Costs of preventing and supressing wildfires in Victoria, Australia.

Land managers around the world are increasingly under pressure to demonstrate that the actions being used to moderate wildfire risk are effective and cost-efficient. However, little research to date has focused on determining cost-efficiency of management actions or identified the factors which increase the costs of performing such actions. Here, we aimed to identify the key drivers of cost for fuel management (prescribed burning, mulching, and slashing), fuel breaks, and suppression using data from the state of Victoria, Australia. We utilise generalised additive models to understand how environmental factors, terrain, location, and management decisions influence the cost of implementing wildfire management efforts. These models show that cost per unit declines as the area treated or the area of the fire increases for all four management approaches. Therefore, preventative, and responsive management actions represent economies of scale that reduce in cost with larger treatments. We also found that there were regional differences in the cost of fuel management and fuel breaks, potentially related to the structure of resourcing treatments in each region and the availability of land on which it is feasible to implement management. Cost of suppression per fire increased with the number of fire fighters and when there were more fires occurring concurrently in the landscape. Identifying the key drivers of cost for preventative and responsive management actions could enable managers to allocate resources to these actions more efficiently in future. Understanding drivers of cost-efficiency could be critical for adapting management to shifts in wildfire risk, particularly given climate change will alter the window in which it is safe to apply some preventative fuel management actions and reduce suppression effectiveness.

The fuel-climate-fire conundrum: How will fire regimes change in temperate eucalypt forests under climate change?

Fire regimes are changing across the globe in response to complex interactions between climate, fuel, and fire across space and time. Despite these complex interactions, research into predicting fire regime change is often unidimensional, typically focusing on direct relationships between fire activity and climate, increasing the chances of erroneous fire predictions that have ignored feedbacks with, for example, fuel loads and availability. Here, we quantify the direct and indirect role of climate on fire regime change in eucalypt dominated landscapes using a novel simulation approach that uses a landscape fire modelling framework to simulate fire regimes over decades to centuries. We estimated the relative roles of climate-mediated changes as both direct effects on fire weather and indirect effects on fuel load and structure in a full factorial simulation experiment (present and future weather, present and future fuel) that included six climate ensemble members. We applied this simulation framework to predict changes in fire regimes across six temperate forested landscapes in south-eastern Australia that encompass a broad continuum from climate-limited to fuel-limited. Climate-mediated change in weather and fuel was predicted to intensify fire regimes in all six landscapes by increasing wildfire extent and intensity and decreasing fire interval, potentially led by an earlier start to the fire season. Future weather was the dominant factor influencing changes in all the tested fire regime attributes: area burnt, area burnt at high intensity, fire interval, high-intensity fire interval, and season midpoint. However, effects of future fuel acted synergistically or antagonistically with future weather depending on the landscape and the fire regime attribute. Our results suggest that fire regimes are likely to shift across temperate ecosystems in south-eastern Australia in coming decades, particularly in climate-limited systems where there is the potential for a greater availability of fuels to burn through increased aridity.

Pathways of change: Predicting the effects of fire on flammability.

Impacts of wildfire on humans are increasing as urban populations continue to expand into fire prone landscapes. Effective fire risk management can only be achieved if we understand and quantify how ecosystems change in response to fire and how these changes affect flammability. However, there have been limited studies to this effect with the dominant paradigm being the assumption that recently burnt vegetation is less flammable than older vegetation. To better quantify changes in flammability, we first need to quantify trajectories of changes in response to fire within individual vegetation communities. Second, we need to examine the extent to which these changes alter flammability. Here, we quantify the flammability pathways with increasing time since fire for five vegetation communities in south-eastern Australia. A total of 116 sites were measured across a range of heathland, woodland and forest ecosystems. Flammability was measured using an ecological point based mechanistic fire behaviour model that estimates three measures of flammability relevant to both fire management and research. Predicted changes in flammability varied between vegetation types with heathland and wet forests generally increasing in flammability with time since fire and tall mixed, foothills and forby forests decreasing or showing limited changes with time since fire. Variations in flammability pathways suggest fire management activities that alter fuel structure, such as prescribed burning, may only reduce flammability in a limited set of ecosystems. Incorporating these results into a landscape analysis will improve the quantification of fire risk.