Significant greening of China’s mangrove forests during the last three decades

• kNDVI was used to monitor greening tendency of China’s mangrove forests. • During 1993 to 2022, China’s mangrove forests were significant greening. • Densely distributed mangroves were found with more pronounced greening tendencies. • The greening was positively related with sea surface salinity and air temperature. In recent decades, China’s mangroves have experienced severe degradation, followed by significant initiatives aimed at conservation and recovery. These initiatives have brought about significant changes in the extent of mangrove areas and their health conditions. Previous research has primarily concentrated on the dynamics of mangrove areas. Few studies have addressed the health condition, limited by lower spatial resolution, short time spans, and saturation effects of traditional vegetation indices. To overcome these challenges, we leveraged 37,144 Landsat scenes from 1993 to 2022 to generate kernel normalized difference vegetation index (kNDVI) images, monitoring spatial and temporal progression of mangrove greenness by kNDVI dynamics. Additionally, we analyzed the driving forces of kNDVI changes and environmental factors. The results showed that: (1) China’s mangroves’ kNDVI values were increasing obviously during the last three decades, which indicated significant greening trends; (2) mangroves with greening tendencies were predominantly found in densely distributed regions, whereas degradation occurred in dispersed and isolated mangroves; (3) in general, mangrove greenness was positively correlated with sea surface salinity ( r = 0.540, p < 0.01) and air temperature ( r = 0.488, p < 0.01). This study considered the spatial–temporal distribution characteristics of China’s mangroves, analyzed changes in their greening trends using kNDVI. The results and discussion could offer scientific references for the protection, restoration, and management of China’s mangroves, potentially helping to address challenges posed by changes in terrestrial and marine environments.