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 better understand what creates bushfire risk, 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 we value 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 of its fuel management program on reducing bushfire risk. We calculate this impact and express it as the percentage of bushfire risk ‘left over’ after fuel in forests has been reduced, either through planned burning or bushfire. At present, we are unable to include the risk reduction contribution of mechanical fuel treatment. FFMVic is currently developing new metrics that will enable us to assess and report on the contribution to bushfire risk reduction made by other prevention, preparedness, and response activities, including mechanical fuel treatment, for inclusion in future risk calculations and reporting.

FFMVic’s fuel management program aims to keep bushfire risk at or below 70 per cent of Victoria’s potential maximum bushfire risk. ‘Maximum bushfire risk’ is calculated as the risk that would be present across the state using a model that assumes the worst conditions are realised, including maximum fuel build-up and extreme bushfire conditions (Forest Fire Danger Index of 130). We refer to this as 100 per cent residual risk.

Victoria’s bushfire risk at the end of 2020–21 has been estimated at 63 per cent, down from 64 per cent in the 2019–20 reporting period. Without the risk reduction resulting from FFMVic’s planned burning program and from bushfires, Victoria’s bushfire risk would have risen to 67 per cent.

Relative contribution of planned burning and bushfires to risk reduction

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

The results vary depending on the range of years selected. However, regardless of the years selected, the analysis clearly shows that most 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 2021, planned burning accounted for more than two-thirds (69 per cent) of the total risk reduction, compared to 31 per cent for bushfires - despite bushfires burning 800,000 hectares more than planned burning. This is because we use the best-available science and data to target areas for planned burning (such as areas close to high-value assets) to maximise risk reduction outcomes, whereas bushfire burns locations randomly.

The figure below shows the rolling ten-year average of 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 2021 and its forecast risk to 2024. 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 our future planned burning will change risk and to compare the effectiveness of different bushfire management strategies.

The figure shows Victoria’s bushfire risk has decreased from last year. The decrease is due to fuel reduction from the combination of planned burning and the bushfire season offsetting the regrowth in fuels since last year. Due to minimal bushfire activity in 2020–21, the majority of risk reduction during this period was attributable to planned burning.

The figure shows Victoria’s bushfire risk profile for 1980–2021 and projected changes in bushfire risk until 2024.

It shows that statewide bushfire risk:

• was 63 per cent in 2020–21, down from a projected level of 67 per cent (if there were no major bushfires or fuel management)
• was 1 percentage point lower than the 64 per cent reported at the end of 2019–20
• decreased in 2020–21, primarily because of planned burns offsetting the regrowth in fuels over the year, with FFMVic maximising its fuel management program under favourable weather conditions during spring 2020 and autumn 2021.

Re-accumulating fuel in Victoria’s forests can quickly increase bushfire risk if the fuel is not properly managed through regular fuel management activities. As the figure above shows, if we implement our Joint Fuel Management Program (JFMP) in full and there is little bushfire activity, modelling indicates bushfire risk will be 55 per cent by 2024. If we cannot implement the program and there is little bushfire activity, modelling indicates that bushfire risk is likely to rise to 71 per cent over the next three years.

We will support the planned burning program with an enhanced mechanical treatment program, including treating areas in high-risk locations that are historically complex or difficult to treat.

Ecosystem resilience

Both objectives in the Code of Practice for Bushfire Management on Public Land 2012 have elements related to the protection and maintenance of environmental health. The two 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.
• 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. We achieve this by 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 planned burning, 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). Also, we 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 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 2020–21, just over 25,800 hectares (less than 1 per cent) of vegetation on public land was burnt while below minimum TFI, a decrease from 2019–20. Of this, the area of vegetation on public land burnt below TFI through planned burns was less than 23,000 hectares.

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.

In 2020–21, Bushfire Moderation Zones and Landscape Management Zones had the largest extent treated by planned burning while below minimum TFI. We treated smaller areas below TFI in Asset Protection Zones and treated a very small area (2 hectares) below TFI in Planned Burn Exclusion Zones. Figure 6 highlights that the proportion of planned burning relative to a zone’s area was greatest in Asset Protection Zones (2.19 per cent), followed by Bushfire Moderation Zones (0.87 per cent), Landscape Management Zones (0.17 per cent) and Planned Burn Exclusion Zones (0 per cent).

We recognise that TFI is a coarse measure of ecosystem resilience that does not 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 priority regional objectives. There will also be instances (such as large fire footprints where fuels become flammable before ecological maturity is reached) where we need to apply fire below minimum TFI to prevent larger areas or important habitat from being burnt by more intense bushfires.

It can take many years before the proportion of vegetation in older growth stages recovers to the levels it was before major fire events (such as the 1939 Black Friday and 2009 Black Saturday fires). Some vegetation communities can take more than 50 years to reach maturity.

We continue 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 also improving TFI mapping by using species distribution models for key flora species on which minimum TFIs are based, so we can map TFIs more accurately.

Page last updated: 23/12/21