Institute Of Recherche En Ecologie Tropicale

Libreville, Gabon

Institute Of Recherche En Ecologie Tropicale

Libreville, Gabon
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Coad L.,University of Oxford | Schleicher J.,University of Oxford | Schleicher J.,University of Cambridge | Milner-Gulland E.J.,Imperial College London | And 8 more authors.
Conservation Biology | Year: 2013

Despite widespread recognition of the major threat to tropical forest biological diversity and local food security posed by unsustainable bushmeat hunting, virtually no long-term studies tracking the socioecological dynamics of hunting systems have been conducted. We interviewed local hunters and collected detailed hunting data to investigate changes in offtake and hunter characteristics over 10 years (2001-2010) in Dibouka and Kouagna villages, central Gabon, in the context of hunter recollections of longer term trends since the 1950s. To control for changes in hunter behavior, such as trap location and characteristics, we report hunting offtake data per trap. Our results suggest the hunting area was already highly depleted by 2001; local hunters reported that 16 large-bodied prey species had become rare or locally extirpated over the last 60 years. Overall, we observed no significant declines in hunting offtake or changes in species composition from 2001 to 2010, and offtakes per trap increased slightly between 2004 and 2010. However, trapping distance from the villages increased, and there was a switch in hunting techniques; a larger proportion of the catch was hunted with guns in 2010. The number of hunters declined by 20% from 2004 to 2010, and male livelihood activities shifted away from hunting. Hunters with the lowest hunting incomes in 2004 were more likely than successful hunters to have moved away from the village by 2010 (often in response to alternative employment opportunities). Therefore, changes in trap success (potentially related to biological factors) were interacting with system-level changes in hunter number and composition (related to external socioeconomic factors) to produce a relatively static overall offtake. Our results highlight the importance of understanding the small-scale context of hunting to correctly interpret changes or apparent stasis in hunting effort and offtake over time. © 2013 Society for Conservation Biology.

Oslisly R.,IRD Montpellier | White L.,British Petroleum | White L.,Institute Of Recherche En Ecologie Tropicale | White L.,University of Stirling | And 5 more authors.
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2013

Central Africa includes the world's second largest rainforest block. The ecology of the region remains poorly understood, as does its vegetation and archaeological history. However, over the past 20 years, multidisciplinary scientific programmes have enhanced knowledge of old human presence and palaeoenvironments in the forestry block of Central Africa. This first regional synthesis documents significant cultural changes over the past five millennia and describes how they are linked to climate. It is now well documented that climatic conditions in the African tropics underwent significant changes throughout this period and here we demonstrate that corresponding shifts in human demography have had a strong influence on the forests. The most influential event was the decline of the strong African monsoon in the Late Holocene, resulting in serious disturbance of the forest block around 3500 BP. During the same period, populations from the north settled in the forest zone; they mastered new technologies such as pottery and fabrication of polished stone tools, and seem to have practised agriculture. The opening up of forests from 2500 BP favoured the arrival of metallurgist populations that impacted the forest. During this long period (2500-1400 BP), a remarkable increase of archaeological sites is an indication of a demographic explosion of metallurgist populations. Paradoxically, we have found evidence of pearl millet (Pennisetum glaucum) cultivation in the forest around 2200 BP, implying a more arid context. While Early Iron Age sites (prior to 1400 BP) and recent pre-colonial sites (two to eight centuries BP) are abundant, the period between 1600 and 1000 BP is characterized by a sharp decrease in human settlements, with a population crash between 1300 and 1000 BP over a large part of Central Africa. It is only in the eleventh century that new populations of metallurgists settled into the forest block. In this paper, we analyse the spatial and temporal distribution of 328 archaeological sites that have been reliably radiocarbon dated. The results allow us to piece together changes in the relationships between human populations and the environments in which they lived. On this basis, we discuss interactions between humans, climate and vegetation during the past five millennia and the implications of the absence of people from the landscape over three centuries. We go on to discuss modern vegetation patterns and African forest conservation in the light of these events. © 2013 The Authors.

Mitchard E.T.A.,University of Edinburgh | Saatchi S.S.,Jet Propulsion Laboratory | White L.J.T.,Agence Nationale des Parcs Nationaux | White L.J.T.,University of Stirling | And 13 more authors.
Biogeosciences | Year: 2012

Spatially-explicit maps of aboveground biomass are essential for calculating the losses and gains in forest carbon at a regional to national level. The production of such maps across wide areas will become increasingly necessary as international efforts to protect primary forests, such as the REDD+ (Reducing Emissions from Deforestation and forest Degradation) mechanism, come into effect, alongside their use for management and research more generally. However, mapping biomass over high-biomass tropical forest is challenging as (1) direct regressions with optical and radar data saturate, (2) much of the tropics is persistently cloud-covered, reducing the availability of optical data, (3) many regions include steep topography, making the use of radar data complex, (5) while LiDAR data does not suffer from saturation, expensive aircraft-derived data are necessary for complete coverage. We present a solution to the problems, using a combination of terrain-corrected L-band radar data (ALOS PALSAR), spaceborne LiDAR data (ICESat GLAS) and ground-based data. We map Gabon's Lopé National Park (5000 km2) because it includes a range of vegetation types from savanna to closed-canopy tropical forest, is topographically complex, has no recent contiguous cloud-free high-resolution optical data, and the dense forest is above the saturation point for radar. Our 100 m resolution biomass map is derived from fusing spaceborne LiDAR (7142 ICESat GLAS footprints), 96 ground-based plots (average size 0.8 ha) and an unsupervised classification of terrain-corrected ALOS PALSAR radar data, from which we derive the aboveground biomass stocks of the park to be 78 Tg C (173 Mg C ha-1). This value is consistent with our field data average of 181 Mg C ha-1, from the field plots measured in 2009 covering a total of 78 ha, and which are independent as they were not used for the GLAS-biomass estimation. We estimate an uncertainty of ± 25% on our carbon stock value for the park. This error term includes uncertainties resulting from the use of a generic tropical allometric equation, the use of GLAS data to estimate Lorey's height, and the necessity of separating the landscape into distinct classes. As there is currently no spaceborne LiDAR satellite in operation (GLAS data is available for 2003-2009 only), this methodology is not suitable for change-detection. This research underlines the need for new satellite LiDAR data to provide the potential for biomass-change estimates, although this need will not be met before 2015. © 2012 Author(s).

Van der Hoek Y.,City University of New York | Van der Hoek Y.,CUNY - College of Staten Island | Lustenhouwer I.,Wageningen University | Jeffery K.J.,British Petroleum | And 3 more authors.
African Journal of Ecology | Year: 2013

Seasonality and management are factors that may affect the diet selection of the forest buffalo (Syncerus caffer nanus). Fire is considered a major driving force in savannah systems and prescribed burning is a commonly applied conservation tool in protected areas such as Lopé National Park, Gabon. Prescribed annual fires contribute to the maintenance of open areas and provide high-quality forage for forest buffalo, a major herbivore in the park. We used microhistological faecal analysis to determine the diet selection of forest buffalo and measured the extent of variation between a dry season, preburn and a wet season, postburn sampling period. The buffalo diet comprised mainly of monocotyledons, primarily grasses (Poaceae) and sedges (Cyperaceae). Intake of open-area-associated plant species was higher in the wet season, postburn treatment sampling period (97%) than the dry season, preburn sampling period (87%), which corresponded conversely to a reduction in forest-associated Marantaceae plants (10% versus 1%). High proportions of grasses and sedges in the diet signify the importance of open areas for forest buffalo. Controlled burning as tool for maintenance of open areas may play a key role in the meta-population management of the forest buffalo. © 2012 Blackwell Publishing Ltd.

Schuttler S.G.,University of Missouri | Philbrick J.A.,University of Missouri | Jeffery K.J.,Agence Nationale des Parcs Nationaux | Jeffery K.J.,University of Stirling | And 2 more authors.
PLoS ONE | Year: 2014

Spatial patterns of relatedness within animal populations are important in the evolution of mating and social systems, and have the potential to reveal information on species that are difficult to observe in the wild. This study examines the fine-scale genetic structure and connectivity of groups within African forest elephants, Loxodonta cyclotis, which are often difficult to observe due to forest habitat. We tested the hypothesis that genetic similarity will decline with increasing geographic distance, as we expect kin to be in closer proximity, using spatial autocorrelation analyses and Tau Kr tests. Associations between individuals were investigated through a non-invasive genetic capture-recapture approach using network models, and were predicted to be more extensive than the small groups found in observational studies, similar to fission-fusion sociality found in African savanna (Loxodonta africana) and Asian (Elephas maximus) species. Dung samples were collected in Lopé National Park, Gabon in 2008 and 2010 and genotyped at 10 microsatellite loci, genetically sexed, and sequenced at the mitochondrial DNA control region. We conducted analyses on samples collected at three different temporal scales: a day, within six-day sampling sessions, and within each year. Spatial autocorrelation and Tau Kr tests revealed genetic structure, but results were weak and inconsistent between sampling sessions. Positive spatial autocorrelation was found in distance classes of 0-5 km, and was strongest for the single day session. Despite weak genetic structure, individuals within groups were significantly more related to each other than to individuals between groups. Social networks revealed some components to have large, extensive groups of up to 22 individuals, and most groups were composed of individuals of the same matriline. Although fine-scale population genetic structure was weak, forest elephants are typically found in groups consisting of kin and based on matrilines, with some individuals having more associates than observed from group sizes alone. © 2014 Schuttler et al.

PubMed | James Cook University, Institute of Tropical Forest Conservation, University of Zürich, Pontifical Catholic University of Ecuador and 59 more.
Type: Journal Article | Journal: Science (New York, N.Y.) | Year: 2016

The biodiversity-productivity relationship (BPR) is foundational to our understanding of the global extinction crisis and its impacts on ecosystem functioning. Understanding BPR is critical for the accurate valuation and effective conservation of biodiversity. Using ground-sourced data from 777,126 permanent plots, spanning 44 countries and most terrestrial biomes, we reveal a globally consistent positive concave-down BPR, showing that continued biodiversity loss would result in an accelerating decline in forest productivity worldwide. The value of biodiversity in maintaining commercial forest productivity alone-US$166 billion to 490 billion per year according to our estimation-is more than twice what it would cost to implement effective global conservation. This highlights the need for a worldwide reassessment of biodiversity values, forest management strategies, and conservation priorities.

Inoue E.,Kyoto University | Akomo-Okoue E.F.,Kyoto University | Akomo-Okoue E.F.,Institute Of Recherche En Ecologie Tropicale | Ando C.,Kyoto University | And 7 more authors.
American Journal of Physical Anthropology | Year: 2013

The male dispersal patterns of western lowland gorillas (WLGs, Gorilla gorilla gorilla) are not well understood. To determine whether most silverbacks stay close to their relatives, we analyzed autosomal and Y-chromosomal microsatellites (STRs) in wild WLGs at Moukalaba, Gabon. We obtained STR genotypes for 38 individuals, including eight silverbacks and 12 adult females in an approximately 40 km2 area. Among them, 20 individuals were members of one identified group (Group Gentil; GG), including one silverback and six adult females. The silverback sired all 13 of the offspring in GG and no Y-STR polymorphism within GG was found, as expected in a one-male group structure. Over all silverbacks sampled, Y-STR diversity was high considering the limited sampling area, and silverbacks with similar Y-STR haplotypes were not always located in nearby areas. Although the misclassification rate of kinship estimates in this study was not negligible, there were no kin dyads among all silverbacks sampled. These results suggest that silverbacks born in the same group do not stay close to each other after maturation. The Y-STR diversity in this study was similar to that of a previous study conducted in an area that was approximately 150 times larger than our study area. Similarity of WLG Y-STR diversity between studies at different sampling scales suggests that male gene flow may not be geographically limited. These results suggest that WLG males normally disperse from their natal areas after maturation, at least, in Moukalaba. © 2013 Wiley Periodicals, Inc.

Paupy C.,IRD Montpellier | Paupy C.,Center International Of Recherches Medicales Of Franceville Cirmf | Makanga B.,Center International Of Recherches Medicales Of Franceville Cirmf | Makanga B.,Institute Of Recherche En Ecologie Tropicale | And 10 more authors.
PLoS ONE | Year: 2013

During the last four years, knowledge about the diversity of Plasmodium species in African great apes has considerably increased. Several new species were described in chimpanzees and gorillas, and some species that were previously considered as strictly of human interest were found to be infecting African apes. The description in gorillas of P. praefalciparum, the closest relative of P. falciparum which is the main malignant agent of human malaria, definitively changed the way we understand the evolution and origin of P. falciparum. This parasite is now considered to have appeared recently, following a cross-species transfer from gorillas to humans. However, the Plasmodium vector mosquito species that have served as bridge between these two host species remain unknown. In order to identify the vectors that ensure ape Plasmodium transmission and evaluate the risk of transfer of these parasites to humans, we carried out a field study in Gabon to capture Anopheles in areas where wild and semi-wild ape populations live. We collected 1070 Anopheles females belonging to 15 species, among which An. carnevalei, An. moucheti and An. marshallii were the most common species. Using mtDNA-based PCR tools, we discovered that An. moucheti, a major human malaria vector in Central Africa, could also ensure the natural transmission of P. praefalciparum among great apes. We also showed that, together with An. vinckei, An. moucheti was infected with P. vivax-like parasites. An. moucheti constitutes, therefore, a major candidate for the transfer of Plasmodium parasites from apes to humans. © 2013 Paupy et al.

Neumann K.,Goethe University Frankfurt | Bostoen K.,Ghent University | Hohn A.,Goethe University Frankfurt | Kahlheber S.,Goethe University Frankfurt | And 3 more authors.
Quaternary International | Year: 2012

Agriculture was introduced into the Central African rainforest from the drier West African savanna, in concert with a major climatic change that amplified seasonality just after 2500 BP. The savanna crop pearl millet (Pennisetum glaucum), dated to 2400-2200 BP, could only be cultivated due to the development of a distinct dry season. Increasing seasonality and the replacement of mature forests by pioneer formations is indicated by Trema orientalis in the pollen diagram of Nyabessan after 2400 BP. However, charcoal data do not point to the existence of savannas in South Cameroon during this period, but rather to a mosaic of mature and pioneer forests. The early rainforest farmers combined the cultivation of pearl millet with the exploitation of wild oil-containing tree fruits, such as oil palm and Canarium. The existence of pioneer formations that can be easily cut favoured the establishment of shifting cultivation. The archaeobotanical finds fit into a linguistic scenario of West-Bantu speakers making the cultivation of pearl millet one of their food production strategies before expanding further to the South. The reconstructed inherited pearl millet vocabulary for the early phases of Bantu language history provides strong circumstantial evidence for an overlap of the major stages of the Bantu expansion with the dispersal of food production. © 2011 Elsevier Ltd and INQUA.

Aleman J.,Center for Bio Archeology and Ecology | Leys B.,Center for Bio Archeology and Ecology | Apema R.,University of Bangui | Bentaleb I.,Montpellier University | And 9 more authors.
Journal of Vegetation Science | Year: 2012

Aim: To calibrate a model of the relationship between bio-proxies (pollen, phytoliths and δ 13C of soil organic matter) and woody cover, measured as the leaf area index (LAI). This relationship, applied in palaeosequences, enables reconstruction of past savanna tree cover. Location: The samples are from tropical Africa. Modern soil samples are from the Central African Republic and past samples are from sediments of lakes in Senegal and Congo. Methods: We analysed the pollen and phytolith content and stable carbon isotope values of 17 soil samples taken from three short transects in the Central African Republic; LAI was measured on the same transects. The indices used were the AP/NAP ratio of arboreal (AP) to non-arboreal (NAP) pollen, the D/P ratio of ligneous dicotyledons (D) to Poaceae (P) phytoliths, and the δ 13C of soil organic matter, i.e. the 13C/ 12C ratio. Results: A multi-proxy model was calibrated. The best model included only a combination of pollen and phytolith as proxies, excluding organic matter δ 13C because of its long mean residence time in the soil. The model was then applied to two palaeosequences in Africa, and a time series of relative LAI changes was obtained, providing new information about vegetation changes. Conclusion: This model can be applied in palaeosequences to reconstruct relative time series of LAI in African savannas and can help interpret vegetation changes quantitatively. This approach is complementary to the description of pollen and phytolith assemblages. © 2011 International Association for Vegetation Science.

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