Pleistocene drivers of Northwest African hydroclimate and vegetation

Savanna ecosystems were the landscapes for human evolution and are vital to modern Sub-Saharan African food security, yet the fundamental drivers of climate and ecology in these ecosystems remain unclear. Here we generate plant-wax isotope and dust flux records to explore the mechanistic drivers of the Northwest African monsoon, and to assess ecosystem responses to changes in monsoon rainfall and atmospheric pCO(2). We show that monsoon rainfall is controlled by low-latitude insolation gradients and that while increases in precipitation are associated with expansion of grasslands into desert landscapes, changes in pCO(2) predominantly drive the C-3/C-4 composition of savanna ecosystems. Plant-wax isotope and dust flux records reveal that the long-term variability of the Northwest African monsoon is controlled by tropical solar radiation gradients. Grasslands expand into the Sahara during strong monsoons, but the ultimate composition of the ecosystem is controlled by CO2.

Automated summary

This study uses plant-wax isotope and dust flux records to reveal that the long-term variability of the Northwest African monsoon is controlled by tropical solar radiation gradients. While increases in monsoon rainfall are associated with the expansion of grasslands into desert landscapes, the composition of the savanna ecosystems is predominantly driven by changes in pCO(2).