Increasing Mortality of Rare Tree Species Amplifies Extinction Risk in Tropical Forests Under Climate Change

ABSTRACT Aim Global climate change has intensified the extinction risk of plant species in tropical forests. Yet, empirical validation of how individual species respond to climate change remains lacking, and the demographic mechanisms linking individual mortality to long‐term extinction risk are poorly understood. Location Panama, Central America. Time Period 1982–2100. Major Taxa Studies Woody plants. Methods Using replicated tree census data from 44 forest plots in Central American tropical forests, comprising > 400,000 individuals and > 130,000 records of rare species survival, we examined the mortality dynamics and extinction risk of rare plants under climate change through a spatially explicit, trait‐based forest dynamics model. Results We found that rare species exhibited consistently higher mortality than common species, driven jointly by climatic stress and biotic interactions. Specifically, mortality increased with warming, vapour pressure deficit and neighbourhood density, but decreased with individual basal area. Functional traits, particularly those related to hydraulics and structures, modulated species‐specific responses and vulnerability. Over the last two decades, rare species experienced an average loss of 16.8% per plot, with climate‐driven changes accounting for approximately one‐quarter of this loss. By 2100, depending on the climate scenarios, 53.3%–64.2% of native rare species are projected to be extirpated locally, and 9.4%–27.8% to become regionally extinct. Main Conclusions Our findings demonstrate that rare species face elevated mortality and accelerated extinction risk under climate warming, with functional traits playing an important role in shaping species‐specific responses. By linking individual demography, species traits and long‐term forest dynamics, this study provides a mechanistic framework for extinction risk assessments and highlights the need for trait‐informed conservation strategies to safeguard tropical biodiversity under climate change.