The current status, potential and challenges of remote sensing for large-scale mangrove studies

Large-scale mangrove studies are pivotal for coastal forest restoration and climate change mitigation as evidenced by an alarming fact that globally mangrove has declined more than 30% in the last 50 years. Consequently, such a rapid decline leads to 10% of the additional carbon emissions due to global deforestation. Remote sensing plays an indispensable role in studying large-scale mangroves. However, the status and evolution of how remote sensing helps large-scale mangrove studies have not been reported. More importantly, the potential and challenges of such studies are yet unveiled. To bridge these gaps, we investigated the evolutions, drivers, and future directions for remote sensing large-scale mangrove studies through a comprehensive literature review. We disclosed four key major research topics: extent delineation, vegetation structure, species composition, and ecological processes. Large-scale mangrove studies are still in their infancy, therefore, does not present distinctively chronological transitions as revealed by their counterpart in conventional mangrove studies. Although hardware and software advancements have made it viable to carry out large-scale mangrove studies, it is still challenging to culminate them, owing to the insufficient field samples and fine-resolution remote sensing imagery. Moreover, we found that topics exclusive to mangrove forests, such as outwilling, are still unexplored and waiting for further investigation.