Combined effects of climate and anthropogenic change on habitat suitability and distribution of threatened marine species in China’s coastal waters

Understanding how climate change and anthropogenic stressors jointly affect threatened marine species is critical for conservation planning, yet integrated assessments remain scarce in China’s coastal waters. Using an ensemble species distribution modelling framework (Biomod2) with six algorithms, we projected habitat suitability for ten threatened marine species under climate-only and global-change scenarios for 2040–2050 under SSP1-2.6 and SSP5-8.5. Predictors included 13 natural variables and four anthropogenic variables (fishing pressure, coastal pollution, aquaculture intensity, and shipping density). Ensemble models achieved high predictive performance under both predictor sets (climate-only: mean TSS = 0.87, AUC = 0.96; global-change: TSS = 0.80, AUC = 0.92), consistently outperforming individual algorithms. Mean sea temperature, dissolved oxygen, and bathymetry were the dominant natural drivers, while fishing pressure (up to 16.2%) and coastal pollution (up to 29.5%) were the most influential anthropogenic factors. Under climate-only scenarios, species distribution centroids shifted northward at mean rates of 22.12 km·decade-1 (SSP1-2.6) and 47.91 km·decade-1 (SSP5-8.5), with Tachypleus tridentatus (98.99 km·decade-1 under SSP5-8.5) and Hippocampus trimaculatus (83.64 km·decade-1) showing the greatest displacement. Habitat responses were highly species-specific: A. glauca, M. griseus, and H. trimaculatus exhibited net expansion, whereas C. mydas and P. largha experienced consistent contraction. Critically, incorporating anthropogenic stressors substantially reduced habitat availability across the assemblage, with mean suitable area per species declining from 31, 813 km² (climate-only) to 19, 080 km² (global-change), a 40.0% reduction. Anthropogenic pressures even reversed climate-driven gains for several species, most notably H. nehereus (from +87.2% to −16.3% under SSP5-8.5) and S. kobiensis (from +2.1% to −86.0%), and intensified contractions for C. mydas and P. largha. Cumulative habitat suitability mapping further identified the Pearl River Estuary, western Taiwan coast, Yangtze River Delta, and central Bohai Sea as priority regions where climate refugia overlap with intense human activities. These findings demonstrate that anthropogenic pressures can transform potential climate refugia into ecological traps, amplifying climate-driven habitat loss, and underscore the urgent need for integrated marine spatial planning addressing both climatic and anthropogenic threats in China’s coastal waters.