River birds' response to hydrological extremes: New vulnerability index and conservation implications

There is growing evidence that as a consequence of climate change the frequency of extreme hydrological events will increase. Predicting the impacts of these extreme events on ecological systems is a major research challenge. It is predicted that change in future river flows, characterised by greater occurrence of floods and droughts, will have profound impacts on aquatic invertebrate communities by removing sensitive species and restructuring food networks. However, it remains unclear how an increase in these hydrological extremes will impact on riparian communities and species at higher trophic levels. Here, we describe a new methodology that facilitates the integration of quantitative outputs of species' distribution models with the expert knowledge of conservation practitioners to produce a species' vulnerability index (SVI). Using our SVI framework, we assessed and ranked the vulnerability of 16 river bird species to a potential climate-induced shift in the frequency, duration and magnitude of flood and drought events. Vulnerability was associated primarily with ecological traits that restrict species to in-channel riverine habitat. Whilst the SVI was developed to assess species' vulnerability to hydrological extremes on rivers, it is equally applicable to other environmental domains as well as a range of avian and non-avian taxa. Furthermore, this original methodological approach provides researchers and managers with a valuable conservation tool that allows them to identify the species most vulnerable to climate change impacts and plan mitigation and adaptation strategies.