Environmental water requirements and climate sensitivity of Australia's upland swamps

In South-East Australia, headwater peatlands (or upland swamps) support ecological communities that are listed as endangered under environmental legislation. Upland swamps provide ecosystem services via water stored within their sediments, and the regulation of flows to downstream environments. However, the impacts of climate change on their hydrology remains poorly understood. In this study, we used an upland swamp water balance model calibrated to daily observed water storage volumes and discharges at three upland swamps. These models were forced with climate projection data to investigate the sensitivity of upland swamps to changing climates and assess their water requirements for ecosystem function and habitat provision. We also compared these results to a model calibrated to simulate groundwater losses associated with longwall mining. Our findings indicate that the ecosystem services provided by upland swamps, including carbon sequestration and flow regulation, are likely to diminish under future climates. Storage volumes in the high-emissions scenarios showed significantly longer periods below critical thresholds for peat formation and habitat availability compared to the low-emissions scenarios. In the undermined swamp model, water storage levels were below critical thresholds for over 90 % of the simulation period. Generalised environmental water requirements were achieved at consistently lower rates for the future climate scenarios, though the lowest rates of achievement were for the undermined swamp model. Given the limited extent of upland swamps and their endangered ecological community status, these results highlight the need for enhanced protective actions against key threatening processes, such as underground mining and water extraction.