Background Bayannur city, situated in the western part of Inner Mongolia Autonomous Region at the apex of the Yellow River's "几"-shaped bend, serves as a critical safeguard for water ecological security in the middle and lower reaches of the Yellow River. Characterized by diverse ecosystem types, it holds an irreplaceable strategic role in advancing ecological conservation and high-quality development across the Yellow River Basin. Investigating the spatiotemporal evolution patterns and driving mechanisms of land use and ecosystem service values in this region carries significant implications for guiding sustainable land resource management and ecological protection initiatives in mid-basin cities of the Yellow River.

Methods Based on five-period land use datasets (2000 to 2020) of Bayannur city, this study employed an integrated approach combining land use transition matrix, ecosystem service value (ESV) equivalent factor method, global spatial autocorrelation analysis, and trade-off and synergy degree (TSD) model to investigate the spatiotemporal dynamics and influencing factors of ESV under land use changes at a 3 km × 3 km grid scale.

Results 1) From 2000 to 2020, grassland, desert, and cultivated land accounted for the highest proportions (totaling approximately 97%) and were distributed across northeastern, northwestern, and southern regions of Bayannur city. Over the 20-year period, the grassland area decreased by 10%, with the reduced grassland areas being converted into desert and cultivated land. Meanwhile, the areas of other land types increased. 2) The total ESV demonstrated a trend of initial increase followed by decline. Over the first decade, ESV increased by 3.441*10⁸ Yuan, while it decreased by 11.308*10⁸ Yuan in the subsequent decade. Grassland’s ESV constituted the largest proportion, with an annual average contribution of approximately 77%, and its trend mirrored the changes in grassland area. Hydrological regulation services (24%) formed the primary components of the city’s ESV. Over the 20-year period, food production services increased by 159*10⁶ Yuan, while all other ecosystem service categories experienced declines. 3) The spatial distribution of ESV showed significant temporal variability. After 2000, both the value classes and clustering patterns of ESV gradually became more spatially dispersed, accompanied by an increase in spatial fragmentation. 4) From 2000 to 2020, the relationships among ecosystem services in Bayannur city were predominantly synergistic, except for a strong trade-off between food production and other ecosystem services. 5) The reduction in grassland area was one of the key factors contributing to the decline in total ESV and the spatial fragmentation across the city.

Conclusions The study area should prioritize expanding forestland and grassland coverage to enhance regional ESV. The findings of this research provide critical insights for cities in the middle reaches of the Yellow River Basin to advance the realization of eco-product value.