Rapid retreat of marsh-edge cliffs, Jiangsu coast, China

Coastal salt marshes are an essential part of the ecosystem, but they are threatened by marsh-edge cliff retreat. Using satellite remote sensing and field data from 2013 to 2017, this study investigates the exceptionally high retreat rates of marsh-edge cliffs along the central Jiangsu coast of China, averaging 24.6 m/a (range: 7.3–39.2 m/a), which are an order of magnitude higher than typical global values. We examine the temporal and spatial patterns of cliff retreat and explore the mechanisms driving these rapid changes. Previous studies have widely considered wave power as the primary driver of marsh-edge retreat; however, this study shows that it cannot fully explain the observed rates. We identify two key factors contributing to the rapid retreat: (1) the open tidal flat environment, where strong tidal and coastal currents transport eroded sediment away, hindering sediment replenishment, and (2) the relatively tall marsh-edge cliffs with a substantial mesotidal range (∼3.4 m), which are more susceptible to erosion through cantilever failure and slumping. These findings highlight the complex interplay of environmental factors driving marsh degradation and suggest that future research should incorporate high-temporal-resolution monitoring to better capture the nature of cliff erosion, especially with increasing changes in climate condition globally.