Cultural and Ecological Survival in the Ituri Forest
Since the 1970s research conducted in the Ituri region of northeastern Zaire has documented the importance of climax tropical moist forest to the foraging practices of Mbuti hunter-gatherers. The forest is a major source of dietarily important ungulates and preserves of obligate species such as the unique and endemic forest giraffe (okapi).
Given the importance of this resource to the Ituri's indigenous populations, it is appalling that so little is known about the extent and location of mixed dominant climax forest remaining within the Ituri. No accurate, up-to-date forest inventories exist and even basic topographic maps to a scale of 1:100,000 or better are unavailable or outdated. Additionally, and perhaps more importantly, although forest within the Ituri region is being cleared annually by shifting cultivators, neither the number of horticulturalists inhabiting the Ituri nor the extent and consequences of forest clearing for agriculture are known.
Traditional Cultivation Disrupted
Traditional subsistence-level shifting cultivation requires that each farmer have access to large areas of land, because fields must remain under a forested fallow for 10 to 15 years to ensure nutrient replenishment and prevent resource degradation. Where population densities are low and ample land exists for clearing, shifting cultivation land use remains productive, maintains forest cover and permits sustained exploitation of the forest.
Prior to this century, access to forest suitable for cultivation was apparently not a limiting factor and mixed dominant climax forest was probably the predominant vegetation over much of the Ituri. However, recent changes in human demography within and surrounding the Ituri have placed a severe strain on traditional shifting cultivation practices. Since the 1940s swidden horticulturalists from dispersed villages within the forest interior have been moved to more permanent villages adjacent to the roadways that now traverse the Ituri. This enforced concentration of shifting cultivators has diminished the overall area of cultivable land readily accessible to each farmer, intensifying forest clearing and agricultural land use bordering the roads. Intensive roadside cultivation is clearly visible as lighter zones in a mosaic of two LANDSAT MSS satellite images of the Ituri region.
In addition, over the last few decades the Ituri has become a "settlement frontier" into which families from the rapidly growing, densely populated savannahs and highlands on the north and east are immigrating at an accelerated rate. These immigrants often bring land-use techniques which although applicable to the fertile volcanic soils of the eastern highlands, are incompatible with sustained exploitation of the forest. These more intensive cultivation practices result in the establishment of short duration grass fallows and consequent resource exhaustion.
Accurate Methods Needed to Monitor Forest Use
Changes in forest composition and vegetation community structure and patch size, which result from local changes in traditional land use practices, undoubtedly affect faunal species diversity and abundance - and consequently, Mbuti hunting practices and capture success.
Accurate and repeated monitoring of natural resources and land use at both local and regional scales is an essential step toward the preservation and sustained exploitation of the Ituri forest ecosystem. With this information, areas under greatest population pressure can be pinpointed and targeted for appropriate land use enhancement efforts. However, developing countries such as Zaire, which are under severe budget constraints and have at best an incomplete infrastructure, are faced with extraordinary problems in censuring their primarily rural citizens, assessing the type and extent of a given area's natural resources and determining on a local and regional level the extent, rate and impact of human land use practices.
Given the severe lack of funds in most developing countries and the accelerated rate of forest clearing within the world's tropical moist forests, traditional techniques often have become impractical for efficient monitoring of rapidly changing resources and land use. On the other hand, longitudinal field surveys of agricultural land use and forest regeneration, and extensive low-level, aerial photogrammetric resource mapping are prohibitively expensive and cannot, even under the best conditions, provide useful results for years. Thus, they are ill-suited to provide frequent reappraisals of the system. As a result, other fast, inexpensive, repeatable and accurate methods to monitor resource exploitation on a local and regional scale must be developed.
Simulation Models Helpful
To examine the impact of local changes in agricultural land use within the Ituri, a spatially accurate model was developed. The model, which simulates 45 years of forest-clearing, cultivation, vegetation regeneration and reclearing associated with four roadside villages, formalizes the field selection and forest clearing process associated with subsistence-level shifting cultivation. It also graphically displays changes in forest composition and distribution that result from population growth and altering traditional land use practices. For example, the model can show that under local population growth conditions, traditional land tenure systems collapse, villages are forced to relocate, the fallow period diminishes and secondary forest expands in area and patch size.
Similarly, model simulations clearly demonstrate that under population growth conditions Ituri climax forest is nearly completely cleared two to three km from the road. From this we can predict that climax forest species such as okapi will be extirpated from areas surrounding horticulturalists' settlements and that Mbuti hunter-gatherers will be forced to forage further afield or depend to a greater extent on exchanging field labor for cultivated crops. As population densities increase, the overall area of disturbed forest increases and the discrete patches of secondary vegetation begin to coalesce. This further reduces accessibility of climax forest and diminishes the likelihood of its regeneration.
Further refinement of the model to incorporate crop productivity, soil fertility and economic parameters would facilitate its use in testing procedures, such as agroforestry and alley cropping, that would help to mitigate the impact of population growth and intensification of shifting cultivation.
Satellite Imagery More Accurate
Although simulation models are useful for examining the detailed impact of changes in land use on a local scale, a means to monitor population densities and the rate and extent of forest clearing on a regional basis is still needed. Digital analyses of satellite imagery provide a rapid, comparatively inexpensive means to gather multitemporal "systematic, accurate, synoptic and up-to-date information" on natural resources and land use by shifting cultivators over large areas. While visual appraisal of LANDSAT MSS Band 6 imagery clearly shows the extent of intensive cultivation bordering roadways and surrounding population centers, digital analyses of multispectral imagery provide far greater detail and classification accuracy. Resolution as fine as 10m is now possible using SPOT satellite imagery.
Digital analyses also permit the preparation of accurate, up-to-date forest resource inventories and horticulturalist population censuses in a matter of months rather than years. Images from consecutive year or decades can be compared automatically to determine rates of clearing, population growth, expansion of grass fallows and areas under greatest exploitation pressure. Once land-cover/land-use classification schemes are developed for LANDSAT scenes of the Ituri, future surveys can be completed rapidly at even less cost, thus facilitating relatively frequent monitoring of the Ituri's resources.
Without the knowledge available through spatial land use models and digital processing of satellite imagery, it is unclear whether the Ituri forest's cultural and biological resources will be preserved in the absence of a concerted conservation policy, or whether the increased clearing by growing numbers of horticulturalists is altering the forest to such an extent that the survival of unique, endemic and dietarily significant fauna is endangered and the continued existence of one of the world's last remaining populations of hunter-gatherers is put in doubt.
A search by the author is currently under way for funding to enhance the land-use simulation model and to complete a satellite imagery-based forest-resource/land-use inventory of the Ituri forest. Such an inventory will provide vital data on human population densities, extent and rate of forest clearing by horticulturalists and the location and coverage of the Ituri's varied vegetation communities.
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