Deforestation impacts on environmental conditions of headwater streams and Ephemeroptera (Insecta) diversity in Southwestern Amazonia

The Amazon, home to the planet’s greatest biodiversity, faces increasingly intense and frequent degradation due to land-use changes and land conversion. These actions, although dominant in terrestrial systems, have a severe impact on aquatic ecosystems, which are closely dependent on surrounding landscapes, particularly riparian vegetation. Given this scenario, this study evaluated the influence of forest loss on environmental conditions and Ephemeroptera (Insecta) diversity in 21 streams of the Guaporé River basin, Rondônia, Brazil. Using 1-km buffer zones around watersheds, we classified the forest cover gradient based on existing forest percentages and analyzed habitat structure, water physicochemical parameters, and stream dimensions (width, canopy cover, and depth). Results showed that forest loss significantly increased stream depth and had a negative impact on canopy cover. Contrary to our initial hypothesis, genus richness was positively correlated with forest loss, with 33% of the variance in genus richness explained by the quadratic regression model, indicating a non-linear relationship. However, abundance was unaffected by land-use gradients. Distance-based redundancy analysis (db-RDA) revealed that 55% of the variation in Ephemeroptera genus distribution was explained by restrictive environmental variables (e.g., turbidity, water temperature, depth, discharge, and canopy cover), highlighting their role in community structuring. These findings demonstrate that forest degradation alters habitat structure and the composition of Ephemeroptera communities, with potential consequences for the health of aquatic ecosystems. Forest restoration in altered areas and conservation in less impacted ones is urgently needed to ensure water quality and biodiversity preservation.