Ecosystem service trade-offs and identification of eco-optimal regions in urban agglomerations in arid regions of China

Ecosystems play an essential role in maintaining biodiversity, regulating climate, and promoting functional biodiversity in arid urban agglomerations. Accurately assessing the characteristics of ecosystem services and identifying eco-optimal regions in urban agglomerations in arid regions are important for ecological security and the sustainable development of regional ecological systems. In this study, the ecosystem service functions of Urban Agglomeration on the Northern Slope of the Tianshan Mountains (UANSTM) were evaluated using the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model based on the Geographic Information System (GIS) platform coupled with multi-source data. Moreover, the eco-optimal regions were identified by the Ordered Weighted Average (OWA). The findings demonstrate that the development and ecological construction of the UANSTM lead to the conversion of a large amount of unused land to grassland, cultivated land, and construction land. Analyzing the relationship between ecosystem services and land types shows that the high value ecosystem services are mainly distributed in forest land and grassland. In terms of changes in ecosystem services, the net primary productivity (NPP) and habitat quality (HQ) values increased, while the value of soil retention (SR) and water yield (WY) decreased. The relationship between ecosystem services is mainly pairwise synergy, except for HQ-WY and NPP-WY. Regarding spatial distribution, the trade-offs and synergies of ecosystem services demonstrated different geospatial heterogeneity. The OWA model was employed to establish different risk values and weights to simulate different risk scenarios. The area of coverage of risk scenario 5, with the highest trade-off values, was selected as the eco-optimal region. The eco-optimal regions were mainly located in the urban agglomeration's central and southwestern high-altitude areas, where a safety barrier was established for the ecological region. The results of this study can serve as a reference for the ecological construction, land planning, and management of urban agglomerations in arid regions.