Fig. 4. Late Holocene, Middle Holocene and LGM patterns in latitudinal C₃ and C₄ vegetation distributions.

Plant-wax δ¹³C along the West African margin refs. ^{6,18,42,57,94,129–131} separated into late Holocene (2–0 ka, black diamonds), middle Holocene (8–6 ka, blue squares), and Last Glacial Maximum (23–19 ka, red triangles). Each transect is fit using a locally weighted scatter-plot smoothing (LOESS) function, (“smooth” function, MATLAB v2020a, see “methods” for details). The relative contribution of C₄ v. C₃ vegetation between intervals is shown in orange (greater C₄) and green (greater C₃) shading. a The effect of increased rainfall during the humid middle Holocene. b Middle Holocene – Late Holocene δ¹³C_wax anomalies calculated for each individual core c The effect of decreased atmospheric CO₂ during the LGM. d LGM – Late Holocene δ¹³C_wax anomalies calculated as in b.