Early anthropogenic impact on Western Central African rainforests 2,600 y ago


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laura.epp [ at ] awi.de

Abstract

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.



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ISI/Scopus peer-reviewed
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Published
Eprint ID
47061
DOI 10.1073/pnas.1715336115

Cite as
Garcin, Y. , Deschamps, P. , Ménot, G. , de Saulieu, G. , Schefuß, E. , Sebag, D. , Dupont, L. M. , Oslisly, R. , Brademann, B. , Mbusnum, K. G. , Onana, J. M. , Ako, A. A. , Epp, L. S. , Tjallingii, R. , Strecker, M. R. , Brauer, A. and Sachse, D. (2018): Early anthropogenic impact on Western Central African rainforests 2,600 y ago , Proceedings of the National Academy of Sciences, 115 (13), pp. 3261-3266 . doi: 10.1073/pnas.1715336115


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