Abstract <p>Freshwaters are among one of the most environmentally heterogeneous systems in the aquatic realm. However, the advance of human activities, such as pasture exploration, threatens the integrity and the biodiversity in these systems, putting pressure on their important ecosystem functions and services. In this study, we investigated the taxonomic and functional aspects of Odonata assemblages in streams located inside and outside a protected area, under the influence of pasture activities. We hypothesized that impacted streams would exhibit lower taxonomic diversity and environmental heterogeneity due to habitat degradation and that functional traits related to oviposition and territoriality would be reduced in such environments. Data was collected in 2023 using fixed area sweeping sampling in the Carajás National Forest, in Pará. We assessed taxonomic and functional diversity using Principal Component Analysis, Permutational Multivariate Analysis of Variance, Permutational Multivariate Analysis of Dispersion, Generalized Linear Models, and Dirichlet analysis to evaluate the influence of environmental variables. Our first hypothesis was partially supported, as taxonomic diversity differed between streams, although environmental heterogeneity did not. Differently, our second hypothesis was not supported, as the functional indices were associated only with limnological variables.</p> Implications for insect conservation <p>This study assessed Odonata diversity in streams inside and outside a national forest, associating species composition and functional indices to environmental variables. Taxonomic diversity was higher in protected streams, though environmental heterogeneity did not differ significantly. Functional diversity responded to limnological variables, with dissolved oxygen favoring species with unique traits and turbidity reducing functional richness and evenness, suggesting human impacts. Libellulidae and Coenagrionidae were associated with altered environments, while Polythoridae, Dicteriadidae, and Heteragrionidae indicated conserved sites. Despite limitations in sampling and trait coverage, results underscore the importance of riparian vegetation and water quality for sustaining aquatic biodiversity in Amazonian streams.</p>