Ecosystem service evaluation and optimisation in the Shule River Basin, China

Abstract

The water resources in the arid regions of Northwest China are scarce, and the ecological environment is fragile. Therefore, the evaluation and optimisation of ecosystem services (ESs) in these regions are key to regional ecological security and sustainable development. Few previous studies have incorporated trade-offs and synergies between services provided by various ecosystems into optimal scenario setting constraints. Here, considering the Shule River Basin (SRB) as a typical arid area, we evaluated four ESs, including net primary productivity (NPP), soil conservation (SC), sand retention (SR), and water yield (WY), from 2001 to 2018, and explored their spatiotemporal characteristics. Combining the synergy of ESs and ecological environment protection objectives of the basin, we designed three optimisation scenarios, namely ‘maximum probability of land use suitability’ (S1), ‘increase in NPP without decrease in WY’ (S2), and ‘increase in NPP without decrease in SC and SR’ (S3), based on the cellular automata model to optimise ESs. The four ESs in the SRB showed fluctuating but increasing temporal trends, with the increase in NPP being the most obvious. Moreover, the four ESs exhibited obvious spatial heterogeneity. WY showed synergistic relationships with the other three services, and these relationships became stronger over time. In S1, SC increased, whilst NPP, SR, and WY decreased; in S2, the four ESs increased; and in S3, NPP, SC, and SR increased, whilst WY decreased slightly. Based on the trade-off and synergy of optimised ESs, the scenarios (S2 and S3) in which the services in synergy with NPP do not decrease can improve the ESs as well as weaken the trade-off and strengthen the synergy between them. These findings are used for stakeholders to deepen their understanding of the future consequences associated with today’s human activities and decisions, against a range of possible outcomes.