Urbanization and ecosystem services: A spatiotemporal exploration in the Sichuan Portion of the Yellow River Basin

The upper reaches of the Yellow River in Sichuan Province are critical area for water conservation and ecological protection in China. However, they are experiencing a range of ecological and environmental challenges, including grassland desertification, wetland degradation, and soil erosion, all of which pose significant threats to the environmental sustainability and overall development of the Yellow River Basin. Urbanization can lead to irreversible damage to ecosystems. Therefore, understanding the relationship between urbanization and ecosystems is crucial for fostering sustainable development in the region. With land use and meteorological data in the upper reaches of the Yellow River in Sichuan Province in 2000-2020, and using InVEST model and standardized processing methods, we analyzed the spatiotemporal evolution characteristics of urbanization and four ecosystem services: water conservation, carbon storage, habitat quality, and soil retention. Additionally, we employed the GeoDa bivariate spatial autocorrelation analysis model to reveal the spatial correlations and interactions between urbanization and ecosystems. The results reveal a significant spatial mismatch between urbanization and ecosystem services in the upper Yellow River region of Sichuan Province. While the composite urbanization index decreased from 0.0075 to 0.0042 and remained concentrated in county centers, all ecosystem services showed improvement: water conservation increased from 17.38×10⁹ mm to 23.37×10⁹ mm, carbon storage rose from 936.60 Tg to 938.42 Tg, habitat quality improved from 0.875 to 0.879, and soil retention enhanced from 13.56×10⁸ t to 17.59×10⁸ t. However, these ecological gains were mainly driven by restoration in non-urban southern areas, creating a clear spatial disconnection from urban centers and leading to persistently weak and declining coordination between systems. This spatial decoupling underscores the inadequacy of the current urbanization model in promoting regional ecological synergy. We therefore recommend implementing differentiated zoning strategies: promoting compact development coupled with ecological restoration in county centers, strictly protecting core water conservation and carbon sequestration areas in the southern key ecological zones, and enhancing soil-water conservation and ecological restoration in the vulnerable northern belt, so as to establish an ecological security framework compatible with sustainable urbanization.