A functional-trophic pathway links riparian land use intensification to riverine community stability

Intensive land use is transforming river corridors worldwide, with the agricultural and urban land use intensification being most prominent. Understanding how these pervasive pressures affect functional and trophic community structure-and ultimately ecosystem stability-is thus critically needed. Here, we disentangle the contribution of agricultural and urban land use changes on aquatic ecosystems by combining high-resolution environmental DNA (eDNA) surveys across 213 spatially and temporally stratified sampling sites with functional trait profiling and metaweb-based trophic networks in a major subtropical river. We found that the functional trait composition of fish, aquatic insect and algae was strongly structured and exhibited pronounced temporal reorganization. Riparian land use intensification was consistently associated with lower functional diversity and structural complexity of metaweb-derived local trophic networks, including lower modularity, nestedness and robustness, along agricultural and urban impervious land use gradients. Functional diversity and trophic network structure were strong positive predictors of community stability, and piecewise structural equation models indicated that increasing land use intensity destabilizes multitrophic communities primarily by suppressing functional and structural attributes, rather than through direct pathways. Overall, by uniting these two pathways within a single empirical framework, our study provides a mechanistic basis for predicting how human land conversion undermines ecosystem stability and offers a foundation for safeguarding biodiversity in rapidly changing environments.