Climate change drove Late Miocene to Pliocene rise and fall of C₄ vegetation at the crossroads of Africa and Eurasia (Anatolia, Türkiye)

Abstract. Life on Earth has been capitalizing on the C₃ photosynthetic pathway for 2.8 billion years. However, in the world’s grasslands that emerged since the Paleogene, C₄ vegetation expanded dramatically between 8 and 3 Ma in response to climatic changes. Here we present the first comprehensive Late Miocene to Holocene δ¹³C soil carbonate record from the Eastern Mediterranean region (Anatolia) to reconstruct long-term geographic distributions of C₃ and C₄ plants, a region with patchy records compared to parts of Africa and Asia. Our results show a colonization of Anatolian floodplains by C₄ biomass by 9.9 Ma, similar to regions in NW and E Africa, followed by a transition from this mixed C₃-C₄vegetation to C₄ dominance between ca. 7.1 Ma and 4.9 Ma. The transition coincides with a similar shift from C₃ to C₄ vegetation in southern Asia and is generally attributed to the Late Miocene Cooling in response to decreasing atmospheric pCO₂. However, the Anatolian paleoecosystem patterns are unique due to a rapid and permanent return to C₃ dominance in the Early Pliocene, which is not observed elsewhere and occurs simultaneously with the disappearance of the open environment-adapted large mammal Pikermian chronofauna. We propose that this return to C₃ vegetation was caused by paleoclimatic processes that regionally shifted precipitation from the warm to the cool season, resembling the modern Mediterranean climate. In conclusion, changes in rainfall seasonality under subhumid climate, rather than increased aridity, drove the demise of C₄-dominated floodplains and the open-environment adapted Pikermian chronofauna at the Eurasian-African crossroads.