Bushfire risk to life and property and ecological values

Forest Fire Management Victoria’s fuel management program – and all activities it undertakes to reduce bushfire risk – are designed to meet the bushfire management objectives outlined in the Code of Practice for Bushfire Management on Public Land 2012:

1. To minimise the impact of major bushfires on human life, communities, essential and community infrastructure, industries, the economy and the environment. Human life will be afforded priority over all other considerations.

2. To maintain or improve the resilience of natural ecosystems and their ability to deliver services such as biodiversity, water, carbon storage and forest products.

Bushfire risk

In Victoria, our landscape, climate and dispersed communities mean that we will always live with the risk of bushfires. Learning to live with this risk means we need to learn about what creates it, where it exists in our environment and what the government, communities and individuals can do to reduce the likelihood and impact of bushfires.

Bushfire risk refers to the likelihood of something being impacted by a bushfire. It includes the likelihood of a fire starting, growing and spreading across a landscape and the likelihood of things being in the path of the fire (such as houses, farms, roads, the natural environment and people).

Forest Fire Management Victoria (FFMVic) models the impact its fuel management program has on reducing bushfire risk. This impact is calculated and expressed as the percentage of bushfire risk ‘left over’ after fuel in forests has been reduced, either through fuel management activities or bushfire. The calculation of impact that FFMVic’s fuel management program contributes to managing bushfire risk only considers the contribution of planned burning at this point in time. New metrics are currently being developed that will enable FFMVic to assess and report on the contribution to bushfire risk reduction made by other prevention, preparedness and response activities, including mechanical fuel treatment.

FFMVic’s fuel management program aims to keep bushfire risk at or below 70% of Victoria’s potential maximum bushfire risk. “Maximum bushfire risk”, i.e. 100%  is calculated as the risk that would be present across the state using a model that assumes the worst conditions are released, including maximum fuel build-up and extreme bushfire conditions (Forest Fire Danger Index of 130).

Victoria’s bushfire risk at the end of 2019–20 has been estimated at 64%, down from 69% in the previous reporting period. Without intervention, the combined contribution made by FFMVic’s fuel management program and bushfires, Victoria’s bushfire risk level would have risen to 74%. As has been well documented, the 2019–20 bushfire season was one of the largest on record, with over 1.5 million hectares burnt. While over the long term, planned burning contributes to approximately two-thirds of the risk reduction achieved statewide, the massive extent of bushfires in 2019–20 meant that bushfire contributed the majority of risk reduction recorded during this year.

Despite a huge concentration of resources being dedicated to bushfire suppression and recovery over an extended period and weather conditions in spring 2019 and autumn 2020 not being favourable for planned burning, FFMVic still managed to treat 37,399 ha through burning and a further 17,635 ha through mechanical or other fuel treatment methods.

Relative contribution of planned burning and bushfires to risk reduction

For the first time, FFMVic has been able to model the relative contributions of planned burning and bushfires to reductions in bushfire risk. This modelling highlights how effective well-planned and delivered fuel management can be in reducing bushfire risk, especially when compared to the scale of bushfire required to achieve a similar reduction.

The results vary depending on the range of years selected. However, regardless of the years chosen, the analysis clearly shows that the majority of risk reduction has been achieved through planned burning, even when considering the influence of major bushfires (such as the 2009 Black Saturday fires and 2019–20 fires).

On average, from July 2009 to June 2020, planned burning accounted for two-thirds (66%) of the total risk reduction, compared to one-third (34%) for bushfires. This is despite bushfires burning an additional 900,000 hectares compared to planned burning planned burning. This is because we use the best-available science and data to target areas for planned burning (such as close to high-value assets) to maximise risk reduction, whereas bushfire burns locations randomly.

Even since July 2008, planned burning still accounts for over half (52%) of the risk reduction, compared to bushfires (48%). Importantly, during this period bushfires burnt over 1.2 million ha more than planned burning: 2.9 million ha burnt by bushfire, compared to 1.7 million ha by planned burning.

Unfortunately, an unwanted consequence of bushfires is that they often realise the risk we are trying to mitigate: that is, they result in losses of life and property and major environmental damage.

Our analysis has been independently examined by the University of Melbourne, which considers the analysis’ methodology to be valid. Its examination observed that while there will never be a perfect method for measuring risk, the methods used for the analysis can be justified, based on current research results.

The figure below shows the rolling ten-year average bushfire risk reduction attributable to planned burning and bushfires across Victoria since 2007. Each bar represents the average bushfire risk reduction attributable to planned burning compared to bushfires over ten-year periods.

The figure below shows Victoria's bushfire risk profile from 1980 to 2020 and its forecast risk through to 2023. It tells the story of how bushfire risk changes over time, based on bushfire history and our fuel management activities. We use this information to predict how risk will change because of our future planned burning and to compare the effectiveness of different bushfire management strategies.

The figure shows Victoria’s bushfire risk profile for the period 1980–2020 and projected changes in bushfire risk until 2023. It shows statewide bushfire risk:

• is 64% in 2019–20, down from a projected level of 74% (assuming the absence of bushfire and/or fuel management)
• is five percentage points lower than 69% reported at the end of 2018–19
• was largely influenced by the 2019-20 bushfire, however in a season with limited opportunities, FFMVic maximised its fuel management program, with a 50% increase in mechanical fuel treatments
• is projected to fall to 54% by 2023 if we implement the entire Joint Fuel Management Program but would increase to 70% without any fuel management activity (note: these figures exclude the unknown contribution of bushfires).

Reaccumulating fuel in Victoria’s forests can quickly increase bushfire risk if the fuel is not properly managed through regular fuel management activities.  FFMVic’s 3-year forward program for fuel management will involve an expansion of large-scale mosaic burning to complement the existing program of precision burning close to communities and assets.  The priority areas for risk reduction include the forested areas between Ballarat, Castlemaine, Macedon and Bacchus March, the Surf Coast and Otway hinterland as well as the forests to Melbourne’s north and east.  Large scale burns will be focussed on the forested landscapes of the Great Divide as well as reintroducing fire into the Grampians National Park and the central highlands.

The planned burn program will be supported by an enhanced mechanical treatment program, which will see works continue along the Surf Coast and Great Ocean Road, around the communities in the Wombat State Forest as well as the peri-urban interface to Melbourne’s east.

This will be done in conjunction with other non-fuel management bushfire management actions including working in partnership with other fire agencies, local government and communities to better understand local bushfire risk and what can be done, enhanced bushfire detection, tracking and response capability and capacity as well as continuing to support Traditional Owner led cultural fire practices.

Ecosystem resilience

Both objectives in the Code of Practice for Bushfire Management on Public Land 2012 have elements that relate to the protection and maintenance of environmental health. These objectives are:

• To minimise the impact of major bushfires on human life, communities, essential and community infrastructure, industries, the economy and the environment: human life will be afforded priority over all other considerations, and
• To maintain or improve the resilience of natural ecosystems and their ability to deliver services such as biodiversity, water, carbon storage and forest products.

FFMVic’s fuel management program considers how best to meet both objectives and recognises the need to manage these objectives over different temporal and geographic scales. This is achieved through managing fuels and conducting burns to protect, maintain and or improve ecosystem values and build ecosystem resilience. Fire is a natural and vital process for many of Victoria’s ecosystems, and ecosystem resilience reflects this natural relationship between fire, regeneration and ecosystem health.

To understand the effects of fire, both natural and fuel management on the environment, we measure and monitor the timing and number of fires in different types of vegetation using their tolerable fire intervals (TFIs). We also measure and monitor the ages of different types of vegetation using their growth stage structures (GSSs). We also partner with universities and institutes to undertake research to improve how we measure and represent ecosystem resilience.

We try to minimise the total area burnt while below minimum TFI because burning can be detrimental to ecosystem resilience. However, planned burning may be needed in some areas already below minimum TFI to reduce bushfire risk to life, property or priority ecosystems.

The figure below shows the area of public land in Victoria burnt by bushfires and planned burning while below minimum TFI since 1980. It shows that in 2019–20 about 760,00 ha, or about 10%, of vegetation on public land was burnt while below minimum TFI, an increase from 2018–19. The area of vegetation on public land burnt below TFI as a result of planned burns was less than 8,000 ha, which is below 1%.

The figures below show the area and the proportion, respectively, of each fire management zone treated by planned burning while below minimum TFI since 1980.

The first figure shows in 2019–20, the greatest area treated by planned burning while below minimum TFI were in the Bushfire Moderation Zones (BMZ), and Landscape Management Zones with smaller areas treated in Asset Protection Zones (APZ) and none treated in Planned Burn Exclusion Zones. The second figure highlights that the proportion of planned burning relative to a zone’s area was greatest in BMZ (30%) and APZ (19%). This is because APZ is relatively small in area and because we burn more frequently in APZ and BMZ to reduce bushfire risk to life and property.

We recognise that TFI is a coarse measure of ecosystem resilience that doesn’t recognise finer-scale vegetation responses to fire or the differing severity of planned burning and bushfires. However, it can help us with regional-scale decision-making. Our regional bushfire management strategies aim to minimise areas burnt while below minimum TFI where feasible, without failing to deliver on other regional objectives. There will also be instances (such as large fire footprints where fuels become flammable before ecological maturity is reached) where fire will need to be applied below minimum TFI to prevent larger areas or important habitat being burnt by more-intense bushfires.

It can take many years before the proportion of vegetation in older growth stages recovers to the proportion before major fire events such as the 1939 and 2009 Black Saturday fires: some vegetation communities can take up to 50 years or more to reach maturity.

We are continuing to improve our understanding of TFIs by monitoring the responses of different species of vegetation to fire and by investing in research that improves our ability to predict these responses. We are currently testing minimum TFI thresholds by collecting data about species that are sensitive to short inter-fire intervals (such as Banksia spinulosa var. cunninghamii).

We are also improving the TFI mapping by using species distribution models for key flora species on which minimum TFIs are based. This enables TFIs to be mapped more accurately.

Page last updated: 21/10/22