Review: Monitoring of land cover changes and plant phenology by remote-sensing in East Asia

To achieve a sustainable society and solve the problems caused by climate change and socioeconomic activities, it is necessary to monitor the spatial and temporal variability of ecosystem functions, services, and biodiversity at both regional and global scales. During the last decade, we have seen rapid and significant improvement in satellite and near-surface remote-sensing technologies. In this review, we describe how remote-sensing observations are being used to effectively evaluate the spatial and temporal variability of land use and cover types and of plant phenology in East Asia. We discuss the current status, uncertainties, problems, and future perspectives for terrestrial ecosystem and biodiversity monitoring, and we address the multidisciplinary research by incorporating in situ and satellite observations for East Asia. Recent satellites with advanced optical sensors, such as MultiSpectral Instrument/Sentinel-2A/2B, Advanced Himawari Imager/Himawari-8, and PlanetScope, and satellites with synthetic aperture radar, such as Advanced Land Observing Satellite-2, allow detailed monitoring of land use and cover type changes and plant phenology. These satellite sensors can provide images with high spatial (3-10 m) and high temporal (10 min to 5 days) resolution, at both large (>= 1 km(2)) and small (<1 km(2)) scales. In particular, researchers are expected to develop discrimination techniques that will enable these advanced satellite technologies to detect evergreen broadleaf trees and ways to estimate the geographic distribution of leaf traits. We encourage more collaborations among ecologists, engineers, and remote-sensing scientists to share their abundant knowledge and experience and thereby improve the monitoring capabilities.