Spatiotemporal Evolution of Global Vegetation Since the Last Glacial Maximum: Insights from Quantitative Pollen Reconstructions

How global vegetation responded to climate change since the Last Glacial Maximum (LGM) remains incompletely understood due to the lack of continuous, global-scale reconstructions. Here we present a millennial-resolution reconstruction of global vegetation patterns since the LGM based on a synthesis of 3,286 pollen records using a biomization framework. We show that tundra dominated the mid- to high-latitudes of the Northern Hemisphere during the LGM, while steppe and open coniferous forests characterized western North America, taiga prevailed in eastern North America, and extensive steppe covered much of Eurasia. In the tropics, rainforest extent was markedly reduced, accompanied by widespread expansion of arid shrublands across Africa.

We find that forest expansion following deglaciation was spatially asynchronous across latitudes and hemispheres. Global forest cover increased by ~31% from the LGM to the mid-Holocene, before declining by ~5% during the late Holocene. In the Northern Hemisphere mid- to high-latitudes, forest cover rose rapidly after the LGM, peaked between ~7 and 5 ka BP, and subsequently declined, whereas Southern Hemisphere mid-latitudes experienced a more gradual increase, reaching maximum forest extent earlier (~12–8 ka BP) and remaining relatively stable thereafter. Tropical regions exhibited the most heterogeneous trajectories, with early deglacial fluctuations, sustained expansion to a mid-Holocene maximum (~6–4 ka BP), and enhanced variability in the late Holocene.

Our results reveal pronounced asynchrony in global vegetation evolution and provide a biome-scale perspective that refines previous global reconstructions. This dataset establishes a benchmark for evaluating palaeovegetation simulations and offers new constraints on vegetation–climate feedbacks relevant to future ecosystem change.