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Popular Archaeology Central African rainforests shrunk not solely because of climate change, suggests this new study. Scientists have long held that some of the rainforests of Central Africa disappeared about 3,000 years ago, abruptly replaced by savannas due to a dramatic shift in the regional climate. However, the conclusions of a recent study now suggest that it was not climate change alone that may have been responsible for the shift -- that humans may have had a big hand, as well. Germain Bayon and a research team of colleagues conducted a geochemical analysis of a marine sediment core taken at the mouth of the Congo River and determined that the sediment had undergone very significant chemical weathering around 3,000 years ago. While climate change at the time was a factor, the weathering also coincided with the arrival of Bantu-speaking farmers from the region that now encompasses modern-day Cameroon and Nigeria. These Bantu peoples, according to the researchers, brought their agriculture and iron smelting technologies with them, possibly contributing to and enhancing the changes that impacted the Central African rainforests. As they intensified their land use by cutting down trees to create arable land for agriculture and iron smelters, the ensuing erosion and effects on the climate helped to create a drier, more savannah-like landscape around 3,000 years ago, resulting in the conditions we see today. Reports Bayon, et. al., "evidence from our proxy record that chemical weathering rates at that time were unprecedented during the last 40 thousand years clearly suggest that the environmental impact of human population in the central African rainforest was already significant about 2500 years ago, at least greater than that induced by the Late Quaternary (the past 0.5-1.0 million years) climatic oscillations"[1]. This paper is published online by the journal Science, at the Science Express website, on Thursday, 09 February. Seehttp://www.sciencexpress.org. [1] "Intensifying Weathering and Land-Use in Iron Age Central Africa," by G. Bayon; B. Dennielou; J. Etoubleau; E. Ponzevera; S. Toucanne; S. Bermell at IFREMER in Plouzané, France. This work was sponsored by the French National Research Agency (ANR), via the ECO-MIST project.
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