Coastal wetland restoration framework based on hydrogeomorphic units of the coastal wetland of Yancheng, China

Effective implementation of restoration projects is essential to solving the degradation of coastal wetlands. Due to the lack of systematic guidance or unsuitable engineering measures, some coastal wetland restoration projects have suffered from lower-than-expected results and poor sustainability. Therefore, it is necessary to construct a regional-scale wetland restoration framework from a macro perspective prior to project implementation, which can guide pre-study and follow-up restoration practices. In this study, the hydrogeomorphic units (HGUs) of Yancheng coastal wetlands were delineated according to the regional hydrogeomorphic conditions, and the changes in land use/cover and hydrological connectivity of each HGU from 1980 to 2019 were analyzed. The results showed that the area of natural wetlands in the study area declined rapidly, with a decline of 48.38%, and was mainly converted to aquaculture ponds or farmland during the 40 years. The structural complexity and transport capacity of tidal creeks decreased significantly, which indicated that the hydrological connectivity decreased. The main problems of degradation in the region were the reduction of large areas of natural wetlands, the rapid expansion of exotic species, and the decline in hydrological connectivity, etc. Combining the degradation problems and the restoration objectives, feasible strategies and methods were selected for different types of HGUs from both active and passive restoration categories, thus forming a coastal wetland restoration framework for the Yancheng coastal wetlands based on HGUs. This study takes regional hydrogeomorphology as the antecedent context condition, and the idea of a systematic restoration framework constructed by combining landscape perspectives can provide scientific support for wetland restoration practice.