The Australian bushfires of summer 2019-20 had drastic impacts on catchments and waterways that are yet to be fully understood. Seventy-one percent of the Greater Blue Mountains World Heritage Area (GBMA) was affected by these fires, contributing to the International Union for the Conservation of Nature downgrading the status of the area to of Significant Concern in 2020. To date, much of the research on the impact of fires has focussed on catchment hydrology and physical water quality. Less is understood about impacts on aquatic macroinvertebrates, and hence the ecological health of waterways post-fire.
This paper analyses long-term data from Blue Mountains City Council’s aquatic monitoring program, to assess the impact of the bushfires on headwater streams in the GBMA. We compare the macroinvertebrate community, waterway health ratings, and basic physical water quality parameters pre-fire and post fire, at sites with over twenty years’ of data. More detailed water quality sampling, including nutrients, total suspended solids, dissolved organic carbon, dissolved metals, cations and anions was carried out post-fire at a subset of burnt sites and unburnt control sites.
Results indicate that the aquatic ecosystems of these streams have a high level of resilience, but are susceptible to impacts from floods and urban stormwater. The need for management that builds the resilience of waterways with urban catchments is emphasised by these results. This contributes to a growing body of research on fire impacts, building capacity for adaptive management in the Blue Mountains area and beyond.