CLIMATE-VEGETATION MODEL SIMULATIONS OF AFRICA DURING GLACIAL AND INTER-GLACIAL PERIODS: IMPLICATIONS FOR TRANS-AFRICAN MIGRATION

A fully-coupled General Circulation Model (HadCM3LC) was used to simulate vegetation cover under two climate scenarios: pre-Industrial or typical inter-glacial climate boundary conditions and the Last Glacial Maximum (LGM). The model simulated only minor changes in rainforest cover, vegetation height, canopy architecture and productivity during the LGM which starkly contrasts with other African simulations using standard GCMs. The fully-coupled GCM takes into consideration vegetation feedbacks onto climate, and therefore incorporates the recycling of water through evapotranspiration and the preferential partitioning of surface energy into latent versus sensible heat. With respect to animal (human) migrations across Africa during the Pleistocene, inter-glacial climate-vegetation feedbacks result in an almost complete barrier between the north and south, with only the eastern outer edges of the central African rainforest becoming more accessible (i.e. less dense) to migration during peak glacial climate-vegetation conditions. The phylogenetic record of forest-dwelling and savannah-dwelling organisms is considered with respect to these scenarios to assess the likelihood of restricted north-south continental migration for most of the Pleistocene.