Ancient deforestation in the green heart of Africa

The forested expanses of Central Africa host the second largest block of tropical rainforest on Earth (after Amazonia), stretching over around 2 × 106 km2. They are the great green heart of Africa, and changes in vegetation cover are likely to have important but poorly understood influences on the climate of much of the continent (1). A remarkable feature is that this blanket of forest appears quite tenuous—under the arid climates of the ice ages, the forest appears to have retreated into isolated pockets surrounded by savanna grasslands. Even in the climatically stable Holocene, there appears to have been periods of substantial forest retreat. In particular, there is evidence for a period of major forest loss between 3,000 and 2,000 y ago [termed the Late Holocene rainforest crisis (LHRC) (2)]. Attributing the cause of this decline is complicated by the fact that this period coincided with major expansion of Neolithic and early Iron Age farmers southward from the Nigeria/Cameroon border regions into western Central Africa. Did the farmers take advantage of a forest retreat driven by climate drying, or were they the primary cause of the forest loss? In recent years, there has been a vigorous debate on the cause of the LHRC. Now, Garcin et al. (3) provide new data and an unexpected new insight, presenting strong evidence that there was no strong drying event, and therefore suggesting that it was direct deforestation that caused this retreat of the Central African rainforests.Until a few years ago, there was a broad consensus among paleoecologists and archaeologists that that the LHRC was a climate-induced event, with humans playing a marginal role at most in enhancing forest loss. This view was based mainly on interpretation of vegetation pollen from lake cores and diatom data from marine cores, together … [↵][1]1Email: yadvinder.malhi{at}ouce.ox.ac.uk. [1]: #xref-corresp-1-1