Loss of tidal creek ecosystem vitality caused by tidal flat narrowing on the central Jiangsu coast, China

Globally, tidal flats are increasingly narrowing due to continuous reclamation and sea level rise. Nonetheless, the impact of tidal flat narrowing (TFN) on tidal creek systems that play a crucial role in the formation and shaping of tidal flats is not well understood, despite a cognition that the tidal flat-creek system is integrated and coevolved. In this study, based on the quantification and mapping of tidal creek ecosystem vitality (TCEV), we detected the state evolution of tidal creek systems in response to TFN process on the central Jiangsu coast (CJC), China. The results showed that two thirds of the original tidal flat width was lost from 1984 to 2020, with a narrowing rate of 210.9 m/yr. The seaward movement of seawall lines and the landward movement of low tide lines contributed 82.5 % and 17.5 % to this serious TFN process, respectively. Across the study period, the overall TCEV lost 82.3 % with a substantial transformation from high level to low level. In terms of three dimensions of structural complexity, functional integrity and spatial occupancy, the tidal creek system of CJC has greatly deviated from the high-quality state in 1984, which was significantly associated with TFN. For a natural mature tidal flat, the loss of its initial width seems acceptable when <1/3, but unacceptable when >1/2, which are two important thresholds corresponding to the lower and higher loss of TCEV, respectively. It is worried that the CJC tidal flat-creek system would fall into a vicious circle of state evolution. Therefore, efforts should be made to control irrational reclamation and perform ecological restoration based on an insight into the relationship between TCEV and TFN.