Increasing agricultural land use in riparian networks negatively affects stream fish communities in a tropical savanna

Abstract

The Brazilian Cerrado has been experiencing intense land use changes for decades, with large-scale conversion of its natural vegetation to agriculture and livestock grazing. These agents of landscape change also affect the aquatic ecosystems embedded in the biome. Here, we investigated the effects of land use at different scales (catchment, riparian network, and local riparian) on fish assemblages in streams of the Brazilian Cerrado. We hypothesized that increasing agricultural land use (ALU%) reduces fish diversity and the compositional uniqueness of the fish assemblage. We used GLM to evaluate the impact of low-intensity ALU% on fish richness and abundance. Additionally, we employed beta regression to analyze the effect on local contribution to beta diversity (LCBD) and redundancy analysis to assess the impact on species composition. Our results showed that the effects of low-intensity ALU% depend on the spatial scale. While increasing ALU% in the riparian network negatively affected LCBD and altered species composition, ALU% in the catchment had negligible to slightly positive effects on LCDB, within the range of ALU% considered. Our findings reinforce the need to preserve riparian forests to maintain beta diversity in the streams of the Brazilian Cerrado. Also, no evidence was found that low-intense catchment use, without degrading the riparian forest, affects fish assemblages.