Baetid abundances are a rapid indicator of thermal stress and riparian zone intactness

Riparian zone vegetation plays an integral role in freshwater ecology, notably by buffering water temperatures, and in providing habitat for the adult stages of many aquatic species. We measured the contribution that riparian vegetation makes to temperature buffering, and how this affects the freshwater fauna, specifically using changes in abundances of baetid may flies for the Luvuvhu River catchment in South Africa. Water temperatures were compared for shaded versus un-shaded sites, and thermal stress between seasons was estimated using a cumulative probability model for the most widespread mayfly species, Dabulamanzia media. It is concluded that thermal stress due to losses in riparian shading could be detected using mayfly abundances in a regular monitoring programme. •Losses in riparian shading are reflected in changes in water temperature signatures.•A simple model linked periods of thermal stress to reduced abundances in mayflies.•Mayfly abundances reflect the impacts of habitat change and indicate thermal stress.•Thermal stress can be mediated through maintaining naturally shaded riparian zones.