Unfolding the spatial spillover effect of urbanization on composite ecosystem services: A case study in cities of Yellow River Basin

River basins play an important role in national economic development and ecological security and can be well expressed by ecosystem services (ESs) research. Due to rapid population growth and climate change, it has had a significant impact on the ecosystem of the Yellow River Basin (YRB). Although ESs have been assessed in several studies, few studies have used a composite ecosystem service index (CESI) in their assessment. Thus, here, based on the InVEST model, bivariate spatial autocorrelation, and spatial econometric model, we studied the composite ESs in the YRB, with an aim to build a CESI for evaluating the overall ESs in the YRB. We found that the CESI of the YRB from 1990 year–2020 year had an obvious spatiotemporal distribution law at the city level and grid scale, showing a high distribution characteristic in the southeast. The spatial trend also showed a significant difference in regional distribution. There was a positive spatial correlation between the CESI and urbanization indicators that reflected the level of urbanization, and the distribution of the aggregation type among the three was similar. Furthermore, population density had a strong positive spillover effect on the CESI, whereas economic density and land development had a negative spillover effect. Therefore, the YRB should pay attention to transforming the extensive development model and paying attention to the negative spillover effect of economic density when laying out industrial structures. Additionally, it is necessary to control the expansion of built-up land and improve land use efficiency, thereby reducing the negative spillover effect of land development. This study’s findings can serve as reference for policy formulation in major river basins worldwide.