Habitat complexity mediates the impacts of human land-use on stream biodiversity

Abstract

Urban and cropland intensifications are persistent drivers of declines in biodiversity globally. Yet, it is poorly understood how habitat complexity can mitigate the negative impacts of such human pressures. Using a comprehensive dataset of 4093 streams across the conterminous USA, we demonstrate that high-habitat complexity sites harbor higher insect richness and density, but lower fish richness and density, than low-habitat complexity sites. Higher habitat complexity sites support 17% and 18% more fish and insect uniqueness, respectively. Urban and cropland intensifications lead to reductions in fish and insect richness and density in more complex habitats. Regardless of habitat complexity, urban and cropland intensifications have reduced insect uniqueness. These findings illustrate that despite promoting greater insect diversity and greater fish and insect uniqueness, high-habitat complexity cannot effectively buffer biodiversity against human land-use intensification. Our findings underscore that preserving freshwater biodiversity requires maintaining habitat complexity and more sustainable urban and agricultural activities.