1. Royal Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, The Netherlands
2. Present address: Research Center Ocean Margins, University of Bremen, PO Box 330440, 28334 Bremen, Germany.

Correspondence to: Enno Schefu¹ Correspondence and requests for materials should be addressed to E.S. (e-mail: Email: schefuss@uni-bremen.de).

Abstract

The dominant forcing factors for past large-scale changes in vegetation are widely debated. Changes in the distribution of C₄ plants—adapted to warm, dry conditions and low atmospheric CO₂ concentrations¹—have been attributed to marked changes in environmental conditions, but the relative impacts of changes in aridity, temperature^{2, 3} and CO₂ concentration^{4, 5} are not well understood. Here, we present a record of African C₄ plant abundance between 1.2 and 0.45 million years ago, derived from compound-specific carbon isotope analyses of wind-transported terrigenous plant waxes. We find that large-scale changes in African vegetation are linked closely to sea surface temperatures in the tropical Atlantic Ocean. We conclude that, in the mid-Pleistocene, changes in atmospheric moisture content—driven by tropical sea surface temperature changes and the strength of the African monsoon—controlled aridity on the African continent, and hence large-scale vegetation changes.