10-m-resolution mangrove map of China for 2017 derived from multi-source and multi-temporal satellite observations

Mangroves can provide a wide range of services, such as coastal protection, breeding and nursing grounds, carbon sinks. Mangroves in China have gradually recovered after strict protection and afforestation, however, the fragmentation in mangrove distribution that was resulted from long-term human disturbance has not been changed much. Thus, a detailed mangrove map is important for mangrove protection. Mangrove maps currently available for China were produced with 30-m-spatialresolution Landsat imagery. At this resolution, mangroves in narrow strips or small fragmented areas are difficult to capture. To solve the problem, we developed a 10-m-resolution mangrove map of China for the year 2017. We utilized Sentinel-1 SAR and Sentinel-2 MSI time-series images, together with AW3D30 terrain data. We first classified coastal land covers based on quantile synthesis; following this, the mangrove category was refined by applying the tidal flat constraint and manual editing. A pixel-based mangrove map (PXL_Map) was produced using the Google Earth Engine cloud computing platform. PXL_Map achieved an overall accuracy of 95.3 ± 0.2% based on validation samples, and a 91.6% accuracy based on 859 field sample plots. The maps produced in this study improved the delineation of small mangrove patches along tidal creeks relative to recent Landsat-based maps. Under Albers' Equal-Area Projection, the total mangrove area was estimated to be 21,148 ha, which is smaller than actual area because we did not repair the broken patches. The provided mangrove patches in China for 2017 can assist field surveys, remote-sensing-based mangrove monitoring, etc.