Pyrogeographic analysis of drivers of lightning-ignited wildfires in Tasmania

Background: Recent studies have reported increasing frequency of lightning fires and associated burned area in Tasmania. Aims: To identify factors driving the frequency and scale of lightning-induced fires in Tasmania. Method: We compiled datasets on lightning activity, lightning fire, vegetation and fuel moisture. Multi-model inference was used to evaluate predictors of lightning fire. We determined the number of days annually with fuel dry enough to be susceptible to lightning fires. We examined temporal trends in lightning, lightning fires and fuel moisture between 2005 and 2022. Key results: Drier fuels and higher lightning density increased the probability of lightning fires, with areas of treeless vegetation being more susceptible than forests. Lightning fire-prone areas were concentrated in western and central Tasmania. However, no significant trends were found in lightning days or lightning fire days. There was a drying trend in fuel moisture in western and southern Tasmania, and a increasing wetness trend in northern and eastern regions. Conclusions and implications: Lightning fires are most likely in treeless vegetation with dry fuels and those exposed to intense lightning activity. The short record limits detecting temporal trends. High-resolution data on fuel dryness, lightning and ignitions are crucial for understanding lightning fire dynamics.