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

authors

  • Garcin Yannick
  • Deschamps Pierre
  • Menot Guillemette
  • De Saulieu Geoffroy
  • Schefuß Enno
  • Sebag David
  • Dupont Lydie
  • Oslisly Richard
  • Brademann Brian
  • Mbusnum Kevin
  • Onana Jean-Michel
  • Ako Andrew
  • Epp Laura
  • Tjallingii Rik
  • Strecker Manfred
  • Brauer Achim
  • Sachse Dirk

keywords

  • Western Central Africa
  • Late Holocene
  • Rainforest crisis
  • Paleohydrology
  • Human activity

document type

ART

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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