Bushfires (wildfires) are uncontrolled fire in the landscape. These particularly affect natural or seminatural vegetation, and have significant positive and negative effects on landscape and ecosystem processes. Because Australia is a continent where bushfire is a common and, indeed, vital contributor to natural processes, and because many vegetation types encourage bushfires—with highly flammable foliage, litter and oils—bushfire can be beneficial to some species and ecological communities. For example, heat and smoke are required to stimulate germination in some species, high temperatures cause seed release in other species, and bushfires maintain habitat heterogeneity by leaving a mosaic of burnt and unburnt patches. On the other hand, bushfires that burn too hot, too frequently, or over too large an area may kill off regeneration, reduce landscape diversity, change soil characteristics, increase erosion and reduce water quality.
Australian weekly bushfire frequencies increased by 40 per cent during the period 2007–13 (Dutta et al. 2016), and some sites experienced fire more than 20 times between 1988 and 2015 (Russell-Smith 2016; Figure LAN4). Because weekly bushfire frequencies are strongly dependent on weekly trends in soil moisture, solar irradiation, fuel dryness and wind speed, these data indicate a major climatic shift. Such an increase in frequency is likely to be deleterious to some ecological communities, even those that are fire dependent (Murphy et al. 2010). There is increased recognition of the cost of uncontrolled bushfires, not just in human life and property, but also in ecosystem function and environmental services (Stephenson et al. 2013).
In response to increased understanding of the impacts of altered fire regimes, research and management actions are increasingly aimed at reintroducing more ‘natural’ fire regimes, analogous to historical Indigenous fire management practices or the patchiness of naturally occurring wildfires triggered by lightning strikes.