Southeast Cameroon Research Articles

Mandrill (Mandrillus sphinx) Presence in Southeast Cameroon Confirmed By Camera Traps and Indigenous Knowledge

Mandrill (Mandrillus sphinx) Presence in Southeast Cameroon Confirmed By Camera Traps and Indigenous Knowledge

Piezometric Modelling of a Hard Rock Aquifer System in An Intertropical Zone: The Case of the Batouri Mining District (South-East Cameroon)

Piezometric Modelling of a Hard Rock Aquifer System in An Intertropical Zone: The Case of the Batouri Mining District (South-East Cameroon)

Analysis of geochemical data of river sediments and petrographical evaluation of rock basement in the Lomié region, South-East Cameroon: implication on mineralization

Analysis of geochemical data of river sediments and petrographical evaluation of rock basement in the Lomié region, South-East Cameroon: implication on mineralization

The Future Is in the Younger Generations: Baka Children in Southeast Cameroon Have Extensive Knowledge on Medicinal Plants

AbstractIn the context of global change, understanding the knowledge and values given to plants is crucial for choosing relevant approaches towards a more sustainable future. Children are central holders of ethnobotanical knowledge, yet they are still under-considered in ethnobotany. Our study explored the medicinal knowledge of children of the Baka, forager-horticulturalists from Cameroon. We assessed the diversity of medicinal plants they know, the different ailments treated, and whether they could name complete herbal recipes. Using a mixed-methods approach, we combined ex situ interviews (freelisting and knowledge surveys) with in situ methods (walk-in-the-woods trips with voucher collection) with 106 children from 5 to 16 years old. They listed 128 local names of medicinal plants, which we linked to 126 different plant species. While the ex situ and in situ methods had some overlap in the diversity of medicinal plants reported, they also revealed substantial knowledge unique to each method. Our insights provide further evidence of children’s considerable ethnobotanical knowledge and the extent to which different field methods can retrieve such knowledge. We discuss the methodological tools to be developed with and for children to put childhood at the center stage of ethnobotanical approaches for the future.

Natural regeneration in tropical forests along a disturbance gradient in South-East Cameroon

The dynamics of tropical forests are highly dependent on the forest understorey. Understanding its diversity and composition is essential to ensure sustainable management of forest ecosystems. In this study, following a gradient of human disturbance, we analysed the density, diversity and floristic composition of the forest understorey in three land use types of south-eastern Cameroon: a protected area, a selective logging concession and community forests. Vegetation was inventoried in thirty-three permanent one-hectare plots. Woody individuals (tree, shrub, liana) were classified in four strata depending on their diameter: seedling (dbh < 1 cm), sapling (1–9.9 cm), small trees (10–29.9 cm), large tree (≥30 cm). A total of 4,159 individuals (dbh < 10 cm) belonging to 418 species and 232 genera were recorded. They mainly represent tree species (65%) and shade tolerant plants (77%), with diaspores disseminated by animals (74%). Life forms and modes of dissemination were significantly different between land use types. Abundance, species richness and diversity of juveniles varied significantly between strata and land use types: they were globally the highest in plots that have been logged less than five years before inventory. In terms of species composition, the different land use types were not clearly separated, indicating some resilience to disturbance. A low similarity between strata was observed. In all types, most canopy species are light demanding and cannot regenerate in the understorey. This indicates a natural evolution of the forest stands in the absence of silviculture. The presence of species that currently dominate the canopy of these forests will be gradually reduced without human intervention.

Redistribution and fractionation of trace and rare earth elements during weathering and lateritization of orthogneiss in Ndokayo (Bétaré-Oya Gold District, South East Cameroon)

Ferralsols in the transitional zone between the Adamaoua and the South Cameroonian plateaus provided evidence of significant economical and scientific interests, but they have received very little attention over the last decades. Thus, macroscopic, mineral and geochemical investigations of two residual soil profiles from orthogneiss in the Bétaré-Oya Gold District (BOGD) with significant morphological differences were conducted in order to assess weathering and lateritization processes and their significance to the occurrence of mineralized trace and rare earth elements. Macroscopically, soil profile in upslope is deep weathered and thick (> 8.0 m thick), exhibiting a 5.1 m thick encrusted mineral level. Inversely, the downslope soil profile is moderately weathered and marked by a near surface water table that partly affects the mineral horizon B. These studied ferralsols result from an intense weathering but weak to moderate lateritization as revealed by the Chemical Index of Alteration (CIA: 87 to 99%), the Plagioclase Index of Alteration (PIA: 98 to 100%) and the Index of Lateritization (IOL: 31.48 to 60.83%). The two soil profiles have a similar mineralogical content characterized by the predominance of newly-formed secondary minerals such as kaolinite (12–40%), gibbsite (12–27%), goethite (7–15%), hematite (2–15%), maghemite (6–10%) and anatase (1–2%). However, a considerable amount of residual quartz (16–56%) and muscovite (3–15%) is evidenced in the weathering products. Geochemically, the weathering products of Ndokayo show weak to moderate depletion of SiO2 (77.26–31.82%), strong depletion of alkali and alkaline earths (Weathering Index of Parker or WIP: 56.73 to 1.56), and moderate enrichment of Al2O3 (12.43–29.20%), Fe2O3 (1.26–23.45%) and TiO2 (0.11–1.77%). V (64.67–210 ppm) and Cr (25.81–720 ppm) are the most enriched trace elements in this area, with their respective maximum enrichment factor of 2 and 7, and display similar geochemical patterns with Fe2O3, suggesting their adsorption or incorporation into the crystalline structure of Fe-oxides. Some others mineralized trace elements (Sc, Ga, As, Mo, Sn, Cs, Pb, Bi, Th and U) exhibit low to moderate contents, even if their mineralization indices range between 1 and 81. This is indicative of low mining potential of the Ndokayo weathering products. Finally, the deep and intense weathering of orthogneiss, coupled with weak to moderate lateritization of the weathering products in the study area is controlled by rock type involving the formation of kaolinitic laterites and bauxitious kaolins with weak mineralization indices of some trace and rare earth elements.

Petrography and geochemistry of the Moloundou pelite–chert complex and high-grade iron ore, southeast Cameroon: implications for provenance and tectonic setting

Petrography and geochemistry of the Moloundou pelite–chert complex and high-grade iron ore, southeast Cameroon: implications for provenance and tectonic setting

The Mobilong alluvial diamond field of southeast Cameroon: Revised economic potential and sedimentological attributes

Since they were first discovered in the 1930s, the diamond placers that are dispersed intermittently along Cameroon's eastern frontier with the Central African Republic have been the subject of numerous exploration campaigns. These small placers, mainly confined to Quaternary sediments, have never been mined on a large and commercial scale, but have instead been, and continue to be, exploited by the artisanal mining sector. From exploration in the 1980s, the Mobilong alluvial field was recognised to have economic potential based on a manually directed exploration campaign, but gravel sample volumes used for grade estimation are considered to be unrepresentatively small in this study. Recent mechanical mining and bulk trench sampling of this alluvial field, however, yielded greater gravel volumes, which allowed for a modern reassessment of the placer's sedimentology and diamond potential. It demonstrated that this alluvial field is overall a low-volume, small-diamond and uneconomic placer, with higher diamond concentrations in localised areas. The low potential is attributed to the limited availability of diamonds from secondary detrital sources, coupled with the inefficiency of fluvial mechanisms to promote diamond concentration. With unknown kimberlite occurrences in Cameroon and the neighbouring Central African Republic, Proterozoic and Cretaceous successions are considered to be detrital hosts of diamonds; a re-evaluation of these provide insight into their diamond contribution to the Mobilong alluvial field.

Impacts of the COVID-19 pandemic on livelihoods and wild meat use in communities surrounding the Dja Faunal Reserve, South-East Cameroon.

The COVID‐19 outbreak has had considerable negative impacts on the livelihoods and living conditions of communities around the world. Although the source of COVID‐19 is still unknown, a widely spread hypothesis is that the virus could be of animal origin. Wild meat is used by rural communities as a source of income and food, and it has been hypothesised that the pandemic might alter their perceptions and use of wild meat. McNamara et al. (2020) developed a causal model hypothesising how the impacts of the pandemic could lead to a change in local incentives for wild meat hunting in sub‐Saharan African countries. From February 27 to March 19, 2021, we carried out a survey around the Dja Faunal Reserve, Southeast Cameroon, to test McNamara et al.’s model in practice, using semi‐structured questionnaires to investigate the impacts of the COVID‐19 outbreak on wild meat hunting and consumption. Our results generally agree with the causal pathways suggested by McNamara et al. However, our study highlights additional impact pathways not identified in the model. We provide revisions to McNamara's model to incorporate these pathways and inform strategies to mitigate the impacts of the pandemic.

Rapid dung removal by beetles suggests higher duiker densities in Central African rainforests

AbstractFor many mammal species, converting dung density into population density requires accurate estimates of defaecation rate and dung survival time. The latter parameter probably varies seasonally. In Nki National Park, south-east Cameroon, we monitored 216 dung piles of the blue duiker Philantomba monticola and 373 of the red duiker group (Cephalophus spp.), major game animals in Central Africa, and estimated dung survival time across seasons. Mean survival time was 6.83 days in the major dry season and 1.21–1.81 in other seasons for the blue duiker, and 7.37 and 1.53–4.05 for red duikers, lower than the values conventionally used for density estimations in Central Africa (i.e. 18 days for the blue duiker and 21 days for red duikers). Overall, beetles removed half of the dung within 1 day of deposition. However, the proportion of dung piles that beetles removed was significantly lower in the major dry season, and other dung piles remained longer until they disappeared as a result of other factors. As shorter dung survival time results in higher estimates of population density, our findings imply that in forests with intense beetle activity, duiker densities are higher than those based on the conventional values of dung survival time. Duiker densities and dung survival time should be estimated simultaneously. To minimize the bias introduced by rapid removal of fresh dung by beetles, only fresh dung (&lt; 3 hours old) should be monitored when estimating mean dung survival time.

The impacts of human activity on mammals in a community forest near the Dja Biosphere Reserve in Cameroon

AbstractHuman activity in African tropical rainforests continues to threaten wild mammals. Many rural communities are dependent on hunting, yet there is a widespread lack of baseline data on ecology and the sustainability of hunting. We investigated the impacts of human activity on mammal species composition and distributions within a community forest surrounding a village in the buffer zone of the Dja Biosphere Reserve in south-east Cameroon. We conducted a camera-trap survey in August–November 2017 and detected 24 mammal species, including Critically Endangered western lowland gorilla Gorilla gorilla gorilla, Endangered central African chimpanzee Pan troglodytes troglodytes and Endangered tree pangolin Phataginus tricuspis. We used occupancy analysis to explore relationships between indicators of human activity (distance to a road and the Reserve), habitat quality (distance to the river and tree cover) and the distributions of species. We found that the local distribution of threatened mammals was not apparently limited by human activity, and proximity to the road did not negatively influence occupancy for any species. However, most of the Reserve's large species were not detected, including the African forest elephant Loxodonta cyclotis and the largest ungulates, and the occupancy of two species commonly hunted for wild meat was positively correlated with distance from the village, indicating hunting may be unsustainable. Our results show that the community forest provides habitat for threatened species outside the Reserve and in close proximity to people. However, effective conservation management will require continued monitoring and research to determine whether current rates of hunting are sustainable.

Weak to Moderate Lateritization Inducing Trace and Re Elements Mineralization in Weathering Products Derived from Orthogneiss in Ndokayo (Bétaré-Oya Gold District, South-East Cameroon)

Weak to Moderate Lateritization Inducing Trace and Re Elements Mineralization in Weathering Products Derived from Orthogneiss in Ndokayo (Bétaré-Oya Gold District, South-East Cameroon)

Methods to measure biological sounds and assess their drivers in a tropical forest

The study of soundscapes and biological sounds is becoming the focus of increasing scientific attention. Studying biological sounds involves the deployment of acoustic sensors to record sounds and the identification of animal species and other sources of sound in audio recordings. In addition, data extracted from audio recordings may be pooled together with ecological and human activity data to investigate the drivers of biological sounds. We provide a detailed method description of our study on biological sounds in a tropical forest and their drivers along a gradient of disturbance in Southeast Cameroon. We designed and implemented a research protocol to:•make large scale audio recordings and identify animal species detected;•collect ground-truth data on mammal and bird species;•collect climate, habitat, and human activity data and describe remoteness and accessibility.

Assessing the structure and drivers of biological sounds along a disturbance gradient

Studying soundscapes to improve knowledge about an environment with limited visibility is gaining popularity. However, the structure and drivers of biological sounds remain poorly understood although this information can improve understanding of landscape dynamics. To describe biological sounds and provide a better understanding of their drivers, we conducted a study aiming at detecting and identifying individual vocalising animal species, determining the abundance, diversity, and composition of vocalisations, and assessing how ecological and anthropogenic factors affect these sounds. Sounds were recorded from February through May 2020 in southeast Cameroon, using passive acoustic monitoring, in three study sites representing a gradient of disturbance. Local experts listened to 20,485 1-min files of recorded sounds to identify vocalising species. These identifications, in combination with anthropogenic and ecological data from the field, were used to assess abundance, diversity, and composition of vocalisations. Fifteen vocalising mammal species and 37 vocalising bird species were identified. Overall, insects and, to a lesser extent, birds were the most dominant animal classes in the soundscape. Furthermore, vocalisation abundance and the diversity of vocalising mammals did not vary along the disturbance gradient, whereas vocalisation abundance of birds was lowest in the site where anthropogenic disturbance was least present. Moreover, both mammal and bird vocal activity were negatively impacted by rainfall. Human activity and the amount of swamp habitat reduced the vocal activity of mammals, but these factors did not affect bird vocalisations. For birds, the diversity of vocalisations was positively affected by bird abundance and negatively affected by higher temperatures. Our results indicate that animal classes do not have the same number of acoustically active species and produce differing amounts of sound, thus highlighting that sources of sound do not make equal contributions to the soundscape and furthering knowledge of soundscape structure. They also show that the effects of anthropogenic and ecological factors on biological sounds vary depending on the sound source, which suggests that soundscape components are differently affected by soundscape drivers. Additionally, our study provides baseline acoustic information on vocalising species in African tropical rainforests. This acoustic information may be used for automated detections of vocalisations in the future. Together, an understanding of soundscape drivers and information on vocalising species can contribute to the development of applications that will monitor soundscapes and detect important changes in landscapes. This will help guide future decision making and landscape conservation planning.

The importance of choosing appropriate methods for assessing wild food plant knowledge and use: A case study among the Baka in Cameroon.

In tropical rainforests, access to and availability of natural resources are vital for the dietary diversity and food security of forest-dwelling societies. In the Congo Basin, these are challenged by the increasing exploitation of forests for bushmeat, commercial hardwood, mining, and large-scale agriculture. In this context, a balanced approach is needed between the pressures from forest exploitation, non-timber forest product trade and the livelihood and dietary behavior of rural communities. While there is a general positive association between tree cover and dietary diversity, the complex biocultural interactions between tropical forest food resources and the communities they sustain are still understudied. This research focuses on the knowledge and use of wild food plants by the forest-dwelling Baka people in southeast Cameroon. By using two different sets of methods, namely ex-situ interviews and in-situ surveys, we collected ethnographic and ethnobotanical data in two Baka settlements and explored the diversity of wild edible plants known, the frequency of their consumption, and potential conflicts between local diet and commercial trade in forest resources. Within a single Baka population, we showed that the in-situ walk-in-the-woods method resulted in more detailed information on wild food plant knowledge and use frequency than the ex-situ methods of freelisting and dietary recalls. Our in-situ method yielded 91 wild edible species, much more than the ex-situ freelisting interviews (38 spp.) and dietary recalls (12 spp.). Our results suggest that studies that are based only on ex-situ interviews may underestimate the importance of wild food plants for local communities. We discuss the limitations and strengths of these different methods for investigating the diversity of wild food plant knowledge and uses. Our analysis shows that future studies on wild food plants would profit from a mixed approach that combines in-situ and ex-situ methods.

Mechanical Behavior of Pericopsis elata Relative to Age during Growth

The assamela (afrormosia) whose scientific name is “Pericopsis elata” (Harms), a large tree of great commercial value, is an exploited species. It is considered “endangered” by the IUCN.” Trees ready for harvesting are scarce because the logging diameter, which has been set at 100 cm, is very big. The studies recommended by the Cameroonian government as part of the ITTO/CITES project activities should be carried out to determine a new minimum logging diameter as the diameter increases with age. No credible solution is provided in the scientific literature to compensate for its scarcity of exploitation. Moreover, little or no information is available for describing the variation of its mechanical properties over time in order to determine the age at which its wood mechanical properties are good enough to be marketable. It is in this context that this work was undertaken. In this study, we adopted an experimental approach to evaluate the mechanical properties of this species exploited in southeast Cameroon. We then studied the variations in these properties as a function of tree age in order to propose leads for their exploitation. Thus, the compression and bending tests allowed us to estimate the relationship between the mechanical properties in three main directions of the log (MOE in compression and bending, failure stress in compression and bending, and creep in compression) and age (or diameter). We also used the 10‐hour creep under low axial compressive loading data to implement the theoretical fractional Maxwell (MF) model, which was compared to the experimental data. For this purpose, after three months of natural drying in the laboratory, we evaluated the above mechanical properties according to age. This study shows that the mechanical properties change as the diameter increases and change very quickly from 70 cm diameter upwards. From the analysis of the experimental data, we deduced that the minimum diameter of exploitable trees should be equal to 80 cm corresponding to the age of about 200 years.

Mapping suitable great ape habitat in and around the Lobéké National Park, South-East Cameroon.

As a result of extensive data collection efforts over the last 20–30 years, there is quite a good understanding of the large‐scale geographic distribution and range limits of African great apes. However, as human activities increasingly fragment great ape spatial distribution, a better understanding of what constitutes suitable great ape habitat is needed to inform conservation and resource extraction management. Chimpanzees (Pan troglodytes troglodytes) and gorillas (Gorilla gorilla gorilla) inhabit the Lobéké National Park and its surrounding forest management units (FMUs) in South‐East Cameroon. Both park and neighboring forestry concessions require reliable evidence on key factors driving great ape distribution for their management plans, yet this information is largely missing and incomplete. This study aimed at mapping great ape habitat suitability in the area and at identifying the most influential predictors among three predictor categories, including landscape predictors (dense forest, swampy forest, distance to water bodies, and topography), human disturbance predictors (hunting, deforestation, distance to roads, and population density), and bioclimatic predictor (annual precipitation). We found that about 63% of highly to moderately suitable chimpanzee habitat occurred within the Lobéké National Park, while only 8.4% of similar habitat conditions occurred within FMUs. For gorillas, highly and moderately suitable habitats occurred within the Lobéké National Park and its surrounding FMUs (82.6% and 65.5%, respectively). Key determinants of suitable chimpanzee habitat were hunting pressure and dense forest, with species occurrence probability optimal at relatively lower hunting rates and at relatively high‐dense forest areas. Key determinants of suitable gorilla habitat were hunting pressure, dense forests, swampy forests, and slope, with species occurrence probability optimal at relatively high‐dense and swampy forest areas and at areas with mild slopes. Our findings show differential response of the two ape species to forestry activities in the study area, thus aligning with previous studies.

Provenance and weathering conditions of the Moloundou swamp sediments, southeast Cameroon: Evidence from mineralogy and geochemistry

This work reports the mineralogical and geochemical characterization of the Moloundou swamp sediments in order to deduce their tectonic setting, source rock composition, weathering conditions and maturity. These sediments show sandy to loamy sand in nature; they are pale olive to greenish and contain organic matter in the top. Their mineralogy consists of quartz and clay minerals with small amounts of mica, rutile, anatase and feldspars. Tectonic discrimination diagrams and plots of K2O/Na2O vs. SiO2, and TiO2 versus Zr, intermediate sedimentary provenance, within active continental margins in a collisional setting. The A–CN–K ternary diagram points to a high degree of chemical weathering of the source area. The increased plagioclase index of alteration (PIA) values point to a high leaching of plagioclase feldspars during source weathering and transport. The chemical index of alteration (CIA) and the chemical index of weathering (CIW) values for the studied samples suggest a highly intensive chemical weathering in a humid warm climate. The strong chemical weathering of the source rocks is revealed by the presence of kaolinite, goethite and gibbsite. The Moloundou swamp sediments are tectonically in an active setting, derived from mixed acid to intermediate magmatic and metamorphic source rocks.

From Bush Mangoes to Bouillon Cubes: Wild Plants and Diet among the Baka, Forager-Horticulturalists from Southeast Cameroon

Increasing deforestation affects tropical forests, threatening the livelihoods of local populations who subsist on forest resources. The disappearance of wild plants and animals and the increasing influence of market economies affect local health, well-being, and diet. The impact of these changes on wild meat consumption has been well documented, but little attention has been given to wild edible plants, despite their importance as sources of calories and micronutrients. Furthermore, the relationships among food behavior strategies adopted by local populations, their psycho-cultural representations of food, and their food preferences have been poorly explored. In this study, we investigate food behaviors with an emphasis on the role of wild edible plants among a forager-horticulturalist society from the Congo Basin: the Baka. By combining an ethnobotanical survey with data from interviews (n = 536) related to food behaviors and representations of food, our data show that the Baka valorize both agricultural and marketable foods, and that wild plants represent a minor part of their diet, both in frequency and diversity. Finally, by examining how some wild edible plants have shifted from being eaten to being sold, we explore how market-oriented uses of wild edible plants may affect dietary behaviors and biocultural resilience.

Dynamics of Land Use and the Evolution of Agroforestry Practices in the Dja Biosphere Reserve (DBR) Southeast Cameroon

The study had as objective to investigate the land use/land cover change from 1980 to 2019 in the Dja Biosphere Reserve using GIS and remote sensing techniques and the evolution of agroforestry practices. Semi structured questionnaires were administered to 320 farmers who were randomly selected from 35 villages of the Dja Biosphere Reserve characterized by the presence of agroforestry systems. The land use map revealed six classes which were dense humid forest, perennial crop-based agroforestry practices, river, wetland, built up and bare areas. Between 1980 and 2008, dense humid forest lost -4.9% of its area to the benefits of perennial crop-based agroforestry practices, built up and bare land. Between 2008 and 2019, dense humid forest gain 1.77% of its area due to increase in perennial crop-based agroforestry practices and a subsequent increase in vegetation cover. Perennial crop-based agroforestry practices and built up increase progressively from 1980 to 2019. Farmers perceived hunting (36.3%), slash and burn agriculture (43.3%) and harvesting of tree-based products (20.3%) as the anthropogenic activities impacting the reserve negatively. The evolution of agroforestry practices were observed on the field, but the precise area under agroforestry practices in the study area need to be estimated. As a mitigation strategy to livelihood needs as well as the rehabilitation of degraded land, the conversion of pure cultivated agricultural land into agroforestry is a major opportunity.