Interacting and compounding impacts: fire and forestry in the 2019–20 wildfires: Australia's Megafires: Biodiversity Impacts and Lessons from 2019-2020

The 2019–20 Australian wildfires had major impacts on forests (Collins et al. 2021), biodiversity (Ward et al. 2020), carbon emissions (van der Velde et al. 2021), human health and
property (Inspector General for Emergency Management 2020). The extreme temperatures
and prolonged drought, including climatic conditions associated with climate change, contributed to the extent and severity of the 2019–20 wildfires (van Oldenborgh et al. 2021;
Mackey et al. 2021b). Indeed, climate and fire weather are major contributors to fire behaviour (Jones et al. 2020). Key attributes of the 2019–20 wildfires, such as severity, were strongly
linked with fire weather (Collins et al. 2021; Lindenmayer et al. 2021). Beyond climate and
weather as key drivers of fire, other factors that can influence fire behaviour include slope,
aspect, fuel loads and fuel distribution (Catchpole 2002; Bradstock 2010; Sullivan et al. 2012).
In addition, past disturbance, such as past fires and logging, can influence the severity of fire
(Lindenmayer et al. 2020, 2021; Bowman et al. 2021; Taylor et al. 2021). Hence, how the forest
is treated before the fire can have impacts on the fire itself (Lindenmayer et al. 2021) (see Box
19.1). Here, we briefly examine some of the evidence for the compounding and interacting
effects of fire and logging, both in a pre-fire and post-fire (salvage) logging context. Many of
these insights come from work in Victoria. The bulk of empirical work from which we draw
examples has been conducted in the wet eucalypt forests of Victoria dominated by obligate
seeder tree species such as mountain ash (Eucalyptus regnans) and alpine ash (Eucalyptus
delegatensis), which are often killed by high-severity wildfires. However, some of the general
patterns we have outlined are also found in drier mixed species forests (Taylor et al. 2020)
and dry lowland forests (Lindenmayer et al. 2021; Taylor et al. 2021). We therefore suggest
that some of the general principles derived from these bodies of work apply in other forest
types, including those elsewhere in Australia and overseas.