Landscape fragmentation exacerbates social-ecological system degradation in the Qinling Mountains by weakening ecosystem services

• Landscape fragmentation in Qinling Mountains is comprehensively mapped by PCA. • The social-ecological system network is established and its attributes are quantified. • Connectivity is the attribute most strongly affected by landscape fragmentation. • Soil conservation and net primary productivity are key elements in maintaining the stability of social-ecological system. Landscape fragmentation poses a significant threat to natural habitats and human well-being, hindering the coordinated development of social-ecological systems. However, most current studies focus exclusively either on the ecological or social effects of landscape fragmentation, lacking a comprehensive understanding of its overall impact on integrated social-ecological systems. To address this gap, we constructed social-ecological networks under different gradients of landscape fragmentation and quantified their structural properties in the Qinling Mountains. First, we used multi-source data to quantify four key ecosystem services (ESs), including net primary productivity (NPP), water yield (WY), soil conservation (SC), and habitat quality (HQ). Then, we applied principal component analysis (PCA) to map the spatial distribution and temporal dynamics of the Landscape Fragmentation Composite Index (LFCI) in the Qinling Mountains. Based on this, we constructed social-ecological networks across different LFCI gradients by integrating ESs, meteorological variables, vegetation, topography, soil, and socio-economic factors through network analysis. Finally, redundancy analysis (RDA) and hierarchical partitioning analysis (HPA) were used to explore how network attributes responded to ESs across fragmentation gradients. The results indicated that from 2001 to 2020, the ESs of the Qinling Mountains showed an obvious fluctuation, while the LFCI exhibited a fluctuating downward trend at a rate of 0.0019 a −1 . Among the ESs, only WY increased by about 27.88 mm as LFCI gradients rose, whereas NPP, SC, HQ, and total ecosystem services decreased by 8.00 gC·m −2 , 165.07 t·ha −1 , 0.30, and 0.32, respectively. The intensification of landscape fragmentation impaired the functionality of the social-ecological system in the Qinling Mountains, leading to reduced network connectivity (−0.13), transitivity (−0.19), and density (−0.18), as well as increased modularity (+0.08), vulnerability (+0.03), and path length (+0.25). These changes indicate a shift toward a looser, more fragmented, and less resilient network structure. Among all ESs, SC had the strongest influence on network attributes (R 2 > 0.6), while among network attributes, connectivity was most significantly affected. ESs explained 95 % of the changes in network attributes, highlighting SC and NPP as key elements in maintaining network stability. Overall, intensified landscape fragmentation weakened the provision of ESs and exacerbated the degradation of the social-ecological system in the Qinling Mountains. This study offers coordinated governance solutions and theoretical references for regions facing the dual challenges of human well-being and nature conservation.