Spatiotemporal Dynamics and Scenarios Analysis on Trade-offs between Ecosystem Service in Three Gorges Reservoir Area: A Case Study of Zigui County

The Three Gorges Reservoir Area is an important and fragile ecosystem. Zigui County located in the heart of Three Gorges Reservoir Area, is facing a series of ecological threats including water and soil loss, as well as ecosystem degradation due to intensive anthropogenic interference and rapid urbanization. Thus, it is urgent to study the changes in ecosystem services and the dynamics of trade-offs, to find a strategy for optimization of regional ecosystem services. In this study, the spatial-temporal dynamic characteristics and trade-off relationships of the three ecosystem services, namely water yield (WY), carbon storage (CS), and soil conservation (SC) were firstly evaluated for Zigui County. The production possibility frontier (PPF) curve was used to determine the optimal development model for describing the trade-off characteristics among ecosystem services under the three scenarios. These were the business-as-usual scenario (BaU), ecological protection scenario (EP), and comprehensive development scenario (CD). The results show that: (1) all the three ecosystem services displayed spatial-temporal heterogeneity. From 2005 to 2015, CS increased by 2.20%, SC increased by 15.13%, while WY originally increased and then decreased. In a spatial sense, the highest values of WY were mainly distributed in the south of the county, the highest values of CS were distributed in the northeast and southeast, and the highest values of CS were distributed in the northwest and south. (2) CS-WY and SC-WY both showed significantly trade-off relationships, however, the relationship between CS and WY was stronger. Overall, the intensity of trade-offs was scale-dependent. (3) the relationships among the ecosystem services were closer to the PPF curve under CD, indicating that the allocation of land use is better under CD scenario. Therefore, future ecological management should simultaneously consider ecological security, food security, and economic and social development when formulating ecological protection and restoration measures for promoting the coordination of ecosystem services.