Climate outweighs anthropogenic impacts in shaping Yangtze planktonic and benthic biodiversity under protection initiative

Under major conservation policies like the Yangtze River Protection Initiative, understanding the shifting balance between climate drivers and anthropogenic activities as drivers of biodiversity is critical. Yet, their relative impacts following the Yangtze River Protection Initiative, a catchment-scale ecological conservation and green-development strategy first proposed in 2016, remain poorly quantified. Here, we investigated planktonic and benthic biodiversity patterns along the 2800 km Yangtze River following China’s largest river protection initiative. Comprehensive sampling of phytoplankton, zooplankton, and macrozoobenthos was conducted at 117 sites, revealing distinct longitudinal zonation patterns delineated by the Three Gorges Dam and the Datong tidal limit, with species turnover dominating community spatial heterogeneity. Our analyses identified climatic factors, specifically air temperature, precipitation, and potential evapotranspiration (PET) during the sampling period, as key predictors of aquatic biodiversity across all three taxonomic groups, collectively outweighing the measured anthropogenic indicators. Machine-learning and mediation analyses revealed that climatic factors were associated with biodiversity through both direct paths and indirect pathways mediated by water quality, whereas the measured anthropogenic effects were dominated by direct pathways. Notably, the Yangtze River Protection Initiative significantly improved water quality and mitigated anthropogenic pressures, thus amplifying the relative importance of climate factors. Our findings highlight the critical role of climate in shaping river ecosystems at macroscale under the protection initiative and offer valuable insights for adaptive management strategies aimed at conserving freshwater biodiversity and enhancing ecosystem resilience in large rivers facing global environmental change.