A million-year record of fire in sub-Saharan Africa

Biomass burning today constitutes approximately one-third of annual anthropogenic CO2 emissions, and there is a sound theoretical base for expecting fire-related changes in vegetation patterns to affect climate, at least on a regional scale1,2,3. But despite the central role that fire has played in moulding many modern ecosystems, there is little information on the incidence of fire before the earliest time at which anthropogenic burning may have significantly affected natural fire regimes. Here we present a million-year record of elemental carbon abundance from marine sediments on the Sierra Leone rise, ‘downwind’ of sub-Saharan Africa. Elemental carbon serves as a proxy for wind-blow debris derived from the combustion of sub-Sahara vegetation. The inferred fire incidence in the region was low until about 400,000 years ago, but since that time intense episodes of vegetation fires have occurred during periods when global climate was changing from interglacial to glacial mode. The occurrence of a peak in elemental carbon abundance within the present interglacial is unique in the past million years, suggesting that this peak is anthropogenic in origin, and that humans have exercised significant control over fire regimes in the region at least since Holocene times.