FAO Forestry Department
This article has been adapted from FAO Forestry Paper 50, Changes in shifting cultivation in Africa. It is based on a comprehensive study carried out by the Forestry Department in 1982-83 and coordinated by a working group which included officers of the Agriculture and Economic and Social Policy departments of FAO, as well as a sociologist from the Overseas Development Institute, UK (Dr Clare Oxby).
· Shifting cultivation in a variety of forms has been practiced successfully and safely for centuries, fully adapted to the specific climatic and edaphic conditions prevailing in a given forest region. However, because of increasing population densities and escalating land pressure, this is no longer the case in most of tropical Africa. Changes in the patterns of land use, both spontaneous and planned, have taken place in which forestry and forest trees have played a vital role; yet further changes must occur if Africa is to avoid fatal soil degradation and produce the food its inhabitants require.
The term shifting cultivation has been applied to a wide range of cropping systems; here, following FAO convention, it refers to "a system in which relatively short periods of continuous cultivation are followed by relatively long periods of fallow" (FAO/University of Ibadan, 1982). It is thus distinguished from short fallow and permanent cultivation. By this definition, shifting cultivation is no longer as common in Africa as formerly; moreover, it is usually combined with other forms of agriculture. According to an FAO study, "the main humid area where shifting cultivation remains the dominant form of farming is the middle belt of West Africa, between the coastal tree belt and the more permanently farmed northern plains. It is also still found in sparsely populated areas of Tanzania, Zambia and northern Mozambique and in the empty area of the Zaire basin" (FAO, 1984, p. 9).
In areas where population density is high and land in short supply, shifting cultivation in its traditional forms is neither appropriate nor possible, for it requires the "luxury" of land that can be held in long-term fallow. It also commonly involves the frequently criticized practice of clearing by fire. From the farmer's point of view, burning has a number of positive features: it is labour-efficient, the ash produced is a valuable fertilizer, the leaching effect increases the availability of soil nutrients to plants, and it may kill fungal diseases and noxious insects. In addition, many farmers prefer to clear forest regrowth rather than high forest. When useful trees are involved, they normally protect or extract them before burning. Lassailly-Jacob (1982) is not alone in arguing that what is needed now is advice to farmers on how to use fire and control it more efficiently, rather than sweeping fire prevention.
Social change in Africa over the last few decades has been characterized by increasing population densities; the expansion of areas under cultivation, largely through the introduction and expansion of cash cropping; increasingly difficult access to land; and the increasing participation of small communities in regional, national and international markets. Changes in agricultural techniques can be understood in this framework, for what has been happening in Africa is that these techniques have been adapting fast (although in some instances not quite fast enough) to the changing circumstances, in particular the decreasing availability of land.
Since shifting cultivation involves long periods of fallow, a large amount of land is required per family, most of it unproductive at any one time. It is simply not possible to practice shifting cultivation when population densities rise and there is not enough land to leave a satisfactory period of fallow. However, just how high a population density shifting cultivation can support is a matter of some debate. While Ruthenberg (1980, p. 62) calculates that no more than 56 persons to the km² can be supported, Lassailly-Jacob ( 1983) estimates that in Beumi, Ivory Coast, the present density of 83 inhabitants to the km² could be raised to as much as 123 without destroying the environmental balance. It is therefore important to distinguish between absolute population density and population density in relation to the extent and fertility of cultivable areas.
SLASH-AND-BORN IN THE IVORY COAST part of the shifting cultivation cycle
There are many possible reactions to changing situations in rural areas; different agricultural techniques may be employed, or, more radically, rural exodus may occur. Faced with land shortage, farmers may turn to crop rotation as they have in Tiv, Nigeria (Vermeer, 1970), and Baoulé, Ivory Coast (Lassailly-Jacob, 1983), or increase the intensity of cultivation by shortening the fallow period as has happened in northeastern Zambia (Lawton, 1982). This latter strategy, however, is rational only up to a certain point, beyond which any further decreases in the fallow period would result in soil degradation and decreasing yields. At this stage, a more radical change has to be made from fallow agriculture to permanent agriculture. Boserup (1965, p. 26) gives a general example:
A radical change in part of the area
A growing rural population does not produce additional food by increasing the number of times the land is ploughed or by weeding of fields under short-fallow cultivation which were hitherto left unweeded. Instead of such changes, which would not add much to total output, short-fallow cultivators are likely to take to annual cropping on a part of their land. This transition in its turn may call for the introduction of better ploughing, irrigation and weeding - or the shortening of fallow may have as its necessary concomitant the production of fodder crops for the animals. In other words, the additional labour is likely to be used as a means to undertake a radical change of the system of cultivation in part of the area, while no change is made in other parts of the area.
The first plots converted by this change to permanent agriculture are usually those nearest the house site; animal, vegetable and general household refuse is used to fertilize gardens around the house where all kinds of vegetables, root crops and fruit trees are grown. Together with more permanent forms of cultivation go more permanent forms of housing.
It has been demonstrated that the more intensive the agricultural technique, excluding mechanization, the worse the returns to labour.
The main purpose of the fallow period in shifting cultivation is simultaneously to improve soil fertility and the soil's capacity to resist erosion. There is evidence that the length of fallow period can be decreased to a certain extent without seriously compromising these functions (Jean, 1975). The actual length of time obviously depends on a variety of factors, such as soil and vegetation type, and intensity of previous cultivation of the area. Another factor is weed control: in wetter climates, to prolong the period of cultivation implies the need to apply more sophisticated weed management techniques or to spend more time on this work.
Given the increasing cultivation period and decreasing fallow period consistent with increasing land pressure, at a certain stage yields can only be maintained or improved by the use of fertilizer. If chemical fertilizers are too expensive or not available, if manure is not available because animals are not kept, if the use of "green manure" is found to be too labour-intensive, and so on, then there is a likelihood that increasing land pressure will result in soil degradation. If yields continue to decline under these circumstances, members of the farming households may look for paid jobs, often in urban areas, to contribute to family income; or some or all of the family may migrate to another area where land pressure is not so great.
There has been wide discussion on the reasons farmers frequently resist change until the process of decreasing yields and soil degradation has - often irreversibly - set in. Why can they not change before this happens? There are many explanations, some of which may apply to some areas and not to others:
· It has been demonstrated that the more intensive the agricultural technique, excluding mechanization, the worse the returns to labour (Boserup, 1965, and others since). Thus, for example, in Sierra Leone, a change from upland rice under shifting cultivation to swamp rice under permanent cultivation generally represents an increased labour requirement.
· In cases of soil degradation; it is often discovered that the farmers concerned have no long-term security of land tenure; in other words, they will not necessarily benefit from soil conservation measures - their landlords will.
· Switching to a new agricultural technique represents a risk which may be unacceptable to farmers who only just manage to satisfy their subsistence requirements. Such farmers will wait until others have tried and succeeded before they themselves try.
· Switching to a new agricultural technique may require capital investments which the small farmer cannot afford or which are difficult to obtain locally (fertilizers, improved seeds, etc.).
· Making the new technique profitable for the small farmer may depend on easy access to markets and access to transport; in some areas these conditions may not exist.
Some of these factors are illustrated by P. Richards (1977) in his description of the deteriorating conditions facing the farmers in the Ikale region of southwestern Nigeria where, between 1952 and 1963, the population growth rate was about 7 percent:
Something of a crisis in man-land relations
The conclusion is that although shifting cultivation may survive... for some years to come, something of a crisis in man-land relations is developing in both Idapomarun and Orisunmeta districts. Pressure on land has already led to far-reaching changes in the agricultural economy, but there can be little doubt that further change is called for. There are four probable directions in which such changes may occur. First, evolution towards permanent cultivation of annual crops must almost certainly take place, perhaps via a "compound land", farming system as practiced in parts of eastern Nigeria... Secondly, there is likely to be continued increase in the acreage planted to tree crops, especially oil palm. This is an understandable if not entirely satisfactory development since tree-crop plantations provide an assured cash income, are much less prodigal of land, and once established require less labour to maintain than annual-crop farms.
Thirdly, the number of farmers engaged in part-time trade and manufacturing and in plantation labour will continue to grow... Finally, the pressure of people on land remaining unabsorbed by these three kinds of changes will continue to seek an outlet in that long-established stand-by of an under-occupied rural labour force, migration - especially migration to the major urban areas.
Apart from rural-urban migrations, there can be a less obvious but equally important type of migration: that of farmers from areas of higher population density into neighbouring rural areas of lower population density. Such migrations vary according to the distance travelled and the extent to which the agriculture practised in the homeland differs from that practiced in the new lands. In some cases, such migrations represent an attempt to find farming conditions comparable to those found in the homeland.
In situations of change, it would therefore be inaccurate to think that farming systems are adapted only in the direction of intensification of agriculture. They usually are, but this is by no means always the case, for migration from high to lower population-density areas may be accompanied by an extensification of agriculture. Grossman (1974) cites the example of seasonal migrants in east Nigeria who travel to Nikemand, north of Enugu, where they take out yearly leases from local landlords to grow food crops. The Bemba of Zambia apparently learned their practice of shifting cultivation from local farmers when they left their previous homelands in Lubaland (A.I. Richards, 1939).
Another example of migration from high to lower population-density areas is the important migration route into the humid forest zone of West Africa from the subhumid and Sahelian zones in the north. Until recently, the southern forest zones were inhabited mainly by farmers in low densities practicing shifting cultivation. Rapid changes in land use were observed in Ghana during the 1940s, 1950s and 1960s, when much of the country's southern forest, opened up by logging roads, was turned over to the cultivation of cocoa (Hill, 1963); a similar process occurred in neighbouring Ivory Coast, with both large-scale and smallholder plantations of coffee, cocoa and oil-palm.
Such migrations and changes in land-use patterns have, of course, had profound consequences on the local farmers. Following the example of large-scale private and state perennial cash-crop plantations, in which they provided much of the labour-force, many of them have turned to permanent cultivation of perennial cash crops in addition to their subsistence farming. This suggests that the lack of roads and of access to markets can be an important factor in determining the local people's way of life, and that as soon as conditions change and they have access to markets, they may switch to a way of life that is more profitable to them.
It is incorrect to think that shifting cultivation in all its forms is an unsatisfactory form of land use.
The migrant farmers have sometimes been confused with the local farmers and misleadingly called shifting cultivators, since they plant food crops in the early years of plantation establishment. However, the term is inappropriate, because food crops are only tolerated as long as they do not rival the perennial agricultural crop species, and the latter are not grown to regenerate soil fertility for food crop production (de Rouw, 1979). One consequence of this change in land use from shifting cultivation to perennial cash crops is that the more forest land is cleared for plantations, the less is available for food crops. The local farmers are likely to suffer most in the long run, since once their land runs out they have nowhere to go, while the migrants often retain links with food-crop-growing relatives in their area of origin and, having moved at least once, may find it easier to move again.
It is incorrect to think that shifting cultivation in all its forms is an unsatisfactory form of land use. Okigbo (1981) says that bush fallow systems can be stable, ecologically sound and efficient, while Nye and Greenland (1960) argue that, until now, there has been a failure to evolve a superior method of stable food cultivation in the tropics. It should be stressed that problems of land scarcity, soil degradation and diminishing yields are associated not so much with shifting cultivation as with short fallow cultivation in areas where shifting cultivation was once practiced but where conditions have changed; the result is that it is no longer possible to leave a long fallow period, and the fertilizer and other inputs needed for more intensive land use are too expensive or are unavailable.
Priority planning should therefore concentrate on those "crisis" areas of short fallow cultivation, not on those areas where it is still possible to restore soil fertility and forest vegetation by sufficiently long periods of fallow. One type of planning concerns the improvement of fallow cultivation; the other concerns its replacement with other forms of cultivation. In both cases the role of trees is of utmost importance, because planted as well as natural trees help control erosion, suppress or eliminate herbaceous and woody weeds, and restore soil fertility (Grinnell, 1975). Alternatives to fallow cultivation that have involved complete land clearance, including destumping, and a change to other forms of agriculture without trees - for example, annual crops - have often been unsuccessful.
Jurion and Henry (1967) and Tondeur (in FAO, 1956) describe the attempt in the then Belgian Congo to regulate shifting cultivation by the "corridor system": delimiting strips of land which were to be cleared and then left fallow according to an overall plan for a particular area. These efforts failed for a variety of reasons (Ruthenberg, 1980). On the technical side, such a regular division of the land meant that it was impossible to respect the different parts of the land. On the socioeconomic side, these efforts lacked the cooperation of farmers. Many were forced to move to new villages associated with the scheme; in addition, since they were obliged to grow a certain quantity of cash crops like oil-palm, they saw these changes more as a method of social control, tax collection and cash-crop extraction than as a means of improving their agricultural techniques.
A second method for improving shifting cultivation - substituting artificially established woody legumes for natural bush fallow vegetation - is an old idea of proven value for edible varieties of pigeon pea, but the potential of the technique for other woody legumes which yield firewood and other byproducts, while at the same time contributing to the restoration of soil fertility, has yet to be explored (Raintree, 1981). However, there are a number of trees and shrubs that could help increase the speed of reestablishing soil fertility (Raintree lists 13 promising species).
Although a number of projects and field trials are being carried out in several countries, there is as yet little information on the implementation of planting in fallows and the acceptance of the principle by farmers. In Madagascar, a successful project has involved planting Grevillea during the fallow period after the cultivation of hill rice, maize and beans. In Benin, a government programme has encouraged small farmers to plant Acacia auriculiformis in their fallow land in order to enrich the soil and at the same time produce fuelwood quickly; however, farmers have been slow to accept the idea, because they have not yet appreciated the soil-enriching properties of the tree and still prefer teak and eucalyptus, whose stems are valued for their medicinal qualities. A major problem with the scheme is that rapidly increasing population increases pressure for food crops, so that the fallow period is gradually being reduced, and much of the soil-enriching contribution of the acacia is being lost. The long-term aim of the project - to switch from fallow field areas to planting acacia in rotating rows with food crops - may be hindered by the lack of opportunities for marketing surplus produce (Tran Van Nao, personal communication, 1983).
A third method for improving shifting cultivation is to make better use of cleared vegetation. The assumption - which, as already suggested, is partly misleading - that burning vegetation is wasteful is the basis of a number of attempts to replace fire with other techniques of clearing. One such effort has been named "the Subri conversion technique", after the Subri Forest Reserve in Ghana where it was developed. Most of the cut vegetation is extracted as sawn lumber, some as charcoal, some as fuelwood, and some for small local industries like carving and basket-weaving. The remaining small branches and leaves are used as green mulch for the agricultural crop.
TOUAREG MIGRATION IN THE NIGER seeking a place to grow food
Although field trials have already been carried out within the forest reserve and results published (Earl, 1982), no effort has yet been made to introduce the technique to farmers outside the reserve. The field trials indicate that income exceeds expenditure; however, the direct costs are about 2.9 times those of ordinary cut-and-burn methods and require about 37 percent more labour (Earl, 1982). These last two facts probably mean that to the small farmer with limited capital and labour resources, the new technique is not a feasible proposition. Moreover, the trials comparing the Subri conversion technique with the cut-and-burn technique have taken into account forest tree production, not agricultural crop production, which is, of course, what the farmers are primarily interested in.
Finally, the vegetation to be cleared inside and outside the reserve is rather different. Therefore, the results of trials inside the reserve may not be applicable outside, where there is no high forest left and where vegetation is being cut after only a few years' growth. For all these reasons, farmers may have a cautious outlook in relation to any technique without burning, unless, of course, the farmers themselves are to make significant profits, for example from increased sale of charcoal, timber or food crops.
One of the alternatives to shifting cultivation is the taungya system of large-scale forest plantation establishment used by forest departments, in which food crops are interplanted with trees in the early years of the plantation. Two broad types of taungya can be distinguished, depending on the farmer's role: (a) "individual" taungya, or "own your own crop" (Olawoye, 1975), where the farmer plants trees in return for use of the land for a limited period of time; and (b) "departmental" taungya, or "farming for pay", where the farmer carries out jobs for the forestry department related to plantation establishment and agricultural crop production in return for a wage. While there are many accounts of the profitability of taungya from the point of view of forestry departments, which find it a low-cost system of establishing plantations, there are few accounts of how profitable or acceptable taungya is from the farmer's point of view.
Under a system of individual taungya, farmers are given access to plots of land on which they must plant trees which are the property of the forestry department. In return, they may cultivate the spaces between the trees with food crops, the produce of which is theirs. Depending on the crops and trees grown, and forestry department regulations, the farmer may cultivate the land with certain prescribed crops for between one and three years, after which time the trees will have grown enough to shade out any food crops. At this point, the farmer has no other choice but to move to another area. If the forestry department is continuing to plant trees in the same way at this time, and if the department is pleased with the way the farmer has looked after the saplings, it may offer another plot for use. If not, the farmer will have to search for land elsewhere.
As an alternative to shifting cultivation, this is likely to represent a move from greater to lesser security of land tenure for farmers accustomed to having permanent customary rights to land outside forest reserves. The farmer who is allocated one plot after another may have a certain illusion of security; in practice, however, reforestation programmes do not continue year after year, and there always comes a time when no more land is avail able for taungya. Furthermore, there may not be enough land in the forest reserve for everyone who would like access to it, so some farmers have to do without.
Since the farmer has no long-term rights to the land, there must be short-term incentives. One of these is access to arable land where such land is scarce. Ball and Umeh (1981) state that taungya has not succeeded where there is other fertile agricultural land available. The other short-term interest is in the one to-three-year agricultural crop. But since this crop is much reduced in relation to the area cleared because of the space and labour devoted to the saplings, it is clear that the farmer would choose this system only if there were no means of access to other, similar land.
Because of these factors, it is understandable that forestry departments have had problems administering the system. For example, when taungya was introduced in Togo in 1958, the combination of restrictions on the kind of crops that could be grown and the very principle of setting aside forest reserves to which people felt they had inalienable customary rights triggered off a wave of protests. These led to the system being suspended in the early days of independence (United Nations University, 1982). Taungya was reintroduced in 1972 with FAO assistance, but this time with added bonus incentives in cash and in kind. However, two problems were faced: first, the farmers objected to the fact that it was not possible to carry out crop rotations; and second, the plantations were far from the villages. Since there was no shortage of grassland around the forest reserves and nearer the settlements, the plantations were deserted in favour of the less fertile agricultural land.
In Nigeria, three types of bonuses were being considered in 1981: subsidized food obtained from departmental taungya; assistance with land-clearing, crop-processing and storage; and cash bonuses for successfully planted trees (Ball and Umeh, 1981). However, the effectiveness of even these bonuses remains uncertain.
Individual taungya was introduced to Ghana in 1928 in order to satisfy the farmers' demand for arable land in areas of land shortage and the foresters' desire to establish a tree crop at reduced cost; the farmers bore the cost of the major expenditure in plantation management - site-clearing. According to Brookman-Amissah (1978), success was not commensurate with effort since, as in Togo, the early plots were small, scattered and not easily accessible and did not constitute manageable plantation units. Moreover, the tending of the tree crop was inadequate, especially after the farmers had left the sites. In 1968, the forestation effort in Ghana was intensified, which meant a sudden increase in the amount of land available to the taungya farmers, perhaps more than they really needed for their subsistence agriculture or could cope with. One of the consequences was that taungya came to be dominated by big farmers, who found the large tracts suitable for commercial farming; small farmers were being overlooked. In an attempt to solve these problems, the Forestry Department introduced a system of departmental taungya in 1969.
In Liberia, an alternative way of controlling the amount of land available to each taungya farmer was introduced by the Forestry Development Authority (FDA) in 1974. Land preparation, up to and including the phase of burning, is carried out by the FDA, and then the farmers come in to plant one rice crop at a nominal fee. A fee is charged to control the acreage given to each household and to help retain part of the cost for land preparation. The main benefits are reported as reduction in the cost of reforestation, as farmers perform the initial task of tending the plantations, and an increase in the production of upland rice through an increase in cultivated acreage and improved seeds (Appleton, 1982). From the farmer's point of view, this system looks like a yearly tenancy.
In Sierra Leone, there are two variants on individual taungya (one, unfortunately, only at the proposal stage and the other at an early stage of implementation), which have particular implications for the farmer. The first is similar to the Liberian example in that farmers would pay an annual rent, though it is not clear whether they would be helped in clearing the land. The difference from any other taungya system considered here is that the agricultural crops are not annuals but perennials such as coffee, cocoa and cola as understoreys in Terminalia ivorensis and Terminalia superba plantations. Providing that the arrangement could be renewed, this system could provide the farmers with a tenancy arrangement for at least 20 years, or as long as the life of the particular crop, thus providing a great deal more security of tenure than that connected with annual crops.
The second variant is a proposal for community fuelwood plantations and community forestry plantations to be established by Sierra Leone farmers under the taungya system. Farmers, however, would benefit not only from the food crops planted in the early years of establishment but also from the forest trees, for they would be allowed to keep the proceeds of any harvesting of such material that they undertake, subject perhaps to payment of a small licence fee ( FAO/World Bank, 1982). Because the farmer is to profit from the forest trees, this proposed system might be more appropriately considered agroforestry than taungya.
CLEARED FOREST PATCH IN GABON ready for planting
Departmental taungya is distinguished from individual taungya by the fact that the produce from any agricultural crop belongs to the forestry department, which rewards the farmer with a wage. From the farmer's point of view, therefore, departmental taungya is like other types of paid agricultural labour and radically different from individual taungya. Under the latter system, the farmers depend on their food crops for survival and thus are highly motivated to take care in growing it, whereas under the former system the paid labourers are only motivated to the extent that they will continue to collect their wages. It is therefore not surprising that forestry departments complain of "lack of discipline" among their taungya workers and that administrative costs are high.
A further difference between the two systems is that whereas individual taungya attracts mainly local farmers, departmental taungya may also attract people from other areas, and even from towns, who are in search of a wage. In cases where these workers are inexperienced farmers, it is understandable if agricultural crop yields are low.
Agroforestry is already practiced by many African small farmers (Olofson, 1982). However, there is considerable agreement among scientists that it could, if practiced more widely, provide a solution to some of the problems experienced with fallow cultivation in conditions of rising population density and increasing land shortage (Vergara, 1981; Raintree, 1980). Indeed, this is the assumption behind much of the work of the International Council for Research in Agroforestry (ICRAF) in Nairobi. For example, both the International Institute of Tropical Agriculture and ICRAF are carrying out field trials with alley cropping of the fast-growing woody leguminous genus Leucaena (IITA: Hartmans, 1981; Okigbo, 1981. ICRAF: Raintree, 1980). Unfortunately, there is as yet little information on the acceptability of these techniques to fallow farmers, since these trials have been carried out in areas of permanent cultivation.
Work on the intensification of agriculture based on agroforestry techniques is particularly promising because it emphasizes the close relationship between the type of agricultural improvement on the one hand and the availability of labour and intensity of land use on the other. Below is a hypothetical progression from planted fallow to intensive multistorey intercropping suitable for maintaining or improving per caput yields on a fixed land base under conditions of population pressure and land shortage:
· In the initial stage, as land pressure converts long-fallow farmers into short-fallow farmers, the use of appropriate tree legumes as planted fallows can increase and sustain the productivity of the land at fairly low labour costs.
· Through the initial planting of fallow trees in appropriately spaced rows, the stage is set for the next phase of intensification, in which progressively shorter rotations eventually result in permanent cultivation in the alleys between the pruned hedgerows of vigorously coppicing trees.
· In the final, increasingly labour intensive stages, the installed green manure "fertilizer factories" can be maintained in place while additional upper-storey trees and intercropping practices are introduced to accommodate higher population densities; in other words, multistorey intercropping. This final phase offers the closest approximation to the characteristics of the tropical forests and is not at all a new idea. The innovation here is the incorporation of soil-improving economic tree legumes into the upper storey of the system and the choice of species with light or seasonal canopies which permit the system to extend to field crops. Raintree (1980) lists a number of species suitable for this purpose.
If the motivation exists, there is no reason why the scheme of intensification outlined here cannot be run "ahead of itself" to generate higher incomes for industrious rural families well in advance of population pressured necessity. The scheme likewise allows great flexibility in the combination of elements from different "stages" for the simultaneous production of optimal products for particular localities (Raintree, 1980, 1983).
Agroforestry is just one of many ways in which farmers faced both with the need to produce more food and with increasing scarcity of land and deteriorating soil can transform shifting cultivation into a more positive and productive cropping system which can be practiced in full harmony with the natural surroundings and the needs of their human occupants. Any changes should take into account local physical or socioeconomic constraints. There is need for more dialogue with farmers so that both foresters and agriculturists can learn from their considerable local experience, and so that alternatives proposed in particular areas may be well adapted to the particular needs and skills of the local inhabitants.
APPLETON, N.S. 1982. Some considerations for agro-silviculture development in the shifting cultivation areas of Liberia. Paper presented to the FAO/University of Ibadan Workshop on Shifting Cultivation, 4-11 July.
BALL, J.B. & UMEH, L.I. 1981. Development trends in taungya systems in the moist lowland forest zone of Nigeria between 1975 and 1980. Paper presented at the Workshop on Agroforestry in the African Humid Tropics, University of Ibadan. Ibadan, Nigeria, Federal Department of Forestry.
BOSERUP, E. 1965. The conditions of agricultural growth. London, Allen & Unwin.
BROOKMAN-AMISSAH, J. 1978. Agrisilviculture for production of wood and food crops in Ghana. Paper presented at the 8th World Forestry Congress, Jakarta.
DE ROUW, A. 1979. La culture traditionnelle dans le sud-ouest de la Côte-d'Ivoire (région de Tai): le système Oubi confronté aux pratiques agricoles des Baoulés immigrés. Abidjan, Centre d'Adiopodoumé, Office de la recherche scientifique et technique outre-mer.
EARL, D.E. 1982. Rainforest conversion: when cheap may be costly. In World wood, p. 22-23.
FAO. 1956. L'agriculture nomade, vol. I. Congo belge, Côte-d'Ivoire. FAO Forestry Development Paper N° 9. Rome.
FAO. 1984. Institutional aspects of shifting cultivation in Africa. FAO Human Resources, Institutions and Agrarian Reform Division. Based on work by Dr M. Tiffen. Rome.
FAO/UNIVERSITY OF IBADAN. 1982. Recommendations arising from the Workshop on Shifting Cultivation and Extension. Rome.
FAO/WORLD BANK. 1982. Sierra Leone: Forestry Development Project preparation report. Rome.
GRINNELL, H.R. 1975. A study of agrisilviculture potential in West Africa. Ottawa, International Development Research Centre.
GROSSMAN, D. 1974. The affect of migratory tenant farming on food production in northern Iboland, Nigeria. Natn. geogr. J. of India, 20 (4).
HARTMANS, E.H. 1981. Land development and management in tropical Africa. Ibadan, Nigeria, International Institute of Tropical Agriculture.
HILL, P. 1963. Migrant cocoa farmers of southern Ghana. Cambridge University Press.
JEAN, S. 1975. Les jachères en Afrique tropicale. Interprétation technique et foncière. Mémoire de l'Institut d'ethnologie N° 14. Paris, Musée de l'homme.
JURION, F. & HENRY, J. 1967. De l'agriculture itinérante de l'agriculture intensifiée. Brussels, Institut national pour l'étude agronomique du Congo.
LASSAILLY-JACOB, V. 1982. Logique des agricultures itinérantes et cycliques: la reconstitution du sol par la jachère suit son exploitation par les cultures. In H. Dupriez. Paysans d'Afrique noire. Paris, Edition l'Harmattan.
LASSAILLY-JACOB, V. 1983. La charge de population en question: colonisation planifiée des rives du lac de Kossou en Côte-d'Ivoire.
LAWTON, R.M. 1982. National resources of miombo woodland and recent changes in agricultural and land-use practices. Forest Ecology and Management, 4: 284-97.
NYE, P.H. & GREENLAND, D.J. 1960. The soil under shifting cultivation. Farnham Royal, UK, Commonwealth Agriculture Bureaux.
OKIGBO, B.N. 1981. Alternatives to shifting cultivation. Ceres (FAO), 15 (6): 41-45. Rome.
OLAWOYE, O.O. 1975. The agri-silvicultural system in Nigeria. Commonw. For. Rev., 54 (3/4): 229-236.
OLOFSON, H. 1982. An anthropological approach to social forestry: the study of indigenous agroforestry systems. Paper presented to the Monthly Forum in Social Forestry of the Bureau of Forest Development, Asian Institute of Tourism, Quezon City, Philippines.
RAINTREE, J.B. 1980. Conservation farming with soil improving legumes: a farming systems approach to tropical agroforestry. IITA Agric. Econ. Discussion Paper 9/80.
RAINTREE, J.B. 1981. Conservation farming with multipurpose tree legumes: an underdeveloped branch of tropical agroforestry research. In L. Buck, ed. Proceedings of the Kenya National Seminar on Agroforestry (12-22 Nov. 1980). Nairobi, ICRAF.
RAINTREE, J.B. 1983. Landuse and labour intensity: factors affecting the adaptability of conservation farming practices under conditions of population pressure. Paper presented for the Workshop in Conservation Farming, Colombo, 17-23 Jan. 1983. Nairobi, ICRAF.
RICHARDS, A.I. 1939. Land labour and diet in Northern Rhodesia: an economic study of the Bemba tribe. Oxford University Press, for the International Institute of African Languages and Cultures.
RICHARDS, P. 1977. Ideas, environment and agricultural changes: a case study from western Nigeria. Ph. D. thesis, University of London.
RUTHENBERG, H. 1980. Farming systems in the tropics. 3rd. (also 2nd ed., 1976). Oxford, Clarendon Press (see especially chap. 3, "Shifting cultivation systems").
UNITED NATIONS UNIVERSITY. 1982. Taungya practices in Togo, by O. Nadjombe. In L.H. MacDonald, ed. Agro-forestry in the African Humid Tropics. Tokyo.
VERGARA, N.T. 1981. Integral agroforestry: a potential strategy for stabilizing shifting cultivation and sustaining productivity of the natural environment. Honolulu, Hawaii, East-West Center, Environment and Policy Institute.
VERMEER, D.E. 1970. Population pressure and crop rotational changes among the Tiv of Nigeria. Ann. Ass. Amer. Geogr., 60 (2): 299-314.
FAO - FOREST RESOURCES/RESSOURCES FORESTIÈRES/RECURSOS FORESTALES
Subscribers to Unasylva will find enclosed in this issue a new FAO document, entitled Forest resources 1980. This offers the most accurate and up-to-date data currently available internationally on the world's resources (as of July 1985). The source of the data is an FAO assessment of tropical forests and the FAO/Economic Commission for Europe (ECE) assessment of forests in ECE member countries. Figures are given by region and by country for total coniferous and non-coniferous forest; for closed forest and other wooded land area; for total land area occupied by forest; and for fallows and shrubs not included in the forest area. Included are 26 four-colour, computer-generated maps and a brief descriptive text in three languages (English, French and Spanish). Figures are given for forest renewal for all countries and for loss of forest in the tropical countries. The document has been prepared in conjunction with FAO's International Year of the Forest.
Readers who have received this copy of Unasylva other than by subscription and who would like a copy of the document, and those interested in a copy with slides, may write to:
Mr Philip Wardle, Senior Forestry Economist,
Policy and Planning Service, Forestry Department,
Via delle Terme di Caracalla, 00100 Rome, Italy