Biodiversity and habitat complexity buffer the destabilizing effects of anthropogenic activities on riverine fish communities.

Riverine fish communities are essential for the functioning of aquatic ecosystems and provide important ecosystem services for fisheries. Yet, anthropogenic environmental changes pose threats to fish communities and result in population collapses and reduced yields, underscoring the need to understand their stability from local to regional scales. In this study, we leverage long-term observational data of riverine fish communities in 108 hydrological basins across the globe to determine how anthropogenic activity, biodiversity, and habitat complexity jointly influence riverine fish community stability (i.e., temporal invariability of total fish abundance) at the site and basin scales. Our analyses show that anthropogenic activities represented by human footprint index decrease fish community stability across spatial scales; however, biodiversity and habitat complexity buffer these destabilizing effects by providing insurance effects at both site and basin scales. Specifically, biodiversity has consistently stabilizing effects across scales through enhancing the asynchrony within and/or among fish communities. At the basin scale, greater habitat area increases gamma stability by enhancing spatial community asynchrony. Our findings underscore the importance of conserving both fish biodiversity and habitat complexity to sustain the stability of riverine fish communities in the Anthropocene.