A review of mangrove degradation assessment using remote sensing: advances, challenges, and opportunities

Mangrove ecosystems are essential coastal environments that provide extensive ecological and socioeconomic benefits to both human societies and the natural environment. However, mangrove degradation can lead to significant declines in biodiversity, ecosystem processes, and ecosystem services. Compared to the extensive research focused on documenting mangrove areal changes and deforestation, there is a lack of review on the current status of mangrove degradation identification with the assistance of remote sensing data. This review analyzed 104 papers focusing on remote sensing-based mangrove degradation assessments across tropical and subtropical regions from Web of Science and Google Scholar databases. We summarized the remote sensing approaches employed, the specific proxies or indicators derived from remote sensing data to characterize mangrove degradation, the primary remote sensing datasets utilized and remote sensing image classification methods. We also identified the key challenges (e.g. lack of optimal proxies, confusions between true degradation and natural variability) and emerging opportunities for future research in the remote sensing-based assessment of mangrove degradation. Based on publications, one of the primary challenges lies in the inconsistency of definitions and proxies used to characterize mangrove degradation. Scale effects and the inherent complexity of remote sensing data further compound these challenges. Nonetheless, the increasing availability of advanced multi-source remote sensing data holds promise for more accurate and comprehensive measurement of mangrove degradation, which could ultimately inform and guide sustainable coastal management and restoration efforts.