Ecosystem service trade-offs upstream and downstream of a dam: a case study of the Danjiangkou dam, China

Studying the trade-offs and synergies between ecosystem services upstream and downstream of dams is of great importance because such studies can help guide the coordinated development of ecosystems. Taking the Danjiangkou dam as an example, we studied the trade-offs and synergies of ecosystem services in the river basin upstream and downstream of the dam. First, based on Costanza’s research method, we used the equivalent factor method to revise the equivalent factor of the Hanjiang River Basin. This basin includes the Danjiangkou dam, which provides services for agriculture. On that basis, the spatio-temporal dynamics of ecosystem service values during the period of 1990–2015 for the whole basin were estimated. The relationships among ecosystem services upstream and downstream of the Danjiangkou dam and throughout the basin were then analyzed using correlation analysis. The results demonstrate that the value of ecosystem services for the entire basin steadily increased during the period of 1990–2015. Among all ecosystem services, climate regulation and hydrologic regulation presented the highest ecosystem service values. Clear differences in spatial patterns existed in the two analysis areas. The ecosystem service values upstream of the dam were higher than those downstream of the dam. Approximately 60% of the relationships among the ecosystem services in the whole basin were synergistic, which was the dominant relationship. Synergies were more common upstream of the dam than downstream, and these synergies existed primarily between regulation services and composite services and between regulation services and cultural services. Trade-offs were more common downstream of the dam and existed mainly between supply and regulation services. Upstream food production was involved in significant trade-offs with biodiversity below the dam. Raw material production, gas regulation, climate regulation, soil conservation, and biodiversity above the dam showed significant synergies with gas regulation and climate regulation downstream.