamp forests, etc.
The high altitude forests are not as homogeneous and their botanical composition is even more varied. They are found on the slopes of the Fouta Djallon Range in Guinea, in the western part of the Cameroons, and again in much larger blocks in Uganda, Kenya, Tanganyika, and Katanga, as well as in the mountain ranges of Ethiopia, and in the eastern part of the Union of South Africa, and a few rather degenerate stands exist in Madagascar.
In Kenya, for instance, above the dense forests at medium elevations, which are of no great economic value, the main species of the mountain forest proper is the evergreen Podocarpus, mixed to a greater or less degree with cedars (Juniperus procera) according to altitude. Still higher up come the bamboo forests, (Arundinaria alpina). In the Ruanda-Urundi, however, the bamboo is followed by another Podocarpus belt.
Open Tropical Formations
These include seasonal forests (of the Guinean type), tree savannahs (of the Sudanese type), and shrub and thorny formations (of the Sahel type). Bordering on the dense forest zone, the "Guinean" type zone covers fairly large areas of Africa. It is often termed "park land" forest which gives a good idea of its appearance. French foresters often called it la zone des grandes espèces sociales, because there are extensive pure stands of very characteristic species.
These forest types with several dominant species are found throughout Africa wherever similar climatic conditions exist. They form a vegetation belt, either subxerophilous or xerophilous, which stretches west to east from Guinea north of the Cameroons to Ubangi-Shari, then curves south and skirts the Congo Basin. In the north, the dominant species are Leguminosae of the genera Berlinia, Uapaca, and Lophira. These are replaced to the east by similar species of the genus Isoberlinia which, in the southern hemisphere, give place to Brachystegia. The Katanga, Tanganyika, and Nyasaland regions contain some fine forests of Brachystegia, mixed with Berlinia and Uapaca. Similar formations, such as the Tapia forests with Uapaca predominant, are found locally as far as Madagascar.
In the "Sudanese type" zone, the wooded savannahs are characterized botanically by species such as karite or shea tree, Butyrospermum parkii; baobab, Adansonia digitata; kapok, Bombax buonopense; and cailcedra or bastard mahogany, Khaya senegalensis.
These formations lie in regions with an annual rainfall varying from 500 to 1,000 millimeters and a rather long dry season lasting from seven to eight and a half months. One of the most important characteristics of this zone is that it consists of formations which are already very open, and in which the soil is covered with a continuous sheet of herbaceous vegetation. These immense savannahs burn every year during the dry season. The "bush fires" are ground rather than crown fires. Although the savannah trees have become resistant to fire, in the long run the damage caused to the stands is considerable, and it is obvious, as Professor A. Chevalier has pointed out, that the savannah fires which have been recurring for centuries act as a true climatic factor upon the forest vegetation.
Esquisse phytogeographique de l'Afrique
Shrub and thorny formations of the Sahel type which cover large areas of Senegal, Sudan, Nigeria, the Chad, the Anglo-Egyptian Sudan, eastern Africa, Rhodesia, and the southern part of Angola, are extremely open and scattered. Thorny species predominate, particularly the Acacias: Acacia senegal, A. arabica, A. tortilis, etc.
Since this vegetation exists with an annual rainfall of 200 to 500 millimeters through a long dry season extending over a period of from nine to ten and a half months, the trees are perfectly adapted to arid conditions. The ground cover is sparse and in some places even nonexistent.
It is necessary to study the evolution and role of these various types of forest lands in order to determine the problems of each zone. It may then become possible to deduce the measures that should be taken to preserve and improve the forest, and even to establish new stands; to judge the conditions under which it would be possible to tap these enormous resources as a means of improving the living conditions of the African populations; and also to help overcome wood shortages of other continents.
Although all authorities agree that the great rain forests once occupied much larger areas than at present, their complete disappearance is unlikely as a result of present abuses. What is actually occurring is impoverishment of the stands rather than real destruction; if, for any reason, the forest is destroyed, the vegetation cover appears again as second growth. The present impoverishment is due to the increasing amount of clearing for cultivation by the African populations and to present-day methods of exploitation which lead to the progressive disappearance of seed bearers of desirable species.
The importance of equatorial forest areas is threefold. In the first place, it can be safely assumed that the dense forests increase the quantity of annual rainfall, and this becomes particularly evident during the dry season. They also retain water in the surface layers of the soil much longer.
Secondly, there is the sociological aspect. In former times the people were dependent on the forests for food, clothing, and housing, as well as for medicinal supplies. Although they now have other resources, they still obtain a large portion of their requirements from the forest, and, most important of all, the forest affords land for crop cultivation. With the agricultural practices now in use, the forest constitutes the only source of renewable humus in this part of the world.
Thirdly, the potential economic value of the timber and other products from the forest is enormous. The main species of precious and common woods, hardwoods, semihard woods and softwoods of proven market value have already been listed, and it is estimated that these alone might provide an average supply of from 10 to 25 m³ per hectare. These figures are low compared to figures for managed homogeneous forests, and exploitation is always costly under such conditions. If the potential capacity of these forests is to be used more completely and if timber prices are to be lowered, it will-be essential to increase the number of species commercially acceptable and to cut logging costs. This is the major problem of African forestry. At the same time, the depletion of the stands resulting from uncontrolled cutting by the African populations and from unrestrained exploitation will have to be counteracted by controls, by progressive changes in agricultural practices, but, above all, by proper silviculture. This must be achieved either by introducing management of the forests being exploited or by undertaking improvement work in reserved forests. Purely protective measures need to be fairly limited in scope and confined to the mountain regions and the area bordering the savannahs.
The importance of the open formations cannot be denied but their degree of usefulness is debatable. It can be assumed that the presence of forest stands causes an increase in rainfall, atmospheric humidity, and the amount of water infiltrating the soil, and a decrease in ground evaporation. The forests of the Sudanese type are important to local populations as a source of supply for a number of products essential to their existence, but their general economic importance is of a much lower order. Some species, such as the Khayas and Dalbergia, produce beautiful woods, but the trees are often deformed; in any ease, they cannot be exported profitably, since they grow in regions far from the coast. However, certain species of real commercial value should not be overlooked, particularly the karite (shea tree), which provides a readily marketable oil seed, and the kapok, which supplies fiber comparable to the best plantation products.
The equatorial forest is not likely to disappear completely, but the Sudanese type formations may well disappear unless something is done immediately to save them. The two main dangers are clearing for cultivation and the annual burning which is highly injurious in all areas.
The forested steppe formations of the Sahel type have a major social significance. They cover vast territories and where they occur make possible the existence of nomadic or semisedentary tribes who depend on livestock. During the dry season, when the grass has totally disappeared, the thorny species compensate for the lack of rangelands because, by cutting branches, the herdsmen can feed pods and foliage to their herds. The indigenous populations also make extensive use of other forest products, particularly oils and tan stuffs. The effect of these formations on the climate is probably small but their role in binding sands and protecting croplands is very great. Their economic value is negligible although they supply some of the timber needed by the nomadic tribes and firewood for the settled communities as well as the wood required by public utilities, especially the river navigation companies. Gum arabic constitutes a commodity of considerable value in certain territories, such as the Anglo-Egyptian Sudan, French Senegal, and northern Nigeria.
These formations that reach to the borders of the desert are in a way a rampart against further encroachment by the desert. For this reason, they should be protected, regenerated, and, if need be, reestablished. Since climatic conditions are particularly unfavorable for forestry work of any kind, it is certainly in these regions that the forest services will face the most thankless and arduous tasks.
To arrest and counteract the impoverishment of the dense forests by improving the composition of the growing stock and its economic value; to ensure the protection and the reforestation of the forest areas in the dry regions - these are the foremost silvicultural problems of Africa. They would be difficult enough in highly developed countries, but in Africa, the enormous areas and distances and the difficulties of access make them infinitely more complex. Tropical silviculture is still in its early stages; its techniques have to be perfected and varied according to the composition of the stands, climatic conditions, and even local customs and populations.
Forest services and forest legislation in the various territories had to be created from scratch. It soon became evident that the initial requirement was a complete inventory of forest resources together with a thorough knowledge of the country and of local habits and requirements. The first step, therefore, was the making of botanical forest surveys, followed by the establishment of experiment stations to perfect silvicultural methods. On this basis it became possible to enact adequate regulations and to formulate and carry out work programs. Mention should be made of the men who pioneered this work, notably Thomson of Nigeria among the British; Jentsh, German; the Belgians, de Wildeman, Delevoy, and Tondeur; and Auguste Chevalier, Aubréville, and Humbert among the French.
The preliminary work is now progressing satisfactorily in most areas. In some, inventories have already been completed, and practical forestry measures can now be undertaken by the forest services.
Forestry in the Dense Equatorial Zone
It has already been pointed out that except in certain instances, the existence of the great tropical evergreen or rain forest is not seriously endangered and that the only problems which arise are those of arresting and counteracting the impoverishment of its stands and of increasing its economic value. The solution to these problems must be sought through silvicultural, agricultural, and legislative measures.
Foresters at first attempted to base their silvicultural activity on legislative measures alone since they lacked the personnel, equipment, and money to undertake any effective action along other lines. In the French territories, the "Berlin Rules" were a sample of this, but they soon proved ineffectual because of the difficulty of supervising their application.
There are two major schools of thought on African silviculture at the present time. The older is concerned only with the exploiting of certain well-known species, which have already been marketed commercially. It advocates intensive silviculture under the direction of the administration, the work to be concentrated on very small areas of "productive" forest reserves and carried out by competent technical personnel. Control over the rest of the forested area, which is economically of great value, is not abandoned but is limited to a strict regulation of the user rights of the people. A new trend, however, has recently become noticeable. In fact, it is a revival of the work of foresters in the Far East and even in Africa who recommended extensive silviculture, based on the utilization of a very large number of species. In such cases, the harvesting operation itself constitutes the actual basis of the silvicultural treatment. In order that the stands be affected as desired, it is essential that the cut should be sufficiently heavy and spread over a great number of species and size-classes. For this purpose a wide range of species must be commercially acceptable or at least be suitable for local utilization. For very sparsely populated regions - and there are many in Africa - such an intensive utilization is possible only if important woodworking industries exist or can be established locally. These industries should be fully integrated and capable of absorbing practically all kinds of wood. The industries will have to subject themselves to extremely strict cutting regulations, based on control by area, and in particular they will have to harvest within stated periods of time specified quantities of each species or of each of the major groups of species.
Legislative measures and regulations must therefore be closely related to the silvicultural methods decided upon. Those now in force first establish the ownership of the forest, whether by the State, the colony, the province or, sometimes, by the local community or by private individuals. The rights of usage of the people are laid down, since it is their abuse that has been most harmful to the forest in the past. Utilization rules still vary widely according to countries and the type of industry and product desired.
Most countries are at present studying ways of modifying and improving ancient practices of shifting cultivation and nomadic grazing. The effect of the farming demonstrations at Yangambi shows that some countries have already achieved interesting results in this field.
Forestry in the Savannah Zone
It is difficult to speak of work in the African savannahs as forestry. For the most part, foresters have to deal with vast open lands, which are sparsely timbered, have no stated ownership, and, what is more, are of very little economic value, so that the administrative authorities are inclined to pay very little attention to them. The practical difficulties of forestry work and the cost of silvicultural operations are heightened by the extremely unfavorable climatic conditions. Foresters consequently have had to proceed along even more extensive lines than in the dense equatorial forest areas, and their primary activity has consisted in determining and protecting the richer and more favorably situated forest stands.
In the Sudan-type zone, protection has to be afforded primarily against the devastating annual fires. The clearing of land for agricultural purposes is still carried out by burning, but as the fire is not controlled, the damage is out of all proportion to the object to be gained; excessive cutting on the other hand is relatively unimportant. The reserves which have been established are therefore merely areas protected by fire lines which surround and divide them, prevent destruction by the annual fires, and thus permit the original vegetation to re-establish itself. Sometimes it has become necessary to resort to artificial planting for climatic reasons or to ensure a supply of wood to settled communities, industries, and public or private utilities.
Techniques for the reforestation of savannahs were unknown at the beginning of the century but have made great progress since 1930 as a result of the work of the experiment stations where adequate methods have been developed and hardy and rapidly growing species chosen that are suitable to the climate of the regions. The two great enemies to planting are the grass that means fire during the dry season and threatens to stifle the young plants in the first years of their life during the rainy season and, above all, the climate. Tree species have to be of very rapid growth in their early stages in order to be sufficiently developed to endure the-first dry season. Silvicultural experiments have shown that there is no hard and fast rule in this respect and that, depending on the species and the local climate, it is sometimes best to plant stumps, sometimes half-grown plants and sometimes to undertake direct sowing of seeds. In the majority of eases the need for mixing crop cultivation with tree planting has been demonstrated and this practice has proved to be the surest as well as the most economical. Among the species that have proved most satisfactory are cassia, teak, the albizzias, etc.
In the formations of the Sahel type it is more difficult to fight deforestation because the stands are in an even more unstable state of equilibrium than in the Sudanese zone. However, some basic work is urgently needed in these regions because deforestation results in the progressive transformation of the land into desert and thus ultimately renders vast areas uninhabitable. The principal danger is overgrazing.
Brush fires are infrequent because the ground cover is irregular and the clearing of forest lands for cultivation over large areas occurs only rarely, except on the borderlands of this zone. Where they do occur, it is usually due to the introduction of large-scale cultivation advocated by the administrative authorities, whose obvious duty must therefore be to do everything in their power to remedy the harm they have caused.
The peoples living in these regions are generally nomadic and live by cattle raising and the harvesting of such products as gum. The flocks graze on the savannahs and destroy the natural regrowth of vegetation so that the stands become too open and, what is more, over-aged. They also suffer from the excessive cutting of branches for feed purposes. Whereas in certain regions, such as the Anglo-Egyptian Sudan, the tapping of gum trees is practiced correctly, in many others, in Mauritania and Senegal for instance, the trees are tapped too heavily and too frequently. It is imperative to cheek this abuse but, in the semidesert regions, with their wild nomad tribes, the problem is very often more political than technical, and too strict a control might cause an exodus to other more tolerant territories, and sometimes even provoke actual revolt. What was undertaken, therefore, on those territories having forest services, was the systematic setting aside of the finest forest stands as reserves. These reserves have been freed of all rights of user and outside them the exercise of rights is regulated.
In certain instances, and particularly with respect to gum tree stands, such methods have proved inadequate. It has been found essential to rehabilitate the forests and restock them. In some regions it has been found necessary to resort to actual planting in order to produce wood for domestic or industrial purposes. On the whole, however, the results have been poor, especially as regards the financial return from the operations. It has nearly always been necessary to water the seeds and young plants during the first dry season and consequently the expense has been entirely out of proportion to the results obtained. A few interesting projects have been developed on French territory (in Senegal, Sudan, and the Niger) and a rational plan has been drawn up for reforestation in Northern Nigeria. In 1937 an Anglo-French mission, whose purpose it was to combat the gradual advance of the Sahara desert, conducted a wide field survey and recommended certain measures, several of which were applied successfully.
Forestry in the Mountain Regions
Sometimes, the forestry situation in mountain regions is serious. The forest is often in an advanced state of deterioration, and this has far-reaching effects on the economic life of populations of the mountains and the plains. Extensive silviculture is possible, of course, but no quick results can be achieved. Here intensive silviculture is more advisable, in view of the climatic conditions which are particularly favorable both to indigenous and to exotic conifers. In Kenya, for example, excellent results have been obtained from plantations of cedars, Juniperus procera, pure or mixed with Olea chrysophylla and silver oak, Grevillea robusta, and also from plantations of exotic trees such as Cupressus macrocarpa, Lusitanica and Grevillea. At altitudes of 2,000 to 2,500 meters, Eucalyptus globulus, E. saligna and E. maculata, have also given good results. Plantation experiments with pure stands of pine from Indochina have been undertaken in French Guinea and in the mountains of the Cameroons. Elsewhere Grevillea and Podocarpus are used along with native broadleaved trees.
The two figures needed for an estimation of the potential forest output of a country are the surface area of the forest stands and the potential productivity of the forests per surface unit; these are difficult to obtain in Africa since only an infinitesimal portion of the forests has been explored, surveyed, and recorded. The problem is further complicated by the feet that absolute figures for Africa are of practically no value since they can only represent a "theoretical" potential production. In fact, under present-day conditions merely a fraction of the forests can be considered as economically accessible, and only a very few of the numerous species constituting these stands as technologically and commercially utilizable. Conditions, however, may change rapidly as nearly total utilization of large forest tracts is being envisaged.
Utilization Possibilities of the Wooded Savannahs
With regard to the possible utilization of the "dry forests" often classed as nonproductive, Aubréville has pointed out that the quantity of wood which can be extracted per hectare today varies considerably in these forests. The best wooded savannahs, those at Isoberlinia and Uapaca, can supply a maximum of 140 steres per hectare, which is equivalent to approximately 70 tons of wood. He allows as an average figure, 20 tons per hectare. Moreover, he is of the opinion that these stands could easily be worked as coppice, on a 20 years rotation, and that they would then produce 20 tons per hectare. An annual potential production of one ton of wood per hectare could therefore become possible for the Sudanese type savannah zone hitherto considered unproductive. If the stands in this zone were protected against brush fires and managed properly, they might then become an important source of forest products. At present it is believed that the extraction of wood under license amounts to only the two-hundredth part of this possible production, even though this was set at a very cautious figure. Account must be taken of local wood consumption for heating and housing purposes, but this could not be higher in these sparsely populated areas than one ton per inhabitant per year.
In view of the important part played by these wooded savannahs, from the general point of view of climate, soil protection, and water conservation, some foresters are against their utilization for fear that they might disappear. In fact, however, the danger of the destruction of forests through exploitation is less than that from brush fires and clearing for cultivation, for instance. It is difficult as yet to combat these destructive practices since the woods are considered to be of no economic value and their stabilizing role in the bioclimatic and bio-edaphic equilibrium of these regions is not sufficiently recognized. If, as a result of the creation of industries, these woods, hitherto considered useless, should acquire an economic value, so that proper forest management could be introduced, this would not only lead to their improvement, but also make it considerably easier to combat the main causes of deterioration. As Aubréville puts it in concluding one of his reports, it is sometimes necessary to find uses for the timber in order to save the forest.
Except for the question of manpower and the problem of transportation of the products, for which there is no easy solution, because of the distances from the coast, the exploitation of these savannah woodlands offers no serious technical difficulties. It is obvious that the wood should, as far as possible, be processed on the spot, and, except for local requirements, not be processed mechanically. The great equatorial forests are a far better source of supply for the mechanical industries whereas the species growing on the savannahs are by size and technological characteristics better suited for utilization by chemical and semichemical industries.
Utilization Possibilities of the Dense Forest
It is a fact that the dense forest zone of Africa constitutes one of the great wood reserves of the world. Estimates of the volume of standing timber in the great equatorial forests vary from 300 to 800 m³ per hectare. The wide discrepancy between these estimates is due to the variations in stand and the fact that some are based on all species found in the forest whereas others take into account only the trees considered of value as timber. Reliable authorities grant an average figure of 400 m³ of timber and 200 steres of firewood, a low figure leaving a safe margin. In order to get a rough idea of potential production, the figure of 400 tons of wood per hectare for standing timber would be a fair estimation.
Calculations and measurements have been made in order to determine more accurately the cubic volume of standing timber and the potential output of Africa's equatorial forests. The interpretation of each set of results can nevertheless give rise to a certain amount of criticism. Calculations made in the Cameroons based on a list of 40 species which can be used for sawn goods, and about 15 of which are already used commercially, have given the following figures: for the volume of mature timber, that is to say, trees which have attained the proper diameter for felling, 35 m³ of wood per hectare (28 tons of an average density of 8.8) for primary forest, and 20 m³ (14 tons with an average density of 0.7) for second growth. It has been further estimated, on the basis of surveys carried out in the Ivory Coast, that for trees having a diameter of between 30 and 60 centimeters, the average rate of growth in volume is 4 percent and that consequently the replacement of the forest capital from the middle age classes (i.e., trees with a diameter between 30 centimeters and the required felling diameter) is possible within 50 years, even if it is assumed as a margin of safety that during this period half the trees will be either damaged or destroyed.
It would therefore be possible, according to these calculations, to predict an output somewhere around 15 m³ per hectare annually, if all species were used for all accessible parts of the equatorial forests. This cut could be repeated after an interval of 50 years and could thereafter be continued for at least a hundred years. Elementary forest management of these areas would lead, on this basis, to a considerable output, without depletion of the growing stock.
Exploitation of these forests began in the early part of the twentieth century but did not develop to any considerable extent until about 1910.
There were primarily three major groups of hardwood species which were commercially exploited, namely: mahogany, okoumé, and limba. The exploitation of other species which are often grouped under the heading of "miscellaneous woods" assumed a growing importance in certain territories, and the development plans which are being drawn up at the present time are based primarily on increased production of these woods.
The apparent differences between countries of fairly similar conditions, particularly as regards total output and the proportion of sawlogs to total production, are due to variations in the method of estimating fellings for local consumption. Figures are obviously incomplete. Exploitation for export was never very great, for reasons given later, but it has constituted a stable and important part of Africa's economic life, as is shown by some export figures.
TABLE 1. - ANNUAL FOREST OUTPUT OF AFRICA1
|
Country |
Total roundwood |
Softwoods |
Hardwoods |
Total output of saw logs and veneer dogs |
|
Million cubic meters |
||||
|
ESTIMATED TOTAL |
50.0 |
1.0 |
49.0 |
4.00 |
|
Angola |
0.5 |
... |
0.5 |
0.07 |
|
Bechuanaland |
0.8 |
... |
0.8 |
0.01 |
|
Belgian Congo |
2.5 |
... |
2.5 |
0.45 |
|
Eritrea |
0.1 |
* |
0.1 |
0.01 |
|
French Cameroons |
3.7 |
... |
3.7 |
0.15 |
|
F. Equal Africa |
10.2 |
... |
10.2 |
0.20 |
|
F. West Africa |
0.8 |
... |
0.8 |
0.13 |
|
Gold Coast |
3.7 |
... |
3.7 |
0.25 |
|
Kenya |
1.0 |
0.1 |
0.9 |
0.17 |
|
Madagascar |
0.2 |
... |
0.2 |
0.02 |
|
Mauritius |
0.1 |
* |
0.1 |
0.02 |
|
Nigeria |
0.6 |
... |
0.6 |
0.28 |
|
N. Rhodesia |
0.3 |
... |
0.3 |
0.11 |
|
Nyasaland |
2.8 |
* |
2.8 |
* |
|
Seychelles |
0.1 |
0.1 |
... |
... |
|
Sierra Leone |
2.7 |
... |
2.7 |
0.01 |
|
S. Rhodesia |
2.1 |
* |
2.1 |
0.07 |
|
Tanganyika |
0.4 |
* |
0.4 |
0.11 |
|
Uganda |
0.3 |
* |
0.3 |
0.12 |
|
Union of S. Africa |
2.7 |
0.7 |
2.1 |
0.72 |
|
Zanzibar |
0.2 |
... |
0.2 |
... |
* Small
1 Excluding North Africa. Data by countries are official statistics reported to FAO and published in the Yearbook of Forest Products Statistics, 1947 and 1948 editions. The total is an estimated total.
There are several reasons for the partial failure of successive efforts to develop forest production in Africa. In the first place, since the stands are of very mixed composition and of relatively poor quality, it was necessary to adopt the practice of selective cutting with its high cost of extraction. This, added to high transportation cost, often made selling prices prohibitive, and exploitation, therefore, had to be limited to special and precious woods which did not compete with local woods in other countries.
The amount of utilizable, or rather marketable woods, was thus restricted from the outset; costs were high and the limited markets rapidly became glutted. As soon as utilization reached a certain level and any sizable quantity of these woods was offered for sale, disposal became difficult and very often the prices obtained were ridiculously low in relation to the value of the wood and the efforts of the firms engaged in extraction. There was a consistently large demand only for okoumé, but its production was limited for silvicultural reasons to a figure of 300,000 tons per year.
Under the original utilization conditions, it was always difficult to maintain a balance between production and consumption. This was one of the main concerns of the administrative authorities of the more important forest territories, as well as of the timber firms themselves, and failure to expand the African forest industries cannot be attributed to wrong methods but rather to an insufficient demand for tropical woods.
The principal cause for the high costs just mentioned is the relative poverty of tropical forests. Costs could be considerably reduced if the range of marketable species were enlarged. Experts, however, have always had considerable difficulty in getting trade and industries to accept new woods. There are several reasons for this, principally the technical difficulties of utilizing certain common species because of their properties which range from one extreme to another: that is, either extreme hardness or complete lack of resistance to attack or decay. Shortage of industrial plants and of sawmills in particular, and lack of adequate experience in working, processing, seasoning, drying, and preserving certain woods compelled the elimination of many common softwood species, with the result that only semi-hardwoods, hardwoods and sufficiently resistant softwoods were used. It should be further kept in mind that although some of the woods have admittedly poor mechanical or technological properties, the reluctance of buyers was also due in great part to conservatism.
TABLE 2. - 1947 TRADE IN AFRICAN HARDWOOD SAWLOGS AND VENEER LOGS EXPORTS BY DESTINATION
|
Destination |
Exporting Country |
||||||
|
Gold Coast |
French Equatorial Africa |
Belgian Congo |
Nigeria1 |
French West Africa |
French Cameroons |
||
|
Thousand cubic meters |
|||||||
|
TOTAL |
148 |
+213 |
+75 |
64 |
²60 |
37 |
|
|
Europe |
89 |
187 |
68 |
61 |
|
32 |
|
|
|
Belgium |
... |
5 |
51 |
... |
|
3 |
|
|
France |
... |
83 |
... |
... |
|
14 |
|
|
Netherlands |
... |
12 |
5 |
... |
|
5 |
|
|
Switzerland |
... |
19 |
... |
... |
|
... |
|
|
United Kingdom |
89 |
55 |
8 |
61 |
|
5 |
|
|
Other countries |
... |
13 |
4 |
* |
|
5 |
|
Near East and North Africa |
... |
2 |
... |
... |
|
... |
|
|
North America |
59 |
11 |
1 |
1 |
|
2 |
|
|
|
U. S. A. |
59 |
8 |
1 |
1 |
|
2 |
|
|
Other countries |
... |
3 |
... |
... |
|
... |
|
Africa |
... |
12 |
5 |
2 |
|
3 |
|
|
|
Union of South Africa |
... |
12 |
5 |
2 |
|
3 |
+ Total does not exactly correspond to the sum of the listed figures which have been rounded off.
* Less than 500 m³ ®.
1 1946 data.
2 Distribution by countries of destination not available.
Possibilities of Developing Forest Production
The reasons for past failures are now well known, and experts realize what to avoid. Great technical progress has been made, particularly as a result of research on tropical woods carried out in the laboratories of Princes Risborough, Nogent-sur-Marne, Gemblou, Yale, in the colonial experiment stations and also by industrialists and timber firms. To mention but one example, the limba of the Belgian Congo, for a long time considered unsuitable because of its lack of resistance to attack by insects and fungi, is now being treated with preservatives in ways that are both effective and economical so that it now commands an excellent position on European markets.
Wood requirements throughout the world have now increased, and the time is ripe for renewed efforts to expand African forest production, this time with every chance of success. It has been pointed out that one of the main obstacles to the introduction of new species on the markets was the conservatism of commercial and industrial users; full advantage should therefore be taken of periods of shortage to overcome this reluctance.
Utilization of the great African forests, which is desirable for both economic and social reasons, should be comparatively easy at this time. The fundamental ideas on which development plans are being based are roughly the following: First, the number of usable species should be greatly increased, primarily by a wider use of species with soft wood which can replace conifers for certain purposes; thus, selective cutting of only a few species will give way to rational and more economical exploitation because costs will be distributed over larger tonnages. Second, local processing industries, particularly sawmills, plywood factories, pulp factories, etc., should be introduced, again with a view to reducing prices but also for the more direct reasons of satisfying local requirements and conserving the forest. Finally, highly mechanized extraction and converting methods should be instituted in order to avoid waste of scarce and costly manpower.
One of the major obstacles to development at the present time is the lack of equipment or, what amounts to the same, the lack of foreign exchange to purchase it. Despite these temporary difficulties territories such as Nigeria, the Cameroons, Gabon, and the Belgian Congo are being gradually industrialized.
There are great areas in the north and south of this continent which lack forest resources. These are important wood consumers which will provide natural and stable outlets for this great potential production. As it develops, Central Africa will also increase its consumption and absorb more and more manufactured products. Finally, important foreign markets are already open, thus giving Africa the possibility to contribute, as it should, to abundance and stability in the world wood market.
