| Agro-forestry in the African Humid Tropics (1982) |
|Traditional agro-forestry systems: Prospects for development|
Traditional agro-forestry systems in the central African republic
Head, Forest Management Service, National Forestry Bureau, Bangui, Central African Republic
The Central African Republic is a land of forests, and yet its agrosilvicultural balance is being jeopardized by the lack of an afforestation policy. This paper contains a detailed description of the seven types of trees cultivated on many types of plantations and combined with food and other crops. The report also describes the traditional systems in use and proposes a series of measures aimed at improving their productivity. Finally, it is recommended that multidisciplinary research on soil protection end restoration be conducted, with the understandiny that human end social factors are of paramount importance in the restoration of tropical forests.
The Central African Republic is located between latitude 2° 16' end 11°20' N and longitude 14 20' end 27 45' E In the extreme north, between Sudan and Chad, is the Birao region, with which this report is mostly concerned. Here the climate is Sudano-Sahelian to the north and Sudano-Guinean to the south, and nowhere does the yearly rainfall exceed 1,000 mm.
Despite various botanical explorations, the vegetation of the area is still not very well known. The following divisions for the Sudanian forest were proposed by Sillons in 1950.
All of these formations may be grouped together in three regions: the first being that of the Bahr Aouk River (west of 21 E); the second that of the plains of Chad between the Koumbala River and Birao; and the third that of the areas of rocky relief south of Birao, around Ouanda Djallé and the Ouandjia Mines and along the Sudanese border. In the Bahr Aouk Zone, on quartzitic crests of the Old Precambrian period (sometimes with surface induration) grows woody vegetation composed of Daniellis oliveri, Anogeissus sp., Butyrospermum parkii, Parkia filicoidea, and Pterocarpus lucens.
In the Aluk-Aoukale zone one finds tree savannas where the most widespread woody plants are Terrninalia laxiflora, Hymenocardia acida, Prosopis africana, and Anogeissus. Actually, this is not a homogeneous zone, as there are also the main types of graminaceous pastures and dry termite forests with a tree layer of Khaya sp., Tamarindus indica, and Anogeissus and a shrub layer of Combretum spp., Cacia sp., and Bascia sp. Around the grassy plain of Lake Manoun, one may observe Borassus aethiopium, and Hyphaene thebaica, with Anogeissus, Butyrospermum, Tamarindus, Balanites, and Isoberlinia dominating. In the villages, alongside planted Ceiba pentandra, Moringa oleifera is found, which indicates a former Chadian occupation of the area. Between Dahal Hadjer and Tissi, Combretum savanna grows on the gaz (ancient aeolian sand fields).
Traditional Associations between Crops, Fodder Species, and Trees
The Central African Republic is a land of forests, and thus its inhabitants have no difficulty in obtaining wood. The Republic's forest belt covers the prefectures of Sangha, Sangha Economique, Lobaye, and the southern part of Ombella-Mpoko. Bananas, cassava, coffee, taro, some groundnuts, and some sesame are grown in these regions. The cultivation of all these crops entails the destruction of forests. All trees are cut down, with the largest trees being killed either by burning or girdling. After the forest has been cleared and all the plant material burned, the plot is ready for sowing. For all except two or three of the above-mentioned crops, the soil must be turned before seeds are planted. Since the crops must have full sunlight, not a single tree is left standing and the forest is irreversibly destroyed.
Moreover, since the tropical forest is rich in wood products, the people do not spare any trees when cultivating their fields. Coffee is one of the country's main cash crops, and a modern system of cultivation is followed. If, in this type of cultivation, one finds trees still standing here and there, especially on plantations belonging to the village people, it is because they feel that allowing the trees to remain will protect the coffee plants from over-exposure to the sun, thus increasing production. Generally speaking, no trees are left standing on large-scale coffee plantations. In cocoa cultivation, trees are preserved for their shade. This type of cultivation is not widespread in the Central African Republic because of the relatively unfavourable growing conditions for cocoa . Other crops are raised on land that has been cleared and burned, although sesame is often cultivated in pockets of savanna in the midst of the forest. Production per hectare is superior to that found in typical savanna regions.
The intermediate zone is located between the forest zone and the Vakaga zone. Its climate permits the cultivation of different types of crops. In this zone, where the majority of the population lives, cotton, sesame, groundnuts, and many other subsistence crops are cultivated. In Basse-Kotto and Mbomou, even coffee is grown. The crops are raised on Sudanian savanna where tree density per hectare is considerable. This means that the forest must be completely destroyed except where trees are of some use because they provide edible fruit, shade, or some other byproduct for which the farmer feels there is a need.
The trees are carefully preserved in Birao (which is roughly in the middle of Vakaga prefecture) as wood is the primary fuel for cooking and lighting. As the rainy season approaches, inhabitants lay in a supply of firewood to tide them over until the next dry season. Inhabitants of this region traditionally protect "useful" trees that grow in their fields -useful because they provide fruit, oil, medications, and fodder for livestock.
There is a noticeable lack of industrial-scale cultivation in the Vakaga region. The population depends primarily on subsistence agriculture, sheep-herding, hunting, and gathering. There are approximately 15,000 inhabitants of the Vakaga prefecture, with a population density of 2 people/km². The Vakaga prefecture is divided into two subprefectures, Birao and Ouanda Djalle. The region's chief town is Birao. All Ministry of Rural Development services are represented there: agriculture, animal husbandry, and forestry. The latter is further divided into three sections (Birao Centre, Gordil, and Ouanda Djallé) with ranger stations and patrol areas.
The Vakaga region differs from other regions of the Central African Republic in that cassava has been introduced there fairly recently. Millet is grown in light, sandy soils and its abundant foliage is favoured by horses and cattle. Two varieties of Sorghum candatum are found, as well as Sorghum vulgatum, an intermediate variety, and red and white berbere (the term is used to describe heavy, compact, clayey soil and also for several varieties of Suorghum durra). Groundnuts are cultivated, but maize is not very widespread since it is simply planted around huts as a back-up cereal.
The population of the Vakaga region consumes vast quantities of roselle (Hibiscus sabdariffa), whose calyx and early fruit are used as ingredients in couscous and whose flower is used in herbal teas. This malvaceous plant is almost always planted in millet fields and around huts. Hibiscus esculentus (okra or gumbo) is one of the most common field and garden vegetables. Sesamum indicum (sesame) is planted in sandy soil, especially in fine sand, where its yield is excellent. Cucumis sativus (cucumber, or fagouss) is one of the most widely cultivated vegetables, and this is often cultivated together with squash.
Trees Recognized as Useful
Vegetation in the Vakaga region, as in most Central African regions, has been greatly affected by human intervention. Over-grazing has sometimes caused the almost total disappearance of woody vegetation in some areas. Vast stretches of desert can be seen around Birao, even though climatic conditions warrant the growth of abundant thorny vegetation. Nevertheless, six trees are recognized as being particularly useful: Balanites aegyptiaca, Butyrospermum parkii, Parkia biglobosa, Borassus aethiopium, Adansonia digitata, and Tamarindus indica. This is proof that, even when the inhabitants do not try to protect trees in their fields and incorporate them into their farming system, a certain equilibrium between agriculture and silviculture is sometimes established.
Throughout the Birao region, Balanites aegyptiaca is carefully cultivated because of its many uses. Its fruit provides an oil that is often used in cooking and some old people will eat only sauces made with Balanites oil. The sulphur-yellow flesh around the pit is eaten in much the same way as chocolate. The tree is often stripped by livestock, which favour its foliage, and also by herders, who cut off branches to build shelters for their calves. Treated in this way, the tree acquires a straight trunk. Village people use it as the main member in the frames for their huts, because the hard wood resists attacks by termites. The wood is also used to make handles for spears, axes, and other tools. Villagers are fond of eating fried beef liver on Balanites aegyptiaca leaves, which are reputed to cure liver ailments. Sometimes there are clashes between stock breeders and village people, not because livestock have destroyed millet fields but because a herder has cut branches from a tree to make a bed. This species more or less covers the northern part of the area, and three or four of these trees can be found in even the smallest fields. Its many uses cause it to be cultivated also in Bangui, the capital of the Central African Republic.
Butyrospermum parkii .(karite, or shea tree) is characteristic of the region. It provides a fleshy fruit and a stone whose oil extract is valued as a preservative. Farmers gather the bark to make beehives; this usually kills the tree. In some villages, this practice is forbidden by tradition, except for trees that have been declared unproductive.
Parkia biglobosa (nitta) is a leguminous mimosa producing pedunculate fruit and a yellow powder eaten by the local inhabitants. The seeds are boiled, fermented, and used to make a tasty sauce for eating with Hibiscus esculentus (okra). Village people often set their beehives in this tree.
Borassus aethiopium (palmyral is widely used in this region. All huts constructed by the government are made from planks from this tree, rough-hewn locally. Since the palmyra resists termites, it is also used locally in the frames of huts. The flesh of its fruit is eaten by village people; elephants are also fond of it and can sometimes even be seen in an inebriated state near large stands of palmyra. Young shoots are gathered and marketed as in other regions.
Adansonia digitata (baobab) figures in African mythology and is greatly revered. The local inhabitants make sacrifices under this tree. Shoots are eaten in a smoked fish sauce. The tree is found throughout the area but is practically non-existent in places where elephants have come to rest, for they strip the tree of its bark. The white powder around the seeds is eaten in the same way as chocolate.
There are several varieties of Tamarindus indica in Birao. Some do not sprout leaves until the start of the dry season; their fruit is picked toward the end of this season to feed livestock (sheep and kids). Others, however, have year-round foliage. It is this second kind that is usually found in fields and villages. It produces a very sour fruit thought to be a good cure for colds because it is rich in vitamin C. The branches are gathered, boiled, and used as a medicine for fevers, rheumatism, and fatigue.
Oxytenanthera abyssinica (bamboo) must be added to the six described above because of the role it plays in local construction. It is used for roofing and especially for fences, for the region is Moslem and each hut must have a fence around it.
The theory that some sort of balance must be established between agriculture and silviculture presupposes the maintenance of an ecosystem. The ecosystem is greatly influenced by climatic, biotic, human, and soil-related factors, but must be continuously maintained by agronomists, veterinarians, and foresters. Such multidisciplinary activity is difficult. When farmers in the Vakaga region allow trees to remain standing, the reason is that they derive some products or service from the trees. This explains why, although there is indeed a certain traditional agro-forestry system, its aim is not just to preserve trees or to ensure a certain equilibrium between agriculture and silviculture. Thus an information programme should be set up to teach agro-forestry methods in the areas concerned.
An information campaign presupposes an established plan ready for execution. Consideration should perhaps be given to the application, in this region, of all silvicultural methods used to date in wet forest zones and savanna: the taungya method, the Malayan uniform system, the tropical shelterwood system, the semi-selective management system, the cross-ride method, full-capacity planting, and restricted grazing Some of these methods can be applied only in forest zones, but taungya, full-capacity planting, and restricted grazing (which is the most economic and most important method), could be widespread. Initially, farmers in central Birao should be organized into three groups, according to the kinds of crops that suit each system. The first group would adopt the taungya method; the second and third groups would practice full-capacity planting and restricted grazing, respectively. Later, all three systems could be applied in every village of the Vakaga region, depending on the crops grown and the environment, the main factor being the dominant species of tree. A five- or six-year rotation would suffice to allow the rural population to grow crops on land enriched by fallowing to improve its yield.
The taungya method may be practiced in conjunction with full-capacity planting and restricted grazing. In heavily treed areas where the dominant species of trees are those that farmers are in the habit of preserving and growing in their fields, the taungya method will be applied. In Birao Centre, Ouanda Djalle, and the rural areas in these two subprefectures, the same method will be used but the kinds of crops will vary depending on the farmers' means of livelihood. This will give rise to a wide diversity of crops being raised in conjunction with Balanites aegyptiaca, Parkia biglobosa, Butyrospermum parkii, and Tamarindus indica, which are the only local trees suitable for the taungya method and restricted grazing. Even if the taungya method and fullcapacity planting fail, restricted grazing (which is the least costly method) will undoubtedly be successful if brush fires and human factors can be contained.
From the example of other African countries, it can be seen that farmers automatically preserve useful trees in their fields. However, it should be noted that this still does not provide the level of forestation necessary to maintain a favourable climate and soil fertility.
Other solutions may be considered, such as:
The immediate result of this activity will be to check deforestation around the city of Birao and the villages in that region, and to create an environment favourable to reforestation. Over the medium term, the main objectives will be to combat soil erosion and to make local inhabitants aware of the forest's usefulness and of the adverse effects of systematic deforestation on agriculture. Over the long term, the forest cover will be re-established and city-dwellers will be supplied with firewood through cuttings on a rotational basis.
This work will involve considerable multidisciplinary research on soil protection and restoration in each ecological zone, keeping in mind agriculture, animal husbandry, and forestry -without neglecting the human and social aspect. Customs are so important that nothing can be accomplished without a great information, popularization, and organizational campaign. The future of our tropical forests depends on it.