0614-B1
Ndjomguem Tuma Clement-Piere [1]
The Forest of the Congo Basin covers approximately 2.8 million km², an area about one third the size of the largest contiguous block of tropical forest after the Amazon. These forests contain a diversity of plants and animals unmatched in Africa, and continue to provide food, shelter and income to 25 to 30 million people.
The Forest of the Congo Basin has over millennia, expanded, contracted and changed in species composition in response to climatic variability and disturbance by humans. In the last 20 years as a result of globalization of market economics and growth in demand, the scale and rate of exploitation of wood and non-wood forest products has expanded faster than at any other time in history, and use of forest resources is approaching or exceeding sustainable thresholds in many locations across the Congo Basin. Ignoring ecological constraints can lead to the gradual elimination of a species from the forest.
The forest of the Congo Basin cover approximately 2,8 millions Km2; it constitute the second largest contiguous block of tropical forest after the Amazon (BSP, 1993). These forests contain a diversity of plants and animals unmatched in Africa, an continue to provide food, shelter and income to 25-30 million people (Buhuchet, 1995).
The forest of the Congo Basin have millennia, expanded, contracted and changed in species composition in response to climatic variability and disturbance by humans (Oslisly, 1995; Oslisly, 1998). In last 20 years, as a result of globalization of market economies and growth in demand, the scale and rate of exploitation of wood and non-wood forest products (NWFPS) has expanded faster than at any other time in history, and use of forest resources is approaching or exceeding sustainable thresholds in many locations across the Congo Basin. Over-exploitation and eventual disappearance of wood and NWFPS are of both local and global concern, because when a plant or animal goes locally extinct, it:
- Can no longer contribute to the diet or economy of forest families and,
- Risks the irreplacement loss of species and genetic biodiversity that may contribute significantly to forest ecosystem production and resilience.
Given the number of products used by humans that originate from forest (wood products- Logs, sawn wood, poles, fuel wood, charcoal, and non-wood products, bark, roots, tubers, corms, leaves, flowers, seeds, fruits, sap, resins, honey, fungi and animal products, that include everything from termite to elephants); the enormous range of domestic and commercial uses of these products; and the complexity of the pathways along which forest products travel from producer to consumer.
Excluding bush meat hunting, trophy hunting and the live animal trade is contentious as some would argue that in terms of value to local economics and immediate threat to biodiversity conservation trade in animal is a key issue.
At present it is generally recognized that NWFPs and woods play an important role for subsistence and cash income for local people. The awareness is growing that effective conservation and management of NWFP and wood resources should be included in natural forest management in order to meet the present and future needs of local populations. Moreover, the development of commercial extraction of wood and NWFPs is often seen as a way to ensure forest conservation whilst improving rural peoples' living standards. (Ros-Tonen, Dijkman and Lammerts Van Bueren, 1995).
Wood and NWFPs are big business now, and numerous efforts are currently under way to promote the exploitation of these valuable and highly-publicated resources. Much attention has often focused on the economic ride of things, e.g. developing markets for different products, implementing local processing and value-added strategies and ensuing the equitable distribution of income generated.Social issues such as securing land tenure or usufruct right for collector groups have also played a prominent role. It is some what surprising, however, that the ecological factors associated with the exploitation of NWFPs and woods products have only rarely been addressed. Maintaining a reliable income flow over time from a Congo Basin forest requires that the forest resources upon which this flow is based be maintained as well.
If these resources are depleted through over-exploitation, destructive harvesting, or poor management, no new market, cottage industry or land- tenure system will make very much difference. In the long term, ecology is arguably the bottom line for sustainability.
A major problem with,
Human cultures have developed a variety of different way to use forest vegetation. Each form of land-use carries with it a particular unite of ecological costs. Perhaps the most intensive and costly way to use a forest is to cut it down, burn it, and plant something else (e.g. timber tree, agricultural crops, pasture grasses) on the site. The ecological impacts of forest conversion are immediate, highly visible and, in most cases, highly severe, current research the Congo Basic forest suggests that the most important of these impacts include:
The loss of biomass and species diversity.
The release of C02 and other green house gases.
Disruption of nutrient and hydrological cycles.
Soil loss through erosion.
Increased local temperatures and decreased local rainfall.
Another common use of Congo Basin forest is to selectively cut and remove the desirable timber trees. Although certainly less damaging than total forest conversion, selective logging is also know to produce a number of ecological repercussions. The most conspicuous of these are:
Loss of some plant and animal species
Damage to residual tree
Soil loss through erosion
Loss of nutrients through stem removal
Change in forest structure and increase in light level.
A major problem with selective logging in the Congo Basin forests is that the crowns of many large canopy trees are lashed to those of their neighbours by a profusion of vines, lianas and climbers. When selected timber trees are felled, other canopy species are pulled down and the whole woody mass crashes through the lower canopy, snapping tree boles, breaking branches and flattening a considerable proportion of the forest under story. Harvesting even a small number of stems can destroy up to 55% of the residual stand and seriously damage an additional 3% to 6% of the standing tress (Burgess, 1971; Johns, 1988). Associated impacts include soil compaction, decreased infiltration of water, increased rate of soil loss from erosion, disruption of local animal populations, increased susceptibility to fire (uhl et al., 1988); and nutrient loss from the removal of saw logs. Commercial tree felling produces a notable impact on a forest ecosystem, and the physical evidence of this disturbance is immediately apparent and persists in the form of logging roads, skid trails, and scattered stumps for many years.
A final form of Congo Basin forests use is the selective harvest of fruits, nuts, latex and other non-wood resources. Although relatively benign when compared with forest clearing and selective logging, this activity also produces number of ecological impacts including:
Gradual reduction in the vigour of harvest plants
Decrease in rate of seedling establishing of harvest species
Potential disruption of local animal populations
Nutrient loss from harvested material
At first glance, there impacts seem insignificant. The harvest of non-wood forest products does not necessarily kill the plant, compact the soil, increase erosion, or cause a notable change in the structure and function of the forest. A forest exploited for non-wood resources, unlike a logged-over forest, maintains the appearance of being undisturbed. It is easy to overlook the subtle impacts of NWFP harvest and to assume a priority that this activity is something that can be done repeatedly, year after year, on a sustainable basis. This ubiquitous idea, or some variant of it, has appeared in books, scientific papers, conference proceedings, grant proposals, magazine articles ... etc. Unfortunately, in the great majority of cases, this assumption is potently incorrect.
From a Commercial stand point, the high diversity of Congo Basin forest is a mixed blessing. On the one hand, forests containing a large number of different species usually contain an equally diverse assortment of useful plant species i.e. species richness and resource richness are usually correlated. The great interest in Congo Basin Forests as an undiscovered source of new food, materials, and medicines is largely in response to the magnitude of the species pool in these ecosystems. Unfortunately, an additional correlate to high species diversity is that the individuals of a given species usually occur at very low densities. There is a limit to the total number of trees that can be packed into a hectare of forest. If you have a large number of species, each species can only be represented by a few individuals. Although there may be an abundance of resources in Congo Basin Forests, most of them are scattered throughout the forest at extremely low densities. Low-density resources are difficult for collectors to locate, they require length travel time, produce a low- yield per unit area, and they are extremely susceptible to over -exploitation.
A second characteristic of trees that represents a stumbling block to sustainability concerns the way that they move their pollen and disperse their seeds. The low density and scattered distribution of individual in many Congo Basin forest trees populations greatly complicates the process of pollination. Given that the distance between co-specific individuals may be greater than 100 meters in some case, moving pollen from the flowers of one tree to another can be difficult proposition.
Many of these trees have overcome this problem by coevolving relationship with a verity of animals, ranging from tiny trips and midges to bees and large bats, that act as long- distance pollen vectors. These relationship can be quite specific, with one type of insect being soppy responsible for pollinating the flowers of a particular species or even genus, of forest tree (e.g. Wiebes, 1979). The use of biotic vectors to transfer pollen is apparently the norm in Congo Basin forest. Animals also play a very important role in dispersing the seeds produced by trees.
These animals may either remove fruit and seeds directly from the tree (primary disperses).
The production of fruit, seeds, and seedlings in Congo Basin forest necessarily involves the collaboration of animals. Although it is very easy to overlook this fact, or to view forest animals solely as pest that damage or consume large quantities of fruit, sustainable resource in Congo Basin forests ultimately depends on the continual availability of pollination and seed dispersers. In simple terms, no pollination means no fruits, no fruit and/or no disperses means no established seedlings, and no established seedlings means no next generation, no products, no profits and importantly, no sustainability.
A final characteristic of many Congo Basin tree species is that they have very difficult time recruiting new seedling into their populations. Even given abundant pollination, fruit set, and dispersal, there is still a very, very small probability that a seedling will become successfully established in the forest, The seed must avoid being eaten, it must encounter the appropriate light, soil moisture and nutrient conditions for germination, and it must be able to germinate and grow faster than the seeds of all other species that are competing to establish themselves on that microsite. The young seedling must then stay free of pathogen, be able to recuperate from the damage caused by herbivores, avoid falling branches and other hazards, and continue to photosynthesise and push its way upward into the forest canopy. Not surprisingly, mortality during the early stage of the life cycle of a Congo Basin plant is extremely high.
Given the low density of Congo Basin forest species, their reliance on animals for reproduction, and the difficulty experienced in establishing their seedlings, the harvest of any type of plant tissue will necessity have an effect on the species involved. The delicate ecological balance maintained in a Congo Basin forest is easily disrupted by human intervention, and extractive activities that at first glance appear very benign can later have a severe impact on the structure and dynamics of forest tree populations. This impact may not be immediately visible to the untrained eye, but it is definitely occurring.
In general, the ecological impact of wood and NWFPs utilization depends on the nature and intensity of harvesting and the particular species and type of resource under exploitation.
Sporadic collection of a few fruits or the periodic harvesting of leaves for cordage may have little impact on the long-term stability of a tree population. Intensive annual harvesting of a valuable market fruit or oil seed, on the other hand, can gradually eliminate a species from the forest. The felling of large adult tree can produce a similar ecological result in a much shorter time period- A large number of non-wood forest resource are actually harvested destructively: prunus Africana trees in Cameroon are felled or completely stripped and girdled to harvest the bark tissue (Cunninghan and Mbenkun, 1993). There are numerous other examples of forest species that are killed or totally wounded by the harvest of non-wood products. First it is assumed that all of the seeds left in the forest are positioned in precisely that right spot for germination and early growth. Second, there is always the possibility that the fruit and seeds left in the forest will experience a rate of mortality that is higher than 95%. Commercial collectors, in effect, are competitors with forest frugivores, and their activities reduce the total supply of food resource available. In response to the reduced abundance of fruit and seeds, frugivores might be forced to increase their foraging to obtain sufficient food. The net result would be an increase in the total percentage of seeds destroyed.
All of their factors interact in a synergistic fashion to inhibit the recruitment of new individuals into a plant population. Over time, this lack of recruitment will alter the size- class distribution of the population being harvested. If commercial collection continues uncontrolled, the harvest species can be gradually eliminate from the forest. In
Addition to its impact on seedling establishment and population structure, the collection of non-wood forest products can also affect the genetic composition of the plant population being exploited (peters, 1990c). A population of forest fruit tree, for example, will usually contain several individuals that product large succulent fruits, a great number of individual that produce fruit of intermediate size or quality, and a few individual that produce fruits that, from a commercial standpoint, are inferior because of small size, bitter taste, or poor appearance.
If this population is subjected to intensive fruit collection, the << inferior >>tree will be the ones whose fruit and seeds are left in the forest to regenerate. Over time, the selective removal of only best fruit types will result in a population dominated by tree of marginal economic value.
It seems unlikely that the unfettered interaction of markets, commercial- collectors, in Congo Basin forest species will automatically produce a sustainable form of resource use. Achieving this objective will require more than blind faith in the productive capacity of Congo Basin forest trees, an unwavering trust in a free market system, and the unquestioned assumption that local collector groups instinctually hold the goals of forest conservation above any desire for personal economic gain. Sustainable Exploitation of woods and NWFPs will require a concerted management effort by all of the party involved. It will require careful selection of the species, resource, and sites.
It will require controlled harvesting and periodic monitoring of the regeneration and growth of the species being exploited. More than anything, however, it will require a
Great appreciation of the fact that ecology and management are the cornerstones of sustainable resource use. One of the most essential ingredients required to achieve a sustainable level of resource use is information. It means information about the population
Structure and productivity of these resources information about the density within the forest and information about the ecological impact of differing harvest levels.
Ashton, P.H. 1984. Biosystematics of tropical woody plants: A problem of rare species, pp. 497-518 in W.F. Grant(ed), Plant Biosystematics. New York, Academic Press.
Bawa, K.S., S.H Bullock, D.R Perry, R.E Coville & M.H Grayum. 1985. Reproductive biology of tropical lowland rain forest trees. II. Pollination systems. American Journal of Botany 72:346-356.
Brown, F.I, L.A. Martineli, W.W. Thomas, M.Z Moreira, C.A Cid Ferreira & R.A. Victoria. 1995. Uncertainty in the biomass of Amazonian forests: An example from Rondonia, Brazil. Forest Ecology and Management 75: 175-189.
Burgess, P.F. 1971. Effect of logging on hill Dipterocarp forest. Malaysian nature Journal 24:231-237.
Campbell, D.G., D.C. Dally, G.T Prance & U.N Maciel. 1986. Quantitative ecological inventory of terra firme and verzea tropical forests on the Rio Xingu, Brazilian Amazon. Brittonia 38.369-393.
Croat, T.B. 1978, Flora of Barro Colorado Island. La Jolla, Stanford University Press.
Cunningham, A.B. & F.T Mbenkum. 1993. Sustainability of harvesting Pruns africana bark in Cameroon: A medicinal plant in international trade. People and Plants Working Papers No. 2. UNESCO.
Dransfield, J. & N.Manokaran. 1994. Rattans: Plant resources of South-East Asia No. 6 PROSEA, Bogor.
Faber-Lanendoen, D & A.H Gentry. 1991. The structure and diversity of rainforests at Bajo Calima, Choco Region, western Colombia, Biotropica 23:2-11.
Gentry, A.H. 1982. Patterns of neotropical plant species diversity. Evolutionary Biology 15:1-84.
Gentry, A.H 1988. Tree species richness of upper Amazonian Forests, Proceedings of the National Academy of Sciences 85:156-159.
Gianno, R. 1990, Semelai culture and resin technology. Connecticut Academy of Arts and Sciences.
Jessup, T.C & N.L. Peluso, 1986. Minor forest products as common property resources in East Kalimantan, Indonesia. Common Property Resource Management, National Academy Press.
Johns, A.D. 1988. Effects of "selective" timber extraction on rain forest structure and composition and some consequences for frugivores and folivores. Biotropica 20:31-37.
Jordan, C.F 1987. Amazonian rain forests: Disturbance and recovery, New York, Springer-Verlag.
Kartawinata, K.R. Abdulhadi & T. Partomihardjo. 1981. Composition and structure of lowland Dipterocarp forest at Wanariset, East Kalimantan. Malayan Forester 44:397.
Keller, M., D.J. Jacob, S.C. Wofsy & R.C Hariss. 1991. Effects of tropical deforestation on global and regional atmosphereic chemistry. Climatic Change 19:139-158.
Lang, G.E. & D.H. Knight. 1983. Tree growth, mortality, recruitment, and canopy gap formation during a 10-year period in a tropical moist forest. Ecology 64:1075-1080.
Manokaran, N. & K.M Kochummen, 1987. Recruitment, growth and mortality of tree species in a lowland dipterocarp froest in Peninsula Malaysia. Journal of Tropical Ecology 3:315-330
Peters, C.M 1989, Reproduction, growth, and the population dynamics of Brostimum alicastrum Sw. in a moist tropical forest of central Vercacruz Mexico. Ph. D. dissertation, Yale University, New Haven.
Peters. C.M 1990a. Plant demography and the management of tropical forest resources: A case study of Brosimum alicastrum in Mexico. Pp. 265-272 In: A. Gomez-Pompa, T.C. Whitmore, and M. Hadley (eds.), Rain Forest Regeneration and Management, Cambridge University Press.
Peters, C.M 1990b. Population ecology and management of forest fruit trees. In Peruvian Amazonia, pp. 86-98. In A.B Anderson (ed). Alternatives to deforestation: Steps toward sustainable use of Amazon rain forest, Columbia University Press.
Peters, C.M. 1990c. Plenty of fruit but no free lunch. Garden 14:8-13.
Peters, C.M. 1994. Sustainable harvest of non-timber plant resources in tropical moist forest: an ecological primer. Washington, Biodiveristy Support Program.
Peters, C.M., M.J, Balick, F. Kahn & A.B Anderson. 1989. Oligarchic forests of economic plants in Amazonia; Utilisation and conservation of an important tropical resource. Conservation Biology 3:341-349.
Procter, J., J.M Anderson, P. Chai & H.W Vallack. 1983. Ecological studies in four contrasting lowland rain forests in Gunung Mulu National Park, Sarawak, Journal of Ecolocy 71:237-260
Reitsma, J.M 1988. Vegetation Forestiere du Gabon. Tropenbos Tech. Series 1:1-42
Shukla, J., C.A. Nobre & P. Sellers. 1990 Amazon deforestation and climate change. Science 247:1322-1325.
Sunderland. T.C.H., C.J Ros, J.A. Comiskey & A. Njiamnshi. 1997. The vegetation of the Campo Faunal Reserve and the Ejagham Forest Reserve. Cameroon International Cooperative Biodiversity Group/Smithsonian Institution - Man and the Biosphere program.
Turner, I.M 1990. The seedling survivorship and growth of three Shorea species in a Malaysian tropical rain forest. Journal of Tropical Ecology 6:469-478.
Uhl, C., J.B Kauffman & D.L Cummings. 1988. Fire in the Venezuelan Amazon. 2: Environmental conditions necessary for forest fires in the evergreen rainforest of Venezuela, Oikos 53:176-184.
Valencai, R. H. Balslev & G. Paz y MinoC. 1994. High tree alpha-diversity in Amazonian Ecuador. Biodiversity and Conservation 3:21-28.
Vazquez, R. & A.H Gentry. 1989. Use and mis-use of forest-harvested fruits in the Iquitos area. Conservation Biology 3:350-361.
Wiebes, J.T. 1979. Coevolution of figs and their insect pollinators. Annual Review of Ecology and Systematics 10:1-12.
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