The impact assessment of hydro-biological connectivity changes on the estuary wetland through the ecological restoration project in the Yellow River Delta, China.

Yellow River Delta (YRD) is one of the youngest delta with complex hydrological and biological connectivity in the world, where offers habitats to the famous waterfowls in the Eastern Asia. Meanwhile, one specific ecological restoration project named as the "Wuwanmu" and followed by the "Shiwanmu" within the National Nature Reserve of the Yellow River Delta (NNRYRD) complicated the hydrological and biological connectivity. How to quantitatively evaluate the extent of coastal wetland affected by the project will be a difficult problem. Hence the authors presented three innovative models of the Marine Connectivity Change Index (MCCI), the Coupling Index of Hydro-biological Connectivity (CIHBC), and the Assessment Index of Suitability on Bird Habitats (AISBH). After the project, the habitat of Phragmites australis has been restored effectively with the increased area of 24.59%, while the habitat of Suaeda salsa as the native species lost largely with decreased area of 84.62%. And the tidal channel having been cut off by the project resulted in isolating the buildup restoration area from seawater, and reshaping completely the plant habitat environment. So the hydrological and biological connectivity has been changed largely with the 47.79% decreased MCCI area and the 16.3% decreased zero-valued CIHBC area. However the AISBH non-zero-valued area increased 10.7%, and with the hidden worry of the decreased Grallatores number. From the connectivity prospective, three models presented a significant methodology to evaluate the complex impact on the estuary wetland habitat caused by the restoration project. In the long run, the ecological impacts should be highlighted to the change of tidal channel and the corresponding tidal issues, and the continuous and big loss of native plant spices such as S. salsa. The further study needs to explore the longer-term assessment of the ecological restoration project and its multiple effect in the future.