Climate extremes drive global reorganization of woody and herbaceous plants

Terrestrial ecosystem properties hinges on the functional equilibrium between woody and herbaceous plants, yet the climatic drivers of this balance remain poorly resolved. By constructing the global distribution maps for 349,000 vascular plant species, we demonstrate that extreme quarterly climate variables—rather than annual averages —primarily determine growth form distributions. Machine learning models reveal that woody plant dominance correlates with coldest quarter temperatures coupled with wettest quarter precipitation, whereas herbaceous prevalence associates with marked temperature seasonality and warmest quarter rainfall. Our models demonstrate that increasing temperature seasonality disproportionately disadvantages woody species while initially favoring herbaceous plants, and anthropogenic disturbances amplify these patterns—woody vegetation exhibits accelerated decline under intensive human pressure, whereas herbaceous species show positive responses to moderate disturbance levels. Climate projections indicate growth form reorganization across 63.8% of global ecoregions by 2060, with woody plants decreasing in 24.6% of ecoregions (particularly tropical rainforests) but expanding in 39.2% of ecoregions (notably temperate forests). These shifts inversely mirror herbaceous plant dynamics, with tropical rainforests—critical carbon sinks hosting Earth’s highest biodiversity—facing severe woody species reductions. The predicted contraction of woody dominance in these vital ecosystems signals potential destabilization of carbon sequestration capacity and species-rich habitats. Our analysis underlines climate-driven imbalances in plant functional strategies and the need for conservation frameworks that explicitly integrate growth form responses to climate variability.