Accelerated vegetation transformation in the World's highlands since the past 20 kyr

Growing evidence underscores fundamental differences in vegetation succession and fire dynamics between global highlands (>2000 m a.s.l.) and lowland regions, yet the temporal patterns and governing mechanisms of rates of vegetation compositional change (RoCs) in alpine systems remain poorly constrained. Through systematic analysis of 157 fossil pollen records and 143 charcoal sequences across six highlands (North America, Europe, Central Asia, South America, Africa and Tibetan Plateau), we identify two distinct phases of accelerated ecosystem reorganization: (1) an initial post-Last Glacial Maximum acceleration (∼18- ∼ 15 cal. Kyr BP) linked to postglacial recovery, and (2) a recent acceleration over the last millennium driven by anthropogenic landscape transformation. Structural equation modeling (SEM) reveals that RoCs drivers follow a tripartite climate-fire-human interaction pattern with marked regional disparities: fire effects depend on vegetation types and disturbance frequency; CO₂ fertilization is mediated by C₃/C₄ competition; and human activities progressively dominated late-Holocene dynamics via landscape structural modifications. This synthesis is the first to quantify the driving network of highland vegetation dynamics on a global scale through the integration of multiple indicators (pollen, charcoal) and SEM, providing paleoecological evidence for understanding the ecological vulnerability of alpine regions in the “Anthropocene”.