Emergy-based accounting method for aquatic ecosystem services valuation: A case of China

The importance of aquatic ecosystem services (ES) has been widely recognized. However, complexities among different aquatic ecosystems, the uncertainties of ES delivery mechanism and the lack of a unified accounting method from a production perspective still bring challenges for assessing aquatic ecosystem services valuation (ESV). To address these three concerns, this study develops a coherent accounting method on aquatic ESV. This includes: (1) an aquatic classification system (“source”, “process” and “sink” type); (2) an aquatic ES classification system, which considers their formation mechanisms; (3) a set of detailed ESV accounting techniques. Aquatic ES are divided into direct services, indirect services and existing services. In addition, according to the characteristics and uniqueness of different aquatic ecosystems, the importance degree of each aquatic ES is identified. Further, the aquatic ESV accounting techniques are established to reach three study goals: (1) integration with the characteristics of specific aquatic ecosystems when measuring ESV, (2) aquatic ESV assessment from supply side, and (3) unified metric. The newly developed aquatic ESV accounting is applied to aquatic ecosystems as a case study to test this method. The results show that: (1) Sichuan has the largest aquatic ESV (1.12E+23 sej/yr); (2) Tibet has the largest aquatic ESV per unit area (5.55E+11 sej/m2/yr); (3) Most China's aquatic ecosystems have microclimate regulation as their largest ESV per unit area. This study can fill several research gaps on aquatic ESV evaluation, providing also scientific suggestions on differentiated conservation and management policies applied to specific aquatic ecosystems.