Emergy and eco-exergy evaluation of wetland restoration based on the construction of a wetland landscape in the northwest Yunnan Plateau, China

Abstract The synthesis of emergy and eco-exergy is one of the most effective methods in the evaluation of wetland restoration. In this study, the landscape design for the restoration of Napahai wetland in the northwest Yunnan Plateau of China was carried out, and the sustainability and self-organizational level of the wetland before and after restoration were evaluated using eco-exergy and emergy combined with the Lorenz curve method. The results showed that wetland plants rapidly increased from 26 species to 52 species after two years, with a gradual decrease in pollutant-enduring species and the reappearance of the marsh plants Sparganium simplex and Batrachium bungei communities that had disappeared for many years, which speed up the succession and structure organization of the community. The wetland was better for biomass accumulation and soil improvement after restoration, and there were significant decreases in the concentrations of TP, TN and COD in the water body. The sustainability index values for the wetland ranged from 4.17 before restoration to 2385.16 after restoration, and the ecosystem service values for the wetland after restoration was 1.95 times higher than that before restoration. These results confirmed that the wetland after restoration was less environmentally stressed and more sustainable. In addition, the values of eco-exergy and specific eco-exergy after restoration were 1.70 and 1.01 times higher than that before restoration, respectively; the emergy/exergy ratio was lower for the wetland after restoration. These results suggested that the wetland after restoration had higher complexity and self-organizational level, and became a self-sustaining and resilient natural system. This study represents a new exploration of the emergy and eco-exergy evaluation on the wetland restoration, providing an engineering demonstration and a reference for the landscape design of wetland restoration in the plateau region.