Direct and Indirect Effects of Natural and Anthropogenic Drivers on Avian Diversity in the Sanjiang Plain, Northeast China

Understanding how natural and anthropogenic factors jointly influence avian diversity is essential for biodiversity conservation and the sustainable management of large-scale wetland ecosystems, yet their combined effects remain insufficiently understood. This gap is particularly evident for land birds, as most studies focus on waterbirds. Using structural equation modeling, we quantified the effects of these drivers on habitat quality and avian richness in the Sanjiang Plain, separately for waterbirds and land birds. Our results show that: (1) habitat quality is primarily controlled by natural factors, particularly soil organic carbon (SOC), normalized difference vegetation index (NDVI), and topography, whereas human activities exert weak negative effects; (2) waterbirds are primarily associated with SOC- and temperature-driven pathways, whereas land birds respond more directly to climate and human disturbance; (3) natural drivers exert stronger effects than anthropogenic factors on both waterbird and land bird diversity; and (4) the effects of natural drivers differ between bird groups, with SOC and NDVI showing stronger effects on waterbirds, and precipitation and temperature being more influential for land birds. These findings highlight the need for group-specific conservation strategies, including conserving soil carbon and maintaining hydrological conditions for waterbirds, and enhancing vegetation and mitigating human disturbance for land birds.