Terrestrial ecosystems play crucial role in storing carbon and hence in regulating the atmospheric CO2. Carbon cycle in ecosystems is the combined phenomena of ecological, biogeochemical and meteorological processes. In order to reveal the ecological mechanisms of carbon cycling in terrestrial ecosystems and then to detect the current and future impacts of climate change in East Asia, we have established the "A3 Foresight Program (JSPS, NRF, NSFC)". Our research involves (1) ecological research such as plant biomass, plant ecophysiology and soil respiration measurements, (2) in situ and satellite remote sensing of canopy phenology, and (3) simulation models to integrate the ecological and micrometeorological process to assess spatial and temporal distributions of carbon cycling. This symposium aims to show our intensive and recent research outcomes by the multidisciplinary and international efforts, and to discuss the future needs in ecosystem science under climate change in East Asian region.