image: This is a coring platform on Lake Barombi, Cameroon. view more
Credit: <i>PNAS</i>
Researchers report evidence of early human impacts on African rainforests. Regional pollen sequences indicate that a switch from mature rainforest to forest-savannah mosaic occurred in Western Central Africa (WCA) between 3,000 and 2,000 years ago. Consensus attributes the switch, known as the late Holocene rainforest crisis (LHRC), to a drying climate, but an anthropogenic origin has also been proposed. Yannick Garcin and colleagues obtained a sediment core spanning the past 10,500 years from Lake Barombi in southwest Cameroon. Analysis of carbon isotope composition of plant waxes from the sediment indicated a rapid increase in the proportion of grasses relative to trees and shrubs occurring 2,600 years ago, followed by an equally abrupt switch to primarily trees approximately 600 years later, consistent with the LHRC. Contrary to the current consensus, the hydrogen isotope composition of the plant waxes, a marker of hydrological changes, yielded no indication of a coincident shift in climate. Analysis of a database of 460 archaeological sites throughout WCA suggested that the LHRC was associated with rapid human population growth in the region, along with the emergence of pearl millet cultivation, oil palm use, and iron metallurgy. According to the authors, human activities may have driven land-use changes around Lake Barombi and the LHRC may reflect large-scale anthropogenic changes in WCA thousands of years ago.
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Article #17-15336: "Early anthropogenic impact on Western Central African rainforests 2,600 y ago," by Yannick Garcin et al.
MEDIA CONTACT: Yannick Garcin, University of Potsdam, GERMANY; tel: 49-1636335348; e-mail: yannickgarcin@yahoo.fr
Journal
Proceedings of the National Academy of Sciences