Early anthropogenic impact on Western Central African rainforests 2,600 y ago
Early anthropogenic impact on Western Central African rainforests 2,600 y ago
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DOI：
10.1073/pnas.1715336115
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发表时间：
2018-03-27
影响因子：
11.1
通讯作者：
Sachse, Dirk
中科院分区：
文献类型：
--
作者：
Garcin, Yannick;Deschamps, Pierre;Sachse, Dirk
在共同时代之前，中非西部热带雨林上潜在的人类足迹已成为一场持续不断的争议的焦点。在3,000年前和2,000年前之间，区域花粉序列表明，成熟的雨林被包括拓荒树在内的森林-稀树草原镶嵌所取代。尽管一些研究表明这种森林碎片化受人为因素的影响，但目前基于花粉数据的解释将“热带雨林危机”归因于气候变化，转向更干燥、更季节性的气候。然而，对这一假设的严格检验需要独立于植被变化的气候指标。在这里，我们通过连续10,500年来记录喀麦隆西南部巴伦比湖的植被和水文变化来解决这一争议，该记录基于植物蜡碳和氢同位素组成的变化。三角洲C-13--推断的植被变化证实了巴龙比湖流域中C-4植物的显著和突然出现，在公元1950年前的2,600个历年(CALY BP)，随后在2,020 CALY BP同样突然恢复热带雨林植被。然而，来自相同植物蜡质化合物的D值并没有显示出同步的水文变化。基于这些数据与一个全面的区域考古数据库的结合，我们提供了2600年前人类引发热带雨林碎片化的证据。我们的发现表明，技术发展，包括农业实践和钢铁冶炼，可能与班图的大规模扩张有关，在共同时代之前对生态系统产生了重大影响。
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. delta C-13-inferred vegetation changes confirm a prominent and abrupt appearance of C-4 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. delta D 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.