Devastating bushfires ravaged south eastern Australia during the 2019/20 summer with over 11 million hectares burnt including 13.6% of total platypus habitat in Australia. The affected area was previously considered a stronghold for the iconic platypus – a species under ongoing threats in other parts of it’s range from drought, altered flow regimes, and habitat destruction. However, little empirical data exists on the impacts of bushfires on platypuses with previous studies hampered by a lack of rigorous pre-fire data.
This project used environmental DNA (eDNA) sampling to quantify the impacts of the bushfires on platypuses at a landscape level for the first time using a rigorous before-after-control-impact (BACI) design and generalised linear mixed models (GLMM). Water samples for eDNA analysis were collected from 142 sites throughout southeastern Australia before and after the fires.
Site occupancy was high in both treatment groups before the fires, highlighting the health of platypus populations in the area. Prior to the bushfires, platypuses were detected at 40 of the 48 sites (83%) within the fire extent. After the fires, this decreased to 33 out of the 48 sites (69%), a decline of 14%. In comparison, of the 94 control sites, platypuses were detected at 68 sites prior to the bushfires (70%), and 70 after (75%). The estimated decline was slightly higher (18%) when data was restricted to native vegetation classes only. The GLMM estimated a significant negative impact of bushfires on platypus presence when the dataset was restricted to native vegetation classes.