Highlights What are the main findings? A minor 1.37% proportion loss in high-ecological value of grassland, woodland, wetland, and water body caused a large ESV loss of CNY 116.141 billion. The negative contribution of precipitation and human activities to ESV is gradually weakening, while the promoting effect from both is strengthening. What are the implications of the main findings? Small losses of high-ecological-value land leading to large ESV declines highlight the priority of conserving these land types in policy-making; quantifying ESV losses also supports ecological compensation standards in fragile regions. As precipitation and human activities shift to exert positive impacts on ESV, this change supports the transition of regional environmental governance from passive restoration to active enhancement.Highlights What are the main findings? A minor 1.37% proportion loss in high-ecological value of grassland, woodland, wetland, and water body caused a large ESV loss of CNY 116.141 billion. The negative contribution of precipitation and human activities to ESV is gradually weakening, while the promoting effect from both is strengthening. What are the implications of the main findings? Small losses of high-ecological-value land leading to large ESV declines highlight the priority of conserving these land types in policy-making; quantifying ESV losses also supports ecological compensation standards in fragile regions. As precipitation and human activities shift to exert positive impacts on ESV, this change supports the transition of regional environmental governance from passive restoration to active enhancement.Abstract The spatiotemporal evolution of ecosystem services has a profound influence on the fragile eco-environment in Inner Mongolia and the arid/semi-arid and the ecological barrier regions of Northern China; in particular, the small-scale and high-value land variables may lead to large eco-environment effects through altering the ecosystem services, which is still unclear in this vulnerable area. The differential driving mechanism of both human activities and natural factors on ecosystem services also needs to be revealed. To solve this scientific issue, the synergistic methodology of spatial analysis technology, the improved ecosystem service assessment method, flow gain/loss model, global/local Moran's I approach, and the Geographically and Temporally Weighted Regression (GTWR) model were applied. Our main results are as follows: remote sensing monitoring showed that the land changes featured a persistent expansion of cropland and built-up areas, with a decline in grassland and wetland, along the east-west gradient from forests, grasslands, and unused-lands, to become the dominant cover type. According to our improved model, the ecosystem services considering the internal structure of build-up lands were first investigated in this ecologically fragile area of China, and the evaluated ecosystem service value (ESV) reduced from CNY 5515.316 billion to CNY 5425.188 billion, with an average annual decrease of CNY 3.004 billion from 1990 to 2020. Another finding was that the small-scale land variables with large ecological service impacts were quantified; namely, the proportion of grassland, woodland, wetland, and water body decreased from 62.71% to 61.34%, with only a relatively minor fluctuation of -1.37%, but this decline resulted in a large ESV loss of CNY 116.141 billion from 1990 to 2020. From the driving perspective, the temperature, digital elevation model (DEM), and slope exhibited negative effects on ESV changes, whereas a positive association was analyzed in terms of the precipitation and human footprint during the studied period. This study provides important support for optimizing land resource allocation, guiding the development of agriculture and animal husbandry, and protecting the ecological environment in arid/semi-arid and ecological barrier regions.