Effects of Freshwater Releases on the Delivery of Ecosystem Services in Coastal Wetlands of the Yellow River Delta Using an Improved Input-State-Output Approach

Abstract

Environmental flows play an important role in sustaining or enhancing ecosystem services provided by wetlands. In this study, using an improved input-state-output approach, we evaluated ecosystem service values to assess the ability of freshwater releases to improve the ecosystem of China’s Yellow River Delta Wetlands. We used emergy analysis to value the inputs, state, and outputs of the ecosystem services from 2001 to 2008, which covered the periods before and after the freshwater releases. From 2001 to 2004, the total emergy input increased from 8.50 × 1019 sej to 10.6 × 1019 sej, and then decreased to 6.30 × 1019 sej in 2008. From 2001 to 2008, the emergy output increased from 9.17 × 1022 sej to 10.6 × 1022 sej. The emergy yield ratio, representing the ability to supply ecosystem services per unit of inputs, increased by 71.3 %. The results show that freshwater releases improved provisioning, regulating, and cultural ecosystem services from the coastal wetlands. The environmental sustainability index, representing the sustainability of environmental development, decreased from 25.9 × 104 in 2001 to 1.74 × 104 in 2008; both values are much higher than normal for human-dominated ecosystems, indicating that the wetland is still predominantly natural. These results can guide managers in a more holistic evaluation of freshwater releases to support ecosystem restoration.