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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. [ABSTRACT FROM AUTHOR]

Aim: Many species are adapted to a particular fire regime and major deviations from that regime may lead to localized extinction. Here, we quantify immaturity risks to an obligate‐seeder forest tree using an objectively designed climate model ensemble and a probabilistic fire regime simulator to predict future fire regimes. Location: Alpine ash (Eucalyptus delegatensis) distribution, Victoria, south‐eastern Australia. Methods: We used a fire regime model (FROST) with six climate projections from a climate model ensemble across 3.7 million hectares of native forest and non‐native vegetation to examine immaturity risks to obligate‐seeder forests dominated by alpine ash (Eucalyptus delegatensis), which has a primary juvenile period of approximately 20 years. Our models incorporated current and future projected climate including fuel feedbacks to simulate fire regimes over 100 years. We then used Random Forest modelling to evaluate which spatial characteristics of the landscape were associated with high immaturity risks to alpine ash forest patches. Results: Significant shifts to the fire regime were predicted under all six future climate projections. Increases in both wildfire extent (total area burnt, area burnt at high intensity) and frequency were predicted with an average increase of up to 110 hectares burnt annually by short‐interval fires (i.e., within the expected minimum time to reproductive maturity). The immaturity risk posed by short‐interval fires to alpine ash forest patches was well explained by Random Forest models and varied with both location and environmental variables. Main conclusions: Alpine ash forests are predicted to be burned at greater intensities and shorter intervals under future fire regimes. About 67% of the current alpine ash distribution was predicted to be at some level of immaturity risk over the 100‐year modelling period, with the greatest risks to those patches located on the periphery of the current distribution, closer to roads or surrounded by a drier landscape at lower elevations. [ABSTRACT FROM AUTHOR]

Abstract 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. Highlights • Flammability of vegetation is often assumed to increase with time since fire. • We tested this assumption across a productivity gradient in five forest communities. • Increased flammability with time since fire was found in heathland and wet forests. • Contrary results were found in tall mixed, foothills and forby forests. • Benefits of fuel treatments will not be equal across all vegetation communities. [ABSTRACT FROM AUTHOR]

Traditional population viability analysis (PVA) does not address the degree of measurement error or spatial and temporal variability of vital rate parameters, potentially leading to inappropriate conservation decision-making. We provide a methodology of applying Bayesian network (BN) modeling to PVA addressing these considerations, particularly for species with complex stage-class structures. We provide examples of three species from eastern Australia - hip pocket frog (Assa darilingtoni) , squirrel glider (Petaurus norfolcensis) and giant burrowing frog (Heleioporus australiacus) , comparing traditional matrix-based PVA with BN model analyses of mean stage abundance, quasi-extinction probability, and interval threshold extinction risk. Both approaches project similar population sizes, but BN PVA gave more clearly identifiable thresholds of population changes and extinction levels. The PVA BN uniquely represents complex stage-class structures and in a single network, including variation and uncertainty propagation of vital rates, to better inform conservation management decisions. • Conservation decision-makers rely on results modeling viability of at-risk species. • Traditional modeling does not address uncertainty propagation and temporal changes. • A Bayesian network approach solves this for species with complex life histories. • Our approach more clearly identifies population thresholds and extinction levels. • It shows viability as probabilities for use in conservation risk management. [ABSTRACT FROM AUTHOR]

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. • Drivers of cost should be considered in wildfire management decisions. • Prescribed burning, mulching, fuel breaks, and suppression are economies of scale. • Other drivers of costs vary between management actions, regions, and environments. • Future decision tools should balance management costs with potential benefits. [ABSTRACT FROM AUTHOR]

Aim: The aims were: (1) to identify the environmental drivers of interannual variation in wildfire extent and severity; (2) to examine temporal trends in climatic potential for large and severe wildfires; and (3) to assess whether environmental conditions experienced during the 2019–2020 mega‐fire season were anomalous. Location: South‐eastern Australia. Time period: 1953–2020. Major taxa studied: Temperate forests. Methods: We used satellite‐derived fire severity mapping from 1988 to 2020 to model the effects of drought, weather and fuels on the annual area burned and the proportion of the area burned that was impacted by high‐severity fire across four bioregions. Trends in wildfire extent and severity were then estimated from 1953 to 2020 using these derived models and gridded climate data to assess changes in climatic potential for large and severe wildfires. Estimates of wildfire extent and severity for the 2019–2020 fire season were then assessed against prior seasons (1953–2019). Results: Annual area burned was positively related to the severity of seasonal drought and frequency of fire weather conditions that promote substantial daily fire growth. Wildfire severity was elevated in years with severe fire weather and increased with increasing antecedent drought in years without severe fire weather. Fuels had a lesser effect on wildfire extent and severity than climate. Potential fire extent and severity have increased over time in response to an increased severity of drought and worsening fire weather conditions. Estimates of wildfire extent and severity during the 2019–2020 fire season approached the upper extreme within each bioregion, owing to widespread extreme climatic conditions. Main conclusions: The climatic potential for large and severe forest fires has increased across south‐eastern Australia since the 1950s, probably because of anthropogenic climate change. The magnitude and severity of the 2019–2020 fires reflected climatic conditions that are driving an increase in the size and severity of wildfires. [ABSTRACT FROM AUTHOR]