Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Proceedings of the National Academy of Sciences of the United States 3261-3266 PALEOENVIRONNEMENT PALEOCLIMAT HOLOCENE FORET MOSAIQUE FORET SAVANE FACTEUR ANTHROPIQUE HYDROLOGIE LAC HISTOIRE DU PEUPLEMENT CAMEROUN SUD OUEST ZONE TROPICALE BAROMBI LAC 2018 fdi:010072522 ENG Proceedings of the National Academy of Sciences of the United States 0027-8424 ISI:000428382400038 13 10.1073/pnas.1715336115 https://www.documentation.ird.fr/hor/fdi:010072522 https://www.documentation.ird.fr/intranet/publi/depot/2018-04-16/010072522.pdf 115 Horizon (IRD) A potential human footprint on Western Central African rainforests before the Common Era has become the focus of an ongoing controversy. Between 3,000 y ago and 2,000 y ago, regional pollen sequences indicate a replacement of mature rainforests by a forest–savannah mosaic including pioneer trees. Although some studies suggested an anthropogenic influence on this forest fragmentation, current interpretations based on pollen data attribute the "rainforest crisis" to climate change toward a drier, more seasonal climate. A rigorous test of this hypothesis, however, requires climate proxies independent of vegetation changes. Here we resolve this controversy through a continuous 10,500-y record of both vegetation and hydrological changes from Lake Barombi in Southwest Cameroon based on changes in carbon and hydrogen isotope compositions of plant waxes. δ13C-inferred vegetation changes confirm a prominent and abrupt appearance of C4 plants in the Lake Barombi catchment, at 2,600 calendar years before AD 1950 (cal y BP), followed by an equally sudden return to rainforest vegetation at 2,020 cal y BP. δD values from the same plant wax compounds, however, show no simultaneous hydrological change. Based on the combination of these data with a comprehensive regional archaeological database we provide evidence that humans triggered the rainforest fragmentation 2,600 y ago. Our findings suggest that technological developments, including agricultural practices and iron metallurgy, possibly related to the large-scale Bantu expansion, significantly impacted the ecosystems before the Common Era. 112ARCHEO02 ; 021ENVECO ; 021CLIMAT01 UR161 / UR208 / UR050 Cameroun / Gabon