Supporting document 3: Identifying thresholds for responses of amphibians to groundwater and rainfall decline. A risk assessment and decision making framework for managing groundwater dependent ecosystems with declining water levels.
This project developed a methodology for predicting how nine amphibian species with different life histories could potentially respond to declining groundwater and declining rainfall – impacts which are occurring on the Gnangara Mound (north of Perth in south-western Australia). Bayesian Belief Networks (BBNs) were developed to describe the responses of three reproductive guilds: amphibians that breed in water, amphibians that breed in terrestrial nests that are later flooded, and one entirely terrestrial-breeding species. The BBN models showed that aquatic breeding species were most sensitive to changes in the hydroperiods, but were unable to demonstrate an impact of groundwater level as there was a lack of information needed to derive an empirical link between groundwater and hydroperiods. The terrestrial-aquatic breeding species were also sensitive to hydroperiod length, with declines in autumn and winter rainfall further decreasing the probabilities of population persistence. The BBN models also demonstrated the key role that seasonal rainfall events play in triggering reproduction, and suggest that the drier climates projected for south-western Australia will place additional stress on amphibian communities. While the BBNs developed here were largely conceptual, and thus preliminary, they demonstrate a promising approach for anticipating the impacts of groundwater decline on amphibians. Amphibians are key indicators of wetland health and under conditions of hydrological change it is important to be able to predict changes in their diversity and abundance.
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