Influence of 1100 years of burning on the central African rainforest

Abstract

Four major forest types are currently present in the central African rainforest; mixed forest, Marantaceae forest, monodominant Gilbertiodendron forest and swamp forest. These forest types span vast areas and demonstrate highly significant differences in diversity and productivity; yet factors responsible for their formation are poorly understood. One hypothesis is that they are as a consequence of different intensities of past human activity, in particular burning. Here we present results from fossil charcoal contained in 12 sediment cores spanning the last 2500 yr and covering a spatial area of more than 900 km2. These records demonstrate that burning started in the last 1100 yr with areas currently covered by Marantaceae forest undergoing more frequent burning events than the other forest types. In comparison monodominant Gilbertiodendron forest appear to have undergone large burning events only in the past 200 yr. These records also demonstrate a lack of spatial relationship between fire events at the different sites (discontinuous and asynchronous) suggesting that these fires resulted from localised burning events probably caused by human ignitions. Whilst the large spatial scale of past human activities in the South American rainforest is now widely acknowledged, these results indicate, for the first time, the significant impact that early human populations had on the community composition of central African rainforest.