Forests Of Central Africa Research Articles

Farm and Forest in Central Africa: Toward an Integrated Rural Development Strategy

The authors explore three problems confronting scientists working in the central African humid forest zone and show their interconnectedness in the context of the sociopolitical history of the area. These problems emerge from different domains at different spatial scales: agricultural development, natural resource management, and landscape scale conservation. Land and livelihoods are severely constrained in central Africa. Agriculture is rarely remunerative: prices are low, technology limited, land rights contested, and labor scarce. People turn to “illegal” activities such as hunting, mining, pit-sawing, whisky brewing, and joining militias to make a living. Animal husbandry does not present a widely viable option. Land use planning at “landscape” scale is mooted to protect forests and save animals but it is not likely to address livelihood or governance concerns. Without clear legal frameworks and transparent processes, conflict and landgrabbing will result. Investors and planners should rather concentrate on crafting rural development strategies that reflect both the constraints and the comparative advantage of the central African humid forest zone. Above all, the authors argue, the days of carving out large areas of the forest for private concessions and government use, leaving small contested spaces for the locals, must come to an end.

Spatial pattern of central African rainforests can be predicted from average tree size

When considering all trees irrespective of their species, natural tropical rain forests typically exhibit spatial patterns that range from random to regular. The regularity is often interpreted as a footprint of tree competition. Using 23 permanent sample plots totalling 61 ha in the rain forests of central Africa, we characterized their spatial patterns and modelled those that exhibited regularity by a Strauss point process. This Strauss process is obtained as a Markov point process whose interaction function is an exponential function of a competition index commonly used in forestry. The parameter of this Strauss process characterizes the strength of competition. The 23 plots in central Africa differed in tree density and basal area, and could be discriminated depending on the type of spatial patterns: plots having a large basal area with respect to their density had a non regular pattern, whereas those having a small basal area with respect to their density had a regular pattern. For those plots that exhibited regularity, average tree size could be used to predict the strength of competition. The parameter of the Strauss process was significantly related to the average size by a linear relationship, such that competition decreases as average tree size increases. This relationship extrapolated to a null value of the Strauss parameter when average tree size reaches 32 cm in diameter. This relationship between average tree size and spatial pattern is a testable feature for future studies on the relationship between competition and spatial pattern in natural forests.

Recruitment dynamics of the grove-dominant tree Microberlinia bisulcata in African rain forest: extending the light response versus adult longevity trade-off concept

In groves of ectomycorrhizal caesalpiniaceous species in the Atlantic coastal forest of Central Africa the dominant tree Microberlinia bisulcata, which is shade-intolerant as a seedling but highly light-responding as a sapling, shows very limited regeneration. M. bisulcata saplings were mapped in an 82.5-ha plot at Korup and found to be located significantly far (>40 m) away from adults, a result confirmed by direct testing in a second 56-ha plot. Sapling growth over 6 years, the distribution of newly emerging seedlings around adults, recruitment of saplings in a large opening and the outward extent of seedlings at the grove edge were also investigated. Two processes appear to have been operating: (1) a very strong and consistent restriction of the very numerous seedlings establishing after masting close to adults, and (2) a strong but highly spatially variable promotion of distant survivors by increased light from the deaths of large trees of species other than M. bisulcata (which itself has very low mortality rate). This leads to an apparent escape-from-adults effect. To maintain saplings in the shade between multiple short periods of release ectomycorrhizal connections to other co-occurring caesalp species may enable a rachet-type mechanism. The recorded sapling dynamics currently contribute an essential part of the long-term cycling of the groves. M. bisulcata is an interesting example of an important group of tropical trees, particularly in Africa, which are both highly light-demanding when young yet capable also of forming very large forest emergents. To more comprehensively explain tropical tree responses, the case is made for adding a new dimension to the trade-off concept of early tree light-response versus adult longevity.

Counting elephants in Montane forests: some sources of error

AbstractThe dung count method is widely used to estimate elephant numbers in forests. It was developed in the lowland forests of Central Africa but it is also used in Montane forests in eastern Africa. Using data collected on Mount Kenya and computer simulations, this paper explores the following issues associated with dung surveys in Montane forests: High rainfall at 3000 m altitude on Mount Kenya was expected to accelerate dung pile decay but no significant difference was found between 3000 and 2500 m where less rain falls, possibly because high rainfall at 3000 m is counteracted by lower temperatures; Physical obstacles make it difficult to walk long, straight transects in Montane forests. Deviating from a straight line pushes the distribution of distance measurements from dung piles to the transect centre line (pdist) towards a negative exponential (NE), which complicates data analysis and may give inaccurate estimates. Using short transects largely alleviate this problem; Analysis of dung count simulations shows that the expected sightability curve of pdist pushes towards a NE with increasing numbers of obstacles blocking the view, even along perfectly straight transects; Extrapolating measured dung density to map area on Mount Kenya resulted in an underestimate of c. 13%. An unstratified correction of map area to ground area for Montane areas would be biased because of the strong tendency for elephants to avoid steeply sloping areas.

The past protecting the future

PurposeIn answer to the urgent need to adapt conservation strategies and approaches to climate change, the purpose of this paper is to locate the climatically stable forests in West and Central Africa and to assess whether they overlap with the existing network of protected areas and if not, to prioritize them for protection.Design/methodology/approachWith ongoing global warming, rain forest will survive where locally soil moisture content remains high compensating for the regional drought stress. As a proxy for a soil moisture‐driven model, rainfall >2,000 mm, altitude >500 m and strong relief (standard deviation in elevation data pixels) were overlapped in a GIS analysis to locate the climatically stable forest within the present continuous forest of Central Africa and within the degraded forest of West Africa. As a means of verification, the biodiversity was measured in and outside the identified areas in Gabon and Equatorial Guinea as high levels of biodiversity are related to the survival and stability of the forest in the past. Biodiversity was calculated (measured as Fisher‐α diversity) for all trees (dbh >5 cm) on 66 transects (200 × 5 m).FindingsThe forest areas identified as climatically stable in the GIS analysis showed a higher biodiversity than the forest outside these areas (student T‐test: P<0.000035, stable = 54.7 and unstable = 33.7), supporting the validity of the model. Mapping the results of the GIS query showed that most of the climatically stable forests in West and Central Africa are located outside the park systems, and that it is already too late to protect the climatically stable forest in West Africa as almost nothing is left of it.Originality/valueWedged in between large‐scale drought tolerant ecosystems the African rain forest is most vulnerable to global climate change. Knowing which parts are climatically stable and resilient helps to set and focus conservation priorities and efforts. This approach is a powerful tool which has helped to identify areas with a high‐conservation priority in Africa.

Estimating the stock recovery rate using matrix models

The stock recovery rate, that is the ratio of the exploitable wood stock at the end of a felling cycle over the exploitable wood stock at the beginning of this cycle, is a key parameter used in the management plans of the natural forests in central Africa. Estimating this rate requires a model of forest dynamics. Forest managers usually use a formula that is based on a simple model that assumes constant vital rates. A generalization of this formula is based on matrix models of population dynamics. The stock recovery rate at the end of the k th felling cycle can be simply computed using matrix models. The asymptotic stock recovery rate (that is the limit as k tends to infinity) is the asymptotic growth rate (that is the dominant eigenvalue) of a transition matrix that includes harvest. The estimate of the stock recovery rate can be completed by its confidence interval using bootstrap methods. When applied to sapelli ( Entandrophragma cylindricum, Meliaceae), a major timber species in central Africa, it turns out that a few thousands observations are required to estimate the stock recovery rate with an accuracy of at least 10%. The number of observations available on an experimental site in the Central African Republic does not permit to do better than an accuracy of about 45% at level 95%. This does not permit to conclude whether the asymptotic stock recovery rate is greater or less than one. As a conclusion, in management plans in central Africa, stock recovery rates should be given together with an indication of the variability of their estimate (standard error or confidence limits).

Changes in the chemical composition of the fruits ofGrewia coriaceaMast. during development and ripening.

Introduction. Grewia coriacea is a widespread plant species that occurs sponta- neously in tropical forests of Central Africa. It is one of the most important commercial spontaneous fruit crops in the Republic of Congo (Brazzaville), where it is harvested, sold and consumed on a rather large scale. However, similar to many other spontaneous products of the tropical rain forest in Africa, G. coriacea remains poorly studied and its nutritional potential is unknown. Because the fruit of G. coriacea is an important food for indigenous people in a large portion of the Congo River Basin, we studied the evolution of some compounds of this fruit starting from its fruit setting until its maturation. Materials and methods. The contents of various pigments (chlorophyll a and b, and carotenoids), and concentrations of soluble sugars, ascorbic acid and soluble proteins of the fruit pulp of G. coriacea were analyzed in the laboratory and they were followed during maturation. Results and discussion. The curves of evolution of the studied parameters followed some anti- cipated trends: increasing, decreasing or relative stability. Increasing applied to the carotenoids (3,0 mg·g -1 at the beginning of the fruit development up to 8.2 mg·g -1 at the end of its maturation), soluble sugars (9,9 µg·g -1 up to 75,4 µg·g -1 ), ascorbic acid (25 mg·100 g -1 up to 230 mg·100 g -1 ) and soluble proteins (7 µg·g -1 up to 40 µg·g -1 ). In contrast, the two chlorophyll pigments (chlo- rophyll a and b) showed an overall decreasing trend. Finally, the concentration of soluble proteins remained rather constant in the later stages, despite an initial increase in the early stage of deve- lopment. Conclusion. To our knowledge, these results are the first data published concerning the temporal changes in physico-chemical parameters of G. coriacea fruits in tropical Africa. The study shows that the studied fruits have high nutritional potentials, and that their ability to accumulate rather high levels of ascorbic acid could make them a potential source of vitamin C. Congo / Grewia coriacea / fruits / developmental stages / maturation / chemical composition / chlorophylls / carotenoids / sugars / ascorbic acid / proteins

Cassin's Hawk-Eagle Spizaetus africanus in Ndundulu Forest: a First Record for Tanzania, with Biogeographical Implications

A single adult Cassin's hawk-eagle Spizaetus africanus was sighted on five occasions over three years in a highland forest in the Udzungwa Mountains, the first ever record of this species in Tanzania. This discovery has potentially significant biogeographical implications, strengthening ancient links between the forests of the Udzungwa Mountains and the Guineo-Congolian forests of central Africa.

The work of the Central Africa Forests Commission (COMIFAC)

The work of the Central Africa Forests Commission (COMIFAC)

Integrating local and expert knowledge using participatory mapping and GIS to implement integrated forest management options in Akok, Cameroon

A spatially explicit understanding of local knowledge about land use and tenure is fundamental to developing and assessing sustainable management options for tropical forests in Central Africa. This paper presents a case study in the Humid Forest Zone of Cameroon to demonstrate the effectiveness of integrating participatory rural appraisal techniques with remote sensing and vegetation mapping in a geographic information system (GIS) environment. The full integration of biophysical and socio-cultural patterns within a GIS can identify spatial units important for ecosystem management and relate social institutions to land units across a variety of scales. Key words: landscape, forest-agriculture interface, tropical forest management, land tenure, participatory mapping, local knowledge

Cultivation by the Baka Hunter-Gatherers in the Tropical Rain Forest of Central Africa

The Baka in southeastern Cameroon are one of the Pygmy hunter-gatherer groups living in the tropical rain forest of central Africa. The Baka are said to have accepted cultivation with their own fields in the 1950s. Their cultivation is unplanned and haphazard, due to longer time lapse between labor investment and return for cultivation than for hunting-gathering. This differ- ence was one of the obstacles for adoption of cultivation with their own fields, and has made them receive produce from neighboring farmers in exchange for forest products or for farm work. The important factor for adoption of their own cultivation is that acquiring produce from the neighboring farmers became difficult due to change in relationship between some Baka and farmers. Colonial government policy also affected the Baka. The major crop of the Baka is plantain. Plantain as a crop requires little care or preservation for future planting and consumption, suited for the Baka cultivation. These factors probably promoted adoption of cultivation by the Baka.

Recovery of conservation values in Central African rain forest after logging and shifting cultivation

Secondary forests in Central Africa are increasing in importance for biodiversity conservation as old growth forests outside the few protected areas are disappearing rapidly. We examined vegetation recovery in a lowland rain forest area in Cameroon based on a detailed botanical survey of old growth forest and different-aged logging gaps (5-27 years) and shifting cultivation fields (10-60 years). Our analysis focuses on the long-term recovery of botanical conservation values by analysing trends in vegetation structure, species composition, species diversity and levels of endemism and rarity. In the total survey (4.25 ha), we recorded 834 species of which 23% were endemic to the Lower Guinea forest region. The proportion of endemic species was high in shrubs and low in herbs. Geographic range and (local) rarity were not significantly associated. The proportion of rare species (relative frequency ,10%) was high in woody climbers and low in trees. In logging gaps, recovery of all vegetation characteristics was relatively quick (5-14 years). Recovery in shifting cultivation sites took longer (30-60 years). Endemic species were found to be highly sensitive to shifting cultivation practices and even after 50-60 years the level of endemism was still significantly lower compared to old growth forest. The proportion of rare species was not significantly different between disturbed sites and old growth forest. We conclude that secondary forests can contribute to biodiversity conservation, e.g. as buffer zones around protected areas. However, this contribution should be assessed differently between land use types and widespread versus endemic species.

Morphological variability in the malaria vector, Anopheles moucheti, is not indicative of speciation: evidences from sympatric south Cameroon populations

Anopheles moucheti is a major human malaria vector in the vicinity of slow moving rivers in the tropical forests of Central Africa. Morphological variations in natural populations of A. moucheti led to the designation of three morphological forms named A. moucheti moucheti, A. moucheti nigeriensis and A. moucheti bervoetsi. Using allozyme markers, we investigated to which extent morphological and/or geographical populations of A. moucheti were genetically differentiated. Mosquitoes were collected from four villages 20–200 km distant apart in south Cameroon, where specimens from each morphological form were found in sympatry. All populations appeared highly homogenous across both morphological type and geographic location. Significant genetic differentiation was only observed between two locations 150 km apart ( F st=0.029; P=0.006), while no pairwise F st estimate between morphological forms reached statistical significance. Further evidence against any taxonomic value of this morphological classification was provided by direct observation of morphological variation within the progeny of field-collected females from all three types. Single female offspring always belonged to at least two morphologically recognised types and most often, a mixture of all three forms was observed. Our results therefore demonstrate that morphological variability within A. moucheti natural populations is not indicative of speciation. With this respect, restricted migration of individuals across river systems may be a more important factor in shaping population genetic structure of A. moucheti.

Impacts of simulated shifting cultivation on deforestation and the carbon stocks of the forests of central Africa

Research on shifting cultivation in the tropics has focused primarily on the issues of agricultural productivity and soil degradation. Few have attempted to quantify its impact on forest losses and the carbon cycle in the context of the global change debate. A simulation, which incorporated historic and projected rural population growth, was conducted to investigate the impacts of shifting cultivation on deforestation and the carbon stocks of the humid tropical forests of central Africa. The study demonstrated that in 1950, the central African forest region subjected to shifting cultivation was composed of 92% forest (including primary and secondary forests) and that in 1990 the forest cover had been reduced to 80% of the total simulated land area. The results of the simulation showed that with the current level of technology and consumptive habitats, shifting cultivation under projected rates of rural population growth would increase the annual rate of deforestation to 1.3%, converting 94% of the land area into cropland, fallow and secondary forests by 2050. At that time, only 40% of the potential above-ground biomass carbon (i.e., assuming all the simulated area is occupied by dense forests) will remain, compared to 85 and 74% in 1950 and 1990, respectively. The simulation suggests that there is a need for alternatives to shifting cultivation such as integration of cultivation intensification, fallow management and agroforestry if population pressure on the tropical forests of central Africa is to be alleviated. This preliminary regional study shows that modeling could provide an important tool to explore alternative scenarios of land use and to assist decision makers with forest management.

Human Responses to Changing Environments in Central Africa Between 40,000 and 12,000 B.P.

Reconstructions of the Equatorial forest in Central Africa fuel the debate on whether hunter-gatherers at the end of the Pleistocene were capable of living in or off the forest prior to the advent of agriculture. Their traces are rare and often reduced to their stone equipment. In an attempt to see to what extent technology and environmental exploitation are interrelated, all Central African sites dated between 40,000 and 12,000 B.P. are analyzed for their material culture, the environmental setting at the time of the occupation, and the exploitation of that environment. Although the evidence is still circumstantial, two large technological traditions have been recognized in Central Africa at the end of the Pleistocene, the Lupemban and microlithic industries, and both are associated with a variety of environments. This, in combination with a fragmented forest and concomitant increase of ecotone during the Last Glacial Maximum, would have enhanced rather than hampered human occupation in the area. It may be argued that the inherent flexibility and capability of exploiting a variety of environments enabled the hunter-gatherer communities to face and adapt to environmental changes regardless of stone technology.

Atelier sur la gestion de la faune sur les concessions de l’exploitation forestiere d’ Afrique centrale

L'atelier Gestion de la faune sur les concessions de l'exploitation forestiere d'Afrique centrale s'est tenu a la reserve de la Lope, au Gabon, du 3 au 10 novembre 2000. Il a ete organise sous t'egide de l'Association pour te developpement de l'information environnementale (ADIE) et sous les auspices de plusieurs bailleurs de fonds (FFEM(1), CI(2), CIFOR(3), USFS(4), WWF- CARPO(5). Des representants de divers secteurs (recherche, industrie du bois, gouvernements, bailleurs de fonds, ONG...) ont partage leurs connaissances et ont cherche a reduire l'impact de l'exploitation forestiere sur les grands mammiferes. Les recommandations vont servir a lancer une serie d'actions, a suivre leur mise en oeuvre, a poursuivre un dialogue intersectoriel et a ajuster les actions. (Resume d'auteur)

Ebola hemorrhagic fever (EHF): mechanism of transmission and pathogenicity.

Hemorrhagic fevers represent a wide spectrum of viral infectious diseases, out-breaking mostly as epidemics, some of them being highly lethal. They range from those caused by bunyaviridae, associated with renal or pulmonary syndromes and those recently emerging and caused by the filoviridae family of thread-like viruses. Among the latter, Ebola hemorrhagic fever (EHF) bears the highest mortality and morbidity rates. One form of the disease has been documented only in monkeys. The human form, has occurred mainly in areas surrounding rain forests in central Africa. Patients present with signs of hemorrhagic diathesis, fever, diarrhea and neurological disorders, leading sometimes to confusion with local endemic diseases. Fatal victims of the disease die of dehydration. Poor hygienic conditions facilitate the spread of the virus. Biologically, the virus seems to target both the host blood coagulative and immune defense systems. Intensive epidemiologic search have failed to establish the definitive natural host of the virus. Twice, with a 19-year interval, major outbreaks have taken place in the Democratic Republic of the Congo. The second major outbreak in the northwestern city of Kikwit in April 1995 will serve here to elucidate the mechanism of the viral infection.

Central African forests, carbon and climate change

The tropical forests of the world are receiving considerable attention in terms of their role in climate change. Not only does tropical land use change provide an important term in balanc- ing the global carbon budget, but tropical forests also present opportunities for carbon trading in the emerging carbon markets. The Congo Basin contains the second largest area of contiguous rainforest in the world, yet for various reasons has received relatively little attention in terms of these climate change issues. This paper provides an assessment of the current state of the forests of Central Africa, their carbon stock, recent rates of deforestation and a simple predictive model of forest change over the next 60 yr. The roles of agriculture and logging which are driving deforestation are discussed. The future of the forests, whether for commercial use, carbon trading or biodiversity is inextricably linked to how these valuable resources are managed. Suggestions are made for potential carbon trading projects, forest management strategies and a climate change research agenda for the region. Effective forest monitoring and management are seen as essential components for the economic development of this region.

A sediment-based history of medium altitude forest in central Africa: a record from Kabata Swamp, Ndale volcanic field, Uganda

1 Sedimentary data from a 6-m long core from Kabata Swamp, an in-filled crater in the Ndale volcanic field of western Uganda, provided evidence for a number of cycles of disturbance and recovery of medium altitude forest. 2 The date of formation of the crater was earlier than an Accelerator Mass Spectrometry (AMS) radiocarbon date of 11 460 ± 90 bp (11 699–11 209bc cal.) and thus appears to predate volcanism farther north in the Fort Portal area. 3 A form of medium altitude forest was already present in western Uganda by the later stages of the last ice age. A more diverse form of medium altitude forest was present from 11 460 ± 90 bp. 4 Some phases of disturbance of this forest during the Holocene could be correlated with established political–economic changes in the study area. One dated c. 2500 bp (768–542 bc cal.) could be associated with the entry of Bantu-speaking people. A second at 400 ± 60 bp (ad 1419–1648 cal.) coincides with significant shifts in the focus of settlement from drier grassland to wetter, more forested parts. 5 Levels of biodiversity in forests in western Uganda remain relatively high, even after substantial modifications of vegetation cover over an extended period of time. Many central African forest taxa may therefore be able to cope with environmental change, including prolonged human impact.

Habitat use and resource tracking by African Ceratogymna hornbills: implications for seed dispersal and forest conservation

AbstractConservation of tropical forests requires an understanding of the seasonal patterns of abundance and distribution of important seed dispersers. In the forests of Central Africa, three species of hornbills in the genus Ceratogymna (Aves: Bucerotidae) provide dispersal for over 50 species of trees and lianas, yet their ecology is poorly known. We present the first empirical evidence for resource tracking and large‐scale movements by two of these species, which were previously considered resident. Hornbill numbers and fruit production were estimated over a one‐year period in the Dja Reserve, Cameroon. Monthly abundances of C. atrata and C. cylindricus varied four‐ and 12‐fold, respectively, and were predicted by community fruit availability as measured by fruitfall on a 4.3 km trail. In contrast, C. fistulator abundances varied little and were not related to fruit availability. Synchronous population fluctuations in sites 22 km distant were observed for atrata and cylindricus, but not for fistulator. Together, these results indicate that atrata and cylindricus populations track fruit resources via seasonal emigrations, while the fistulator population appears to be relatively sedentary. Comparisons of hornbill densities in primary and secondary forests suggest that they are important dispersers in both habitats, and will likely play larger roles in central African forest regeneration as more vulnerable seed dispersers are removed by hunting. If large seasonal movements of hornbills turn out to be a general phenomenon, effective management of central African forest reserves will require greater emphasis on reserve connectivity and on seasonal and spatial patterns of fruit production.