Australia's temperate highland peat swamps face a death by a thousand longwall cuts

Australia's temperate highland peat swamps are headwater systems where sediment and organic matter have accumulated over millennia, with some swamps in Sydney's drinking water catchment dating back more than 15 thousand years. These environments provide a range of ecosystem services, including water regulation, carbon storage, drinking water supply, and habitat for specialised and refuge-dependent species. However, swamps face various threats that may impair delivery of ecosystem services, including longwall coal mining, extractive water use, bushfires, and climate change. Longwall mining causes severe impacts on peat swamps, resulting in the diminution or complete loss of ecosystem services. Persistent impacts from longwall mining on peat swamps in the southern coalfields of NSW will result in ecosystem collapse and loss of ecosystem services for many human generations into the future. This study assessed two scenarios: 'Protection', involving the cessation of new mining-induced subsidence impacts on upland swamps, and 'Status Quo,' where mining continues within existing leases. The consequences of these scenarios for upland swamps and their downstream catchments were assessed for a period approximately 50 years from 2025, representing the approximate duration over which mining would proceed under the Status Quo scenario. Results indicate that approximately 10 % of mapped upland swamps on the Woronora Plateau are already likely impaired by undermining and more than 45 % are at risk of accelerated collapse (rapid loss of swamp hydrological function and vegetation communities) if the status quo is maintained. Under the status quo scenario, numerous ecosystem services would be at further risk of decline, including carbon storage, fire resilience, provision of endangered habitat, and water purifying services, with projected losses quantified in the results. This study highlights a crossroads moment for peat swamp management and two alternative futures that pivot based on present-day management decisions. Prompt action to prevent further subsidence impacts is essential to avoid irreversible losses of ecosystem function, endangered species, and drinking water supply.