Integration of urban‒rural regional functions and their effects on CO2 emission in mountainous areas

Urban-rural regional function integration (URRFI) is closely linked to the sustainable development goals of eradicating poverty, particularly in mountainous areas. Achieving URRFI in these regions is critical for sustainable development. Nevertheless, the development mechanism of URRFI and the extent to which it may contribute to CO 2 emissions in mountainous areas remain unclear. Focusing on the western Hunan region of China, this study explores the development mechanism, the characteristics of URRFI, and investigates its impact on CO 2 emissions. As an ordinal parameter, the rural regional function drives the dynamic transformation of URRFI from an inefficient and disorderly state to an orderly and advanced state. URRFI progresses from the primary to the advanced stage, and the average value increases from 0.0937 to 0.8078. A nonlinear relationship is identified: CO₂ emissions rise when URRFI is below 0.2935 and decline once it exceeds this threshold. We present policy implications for adopting strategic of large villages and small towns to accelerate URRFI in mountainous areas, while prioritizing ecological and environmental protection. These implications derived from our study provide valuable reference for sustainable development strategies in mountainous regions of developing countries.