In humid forests in Southeast Asia, hundreds of species from dozens of plant families reproduce synchronously at multi-year intervals. Dipterocarps and many other species that join general flowering events are undergoing dramatic environmental changes. Projecting future phenological changes is an urgent task for the management and conservation of tropical forests.
     Here, we analyzed historical records of reproductive phenology and climate data over 35 years in peninsular Malaysia and developed a predictive model that considers cool temperature and drought as proximate cues of flowering. More than 80% loss of mass flowering events was predicted by 2100 under the scenario of high CO2 emission compared to the low emission scenario. Species that are sensitive to low temperature for flowering were more vulnerable to climate change than drought-sensitive species. Different reproductive successes across dipterocarp species would alter forest regeneration and, eventually, plant species composition in the future. Furthermore, changes in the frequency and intensity of flowering will impact population dynamics of animals that rely on flowers and fruits. Enforcement of conservation, restoration, and management programs to protect the threatened forest are necessary to prevent tropical forest degradation.