Understanding the effects of changing climates on the processes which support aquatic biodiversity is of critical importance for managing aquatic ecosystems. Using manipulative experiments, we assessed the community-level responses of aquatic ecosystems to a realistic future temperature regime which included extreme events. There was evidence of major changes in community composition, with an unpredictable suite of species favoured. Body size of component species declined, and there was evidence that the top-down (grazing) influence of stream invertebrates was reduced, allowing increased algal biomass. Emerging aquatic insects were smaller, and timing of emergence was altered, with potential impacts for terrestrial consumers which rely on this resource. In some species, there were temporal mismatches between emergence of the sexes, with potential impacts on species’ persistence. Field studies were used to determine the potential for riparian plantings to reduce stream temperatures of sufficient magnitude to mitigate against these effects. There was evidence that riparian replanting was sufficient to cool stream reaches to a degree consistent with preventing the predicted increases under climate change scenarios. There is potential therefore to use revegetation activities to mitigate against the impacts of warming climates in aquatic processes and biodiversity.