Spatial Decay and Landform Dependence of Conservation Spillover Around Karst Nature Reserves in Southern China

Nature reserves serve as core areas for maintaining ecological functions in karst regions, and their conservation efficacy and surrounding influence are crucial to ecological security. However, knowledge gaps remain regarding spillover effects, driving mechanisms, and key areas around nature reserves across landform types in the Southern China Karst. This study examines conservation effectiveness, spillover effects in surrounding buffer zones (5–10 km), and driving mechanisms across NRs of different landform types. Results show that ecosystem services decline along the gradient of “nature reserves–5 km buffer zone–10 km buffer zone”. The 5 km buffer shows stronger potential spillover patterns than the 10 km zone, particularly for carbon storage and soil conservation. The karst fault basin exhibits higher protection efficiency in the 5 km buffer zone than within nature reserves, indicating ecological feedback. Environmental variables are direct positive drivers of integrated ecosystem services; vegetation variables exert the strongest positive mediating effect via environmental variables; degradation variables show region-dependent mediating effects; and the negative direct effect of human-activity variables weakens with distance, alongside positive mediating effects. This study fills knowledge gaps concerning the spatial differentiation of conservation effectiveness and ecological key areas, offering support for ecological protection and restoration.