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 concentrations (Collatz et al., 1998, doi:10.1007/s004420050468) -have been attributed to marked changes in environmental conditions, but the relative impacts of changes in aridity, temperature (Pagani et al., 1999, doi:10.1126/science.285.5429.876; Huang et al., 2001, doi:10.1126/science.1060143) and CO2 concentration (Cerling et al., 1993, doi:10.1038/361344a0; Kuypers et al., 1999, doi:10.1038/20659) 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.

mcd-scale after Jansen & Dupont (2001, doi:10.2973/odp.proc.sr.175.236.2001), Age after Dupont et al. (2001, doi:10.1130/0091-7613(2001)0292.0.CO;2)

Supplement to: Schefuß, Enno; Schouten, Stefan; Jansen, J H Fred; Sinninghe Damsté, Jaap S (2003): African vegetation controlled by tropical sea surface temperatures in the mid-Pleistocene period. Nature, 422(6930), 418-421