Half‐Century Loss and Transformation: Dramatic Spatio‐Temporal Evolution of China's Tidal Wetlands Ecosystem Revealed by Satellite Observations (1972–2025)

Anthropogenic activities and natural processes have accelerated the degradation of China's coastal tidal wetlands in recent decades. Quantifying long‐term spatio‐temporal evolution of these wetlands is critical for informing coastal conservation. While prior studies have documented spatio‐temporal evolution in China's tidal wetlands, a comprehensive analysis spanning China's entire coastline over a half‐century period (1972–2025) remains unquantified. Therefore, in this study, by leveraging long‐term Landsat images (1972–2025) and a frequency statistics method, we quantified the evolutionary trajectories of tidal wetlands over the period 1972–2025 from macro‐scale to micro‐scale. Results showed that: (1) China's existing tidal wetlands covered an area of 8995 km 2 in 2025, primarily located in the coastal provinces of Jiangsu, Shandong, Liaoning, and Fujian. Spatially, their distribution showed a marked north–south disparity, with greater coverage in the northern regions. (2) From 1972 to 2025, China's tidal wetlands had experienced a substantial net loss of 45%. Tidal wetlands' area had decreased in all coastal provinces and municipalities except Shanghai, with Tianjin showing the most dramatic reduction (78%). Furthermore, landward boundaries had demonstrated significantly greater change intensity than seaward margins. (3) The tidal wetlands of the Jiangsu Radial Sand Ridges had maintained relatively stable areal extents and experienced slow spatial changes. In contrast, the tidal wetlands of Bohai Bay had shown substantial reductions in total area. Concurrently, their landward boundaries had undergone progressive seaward shifts, fragmenting once‐contiguous wetlands into isolated patches, while seaward boundaries had been alternately influenced by erosion and sedimentation processes. This study provides a robust scientific foundation for evidence‐based management and strategic planning of coastal zones in China.