Cross-scale spillover of ecosystem services reveals pathways for equitable ecological compensation in inland river basins.

Arid inland river basins face growing ecological pressure under climate change and intensive human activity, resulting in severe mismatches between ecosystem services (ESs) supply and demand. Using the Tarim River Basin (TRB) as a case, this study develops an integrated mass-to-value framework and spatial modeling approach to evaluate spatiotemporal dynamics, cross-scale spillovers, and horizontal ecological compensation (EC) for five ESs-water yield (WY), windbreak-sand fixation (SF), habitat quality (HQ), carbon sequestration (CS), and soil retention (SC)-from 2000 to 2023.Results show that total supply values rose from Chinese Yuan (CNY) 1.0 × 10¹¹ to 2.1 × 10¹¹, with SF increasing by 228.13 × 10³ CNY·km^-2 and WY by 1.44 × 10³ CNY·km^-2. Demand also climbed substantially, particularly WY and CS, yeqt persistent deficits remained, with average supply-demand ratios for SC and SF staying negative. Breakpoint and potential-field models revealed two spillover corridors-from Kizilsu to Kashgar and from Hejing to Luntai-while strong bidirectional flows connected the TRB with Tibet and Qinghai. EC simulations indicated downstream counties transferred > CNY 3.0 × 10¹⁰ annually to upstream and montane zones, with cumulative receipts above CNY 8.0 × 10¹⁰ in Hejing and Wuqia. Structural equation modeling identified temperature and evapotranspiration as dominant negative drivers, while NDVI and moderate human interventions exerted positive effects. Unlike previous studies limited to single services or local contexts, this research integrates multi-service and cross-scale spillover analysis with compensation modeling in a large arid basin. The framework provides novel insights into ES imbalance mechanisms and practical guidance for compensation design. It offers a transferable methodology with broad implications for sustainable resource governance in arid inland river systems worldwide.