Functional connectivity in China’s coastal MPAs: modeling critical corridors and restoration zones for economic fish under climate change

Climate change is reshaping the distributions of marine species and disrupting functional connectivity among protected areas, yet few studies have quantified how these shifts alter the performance of marine protected area (MPA) networks. This study assessed climate-driven changes in functional connectivity for eight economically important fish species across 193 coastal MPAs in China under current conditions and two end-of-century scenarios (SSP1-2.6 and SSP5-8.5, 2090–2100). Ensemble species distribution models (mean AUC: 0.91–0.98; mean TSS: 0.75–0.93) were used to project h\abitat suitability, which was converted into resistance surfaces and analyzed via least-cost path and circuit-theory modelling to identify inter-MPA corridors, pinch-points, and barrier zones. Habitat responses diverged sharply between thermal guilds: warm-water species expanded in total area (B. taipingensis: +434.6% under SSP5-8.5), whereas cold-temperate species contracted severely (L. polyactis: −57.8%, with complete loss of high-suitability habitat). Functional connectivity exhibited asymmetric changes at the network level. Effective resistance declined 99% for A. japonica but increased 29-fold for S. niphonius under SSP5-8.5. Critically, corridor quantity and quality diverged for B. taipingensis, which gained 93% more corridors yet experienced a 47.8% increase in effective resistance—demonstrating that network expansion does not ensure improved connectivity. pinch-point counts increased across all four sea regions under SSP5-8.5 (most markedly in the Beibu Gulf: 16 to 28), and dual-stress zones where bottlenecks coincided with high-restoration-potential barriers concentrated along the Zhejiang–Fujian coast, the Bohai Strait, and the Pearl River Estuary. These results demonstrate that static MPA networks are progressively misaligned with dynamic species connectivity requirements, and identify spatially explicit priority zones where adaptive management intervention would yield compounding benefits for network-wide resilience.