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Les orphelins de la forêt

Stéphanie Carrière


Texte intégral

Orphans of the forest

Farmers’ practices and forest ecology (the Ntumu of southern Cameroon)

1The traditional populations of swidden farmers scattered in the forests of central Africa combine shifting slash and burn cultivation and hunting, fishing and gathering. As Professor Bahuchet says, “there is no virgin forest” as people have lived in the forests for so long that they have changed their structure and composition. Many of these societies lived in balance harmony with their environments, but the changes today are rapid and often irreversible.

2The study was conducted for preventive purposes at a time when the Ntumu in southern Cameroon were fairly isolated from outside influences. It is true that the balances between populations and the forest environment were precarious at the end of the 1990s, but traditional farming practices contributed to the sustainability of the System through the maintaining of a long period of fallow and hence management of the forest environment that was appropriate for these regions. Thanks to these practices, farmers had, over periods of thousands of years, fashioned and changed the equatorial forest, often to their advantage, by selecting species useful to man. Analysis of a farming System typical of the swidden farmers of central Africa (the Ntumu of southern Cameroon) led to the identification of ancestral farming practices that contribute to the maintaining of a balance between the populations and the environment. These practices were studied from the ecological and ethnoecological angles. Selective felling, that is to say the sparing or protecting of certain trees when fields are cleared has often been observed in swidden farming populations in the tropics. However, few in-depth studies have been devoted to this practice and, in particular, to the varied, complex reasons for its implementation. Likewise, few scientists in ecology have devoted themselves to understanding the influence of isolated trees in fields on forest regeneration. The research conducted within the framework of the programme The Future of Tropical Rainforest Peoples (FTRP) makes use of empirical knowledge of nature and the ecological processes learned by the forest populations in order to contribute to the protection of equatorial forest.

3The Ntumu (their language belongs to the large Beti language group) are scattered in the southern Cameroon equatorial forest but are also found in northern Gabon and Equatorial Guinea. The villages used to shift but then became settled near roads during colonisation. A large proportion of the peoples in southern Cameroon are grouped in small village/streets. The populations practice subsistence activities such as shifting slash and burn farming, hunting, fishing and gathering in forest areas around the villages. Cocoa, a cash crop, is grown in complex, multi-purpose agroforests. The crop was introduced by German colonists and then developed during French colonisation.

4The Ntumu have several kinds of food crop fields, each characterised by a dominant crop. Squash generally precedes groundnut, in smaller fields. This is followed by starch food crops intercropped in the same field—cassava, plantain, sweet potato, yam and taro. The Ntumu more rarely grow rice in low-lying land or flooded raphia palm zones. The diversity of intercropping in both time and space is a characteristic of this multiple food crop farming. Clearing is performed twice a year for groundnut and once a year or once every two years for squash. Fields are created frequently and so populations have not only varied food crops but also crops that are staggered in time. The time-lag means that families can always obtain food supplies. This diversification strategy also reduces the risks resulting from climatic, economic or social uncertainties (weddings, deaths, religious festivals, etc.). Always linked with agriculture, seasonal occupations such as hunting, fishing and gathering improve the quality of the diet and of life. Finally, the time spent on cocoa growing does not hinder the progress of subsistence activities because it is evenly distributed in the annual calendar. Although the cocoa agroforests are comparatively recent, they reflect to a considerable extent Ntumu farming ‘culture’ through their multipurpose nature and the fundamental rôle of the tree in both their economic and ecological management.

5Ntumu slash and burn farming is based on the mineralisation by fire of the plant and animal organic substances in forest that has been felled and left to dry. Clearing and felling are necessary for growing crops. Fertility after burning enables farmers to grow two or three successive cycles before starting to abandon the land (fallow period). For Ntumu farmers, this phase is necessary for the reconstitution of the fertility of the environment before starting a fresh cycle of crops. The regeneration of woody vegetation is a sine qua non for the restoration of soil fertility. Agricultural practices such as selective felling that favour the effectiveness of fallow have been selected by generations of traditional swidden farmers.

6Selective felling in food crop fields consists of sparing the trees chosen and protected by the farmer and his wife to form an integral part of the future system formed by the ‘crop-fallow’ sequence. For the Ntumu, this practice is systematic and obligatory.

7In Ntumu society, the protected varieties have a social value (symbolic and ritual), a cultural value (for medicine, food, hunting, fishing, gathering or material uses in building, basket making, etc.) or agricultural, ecological and economic value. For the Ntumu, the protected trees in the fields are the ‘orphans of the forest’. Indeed, after the felling of the forest, an essentially warlike act, the Ntumu consider that these trees have lost a large part of their family and naturally become orphans of the forest. This status ends when the land is left fallow because, thanks to new forest regrowth, these trees will no longer be alone. It is true that some ‘undesired’ kinds of tree are also left in the fields through shortage of time or labour for felling them, but most of the orphan trees are selected before felling opérations. In tact, their presence influence the choice of the plot to be cleared. For the Ntumu, some kinds of trees are indicators of the fertility of the environment. The density of protected trees in the fields can vary according to farming strategies. It depends on many social, cultural and ecological parameters. Finally, felling is the resuit of a compromise decided between the men and the women according to the responsibilities of each with regard to the crops concerned.

8Two main phenomena in ecology explain the presence of trees in the fields. The first concerns the improvement of the physico-chemical and soil conditions under and around the orphan trees. The second is related to a considerable increase in ‘seed rain’ beneath the trees, making them a favourite place for seed-dispersing animals. The latter would be reluctant to cross open spaces if there were no trees. The two processes work together to accelerate forest regeneration because the seeds deposited under the trees have ideal germination conditions. The facilitation phenomenon can spread around these cores of regenerations which coalesce with each other according to the predictive nucleation model and thus reconstitute forest cover more rapidly.

9The study conducted in southern Cameroon concerned protected trees and the nucleation phenomenon in order to assess their roles in the increase in seed rain, the improvement of physico-chemical conditions and hence the possible acceleration of forest regeneration. Indeed, seed rain is much greater and more diversified under the crowns of orphan trees than under the open sky where it is almost nonexistent. It is also greater near the trunk than under the crown. About a hundred species were counted among the seeds, most of which were dispersed by fruit-eating animals and a few dispersed by the wind. Furthermore, the seed rain contributed by animals increases under isolated trees that produce fleshy fruits. These fruits are thus particularly attractive for seed-dispersing animals. However, the number of seeds observed under trees that do not bear fleshy fruits leads to considering that the attraction mechanisms are less dichotomous. Indeed, other reasons might encourage birds to settle on isolated trees in the fields (nesting, song and courtship, protection, roosts, food other than fruits, etc.). Another component of the study also compared the dispersal of seeds under isolated trees with human activity. The seed rain resulting from animals decreased during periods of intense human activity, leading to thinking that the presence of farmers could frighten the animals. It is interesting to reposition this observation within the framework of forest succession. Indeed, post-agricultural regrowth begins precisely when human presence decreases (weeding ends but harvesting continues).

10The scattering of seeds in the fields to be recolonised is a decisive factor in the ecological process of post-cropping forest regeneration. While the orphan trees form favourite sites for the depositing of seeds thanks to the dropping of seed-dispersing animals, they are also ecologically favourable sites for the seedlings growing from tree seeds. Indeed, in fallows of different ages, trees varieties become established more easily under the orphan trees than in the open parts of the fallow. Symmetrically, herbaceous plants are more plentiful under the open sky than under the crowns of trees. The isolated trees in the fields play a primordial role in the plant regrowth, which in one case tends towards a combination of shrubs and in the other to a mainly herbaceous stratum. The installation of mainly herbaceous regrowth may cause the blockage of the woody plant succession. Furthermore, analysis of the basal area (biomass estimator) showed that isolated trees have a strong effect. The micro-climate under the trees thus enhances the regeneration of woody species. The results as a whole suggest that the presence of these trees and the shade that they make in the fields short-circuits the first phase of woody regeneration, that of the stratum of African Corkwood (M. cecropioides).

11With the Ntumu, selective felling seems to be well suited to an equatorial forest farming system whose sustainability is based to a great extent on the effectiveness of fallow, that is to say the regeneration of woody vegetation after cropping.

12At the scale of the landscape, farming and selective felling influence the dynamics of forest formations, especially through clearing and the selection of species ‘useful’ for man during felling. Indeed, forest dynamics are modified by the spread of pioneer and/or anthropophile varieties in the zones with the strongest human pressure, contributing to the creation of patches of secondarised forest in ‘primary’ forest blocks. These practices change forest species composition in different ways and concern varied time scales.

13The two phenomena intermingle because pioneer species are often the species protected and selected by African farmers. The increase in the density of certain tree species in forest blocks in which farming is intense or longstanding (since nearly 2000 BP) may have been determinant in the species composition of today’s forests. Studies show that anthropic action occurs in conjunction with climate. In the Ntem valley in southern Cameroon, human action has probably locally modified the species composition of the forest around the dwelling zones. Agricultural activity and the changes induced have repercussion on a regional scale through the gradual penetration of deciduous species typical of post-farming regrowth in an original forest block consisting of evergreen species. This phenomenon gives birth to a forest mosaic consisting of evergreen forest blocks and other semi-deciduous blocks, contributing to increasing ecosystem diversity at the regional scale.

14Both the protection of trees in the fields and the slash and burn farming System show the adaptation of traditional swidden farmer societies to their environment. In the recent millenniums, tropical forest peoples have thus contributed to the enriching of their environment with species useful for their survival. There are many examples of adaptation of exploitation modes in the forest environment.

15Today, these traditional empirical practices such as selective felling could be used and updated by players in protection of the environment and development.

© IRD Éditions, 2003

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