In Victoria, there will always be a level of risk for bushfire. We talk about current levels of risk as being the percentage of risk ‘left over’ after fuel loads in the forest have been reduced – either through fuel management or bushfire.
Our fuel management program is driven by a statewide target to maintain bushfire risk at, or below, 70% of Victoria’s maximum bushfire risk. This means that bushfire fuels have been reduced to the point where impacts to life and property are reduced by about a third of the maximum risk.
The map below shows the 2017-18 bushfire risk for each of Victoria’s seven bushfire risk landscapes (BRLs).
Victoria's bushfire risk profile (1980 – 2018) tells a 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 risk management strategies. Victoria’s fuel management program on public land is driven by a statewide target to maintain bushfire risk at, or below, 70% of Victoria’s maximum bushfire risk.
Victoria’s bushfire risk increased slightly from last year because unfavourable weather conditions reduced planned burning opportunities.
Despite the limited opportunities to do planned burning due to poor weather conditions, our risk modelling technology and planned burning optimisation tool helped us determine places where planned burning would be effectively at reduce risk and target those priority areas.
BRLs are geographical areas of Victoria in which bushfires tend to behave in a similar way. We call them ‘risk landscapes’.
There are seven of them across Victoria, and our strategic planning for fuel management is currently based on these areas.
Importantly, risk is different across these different areas – as will be the strategies that we develop with communities to treat that risk.
Currently, risk is calculated and managed using BRL boundaries while operational activities and management is guided by regional boundaries. This means we work closely across overlapping boundaries to ensure the best risk reduction outcomes for communities and for maintaining a healthy environment.
Victoria's bushfire risk
Victoria's bushfire risk profile, 1980–2021
Victoria’s risk profile for the period 1980-2018 and projected changes in bushfire risk until 2021 shows that bushfire risk:
- was 66% statewide for 2017-18
- fell after the 1983 Ash Wednesday bushfires, which caused large losses of life and property
- rose steadily after 1983 as fuel re-accumulated across the state, reaching a peak of 81% in 2002.
- fell significantly as major bushfires in the 2000s, particularly the 2009 Black Saturday bushfires, reduced fuel: this reduced risk came at a cost of large losses of life and property
- has increased in recent years as fuel has re-accumulated.
Re-accumulating fuel in Victoria’s forests can quickly increase bushfire risk, if the fuel is not regularly managed. If we implement our Joint Fuel Management Program (JFMP) and there is little bushfire activity, modelling indicates that bushfire risk will be maintained at 60% by 2021. If we cannot carry out our planned fuel management activities and there is little bushfire activity, modelling indicates that bushfire risk is likely to rise steeply to 78% over the next three years.
Valuing our environment
We manage fuel and conduct ecological burns to maintain or improve ecosystem resilience. Ecosystem resilience is the environments ability to bounce back after fire.
To understand the effect of fuel management on ecosystem resilience, we measure and monitor the tolerable fire interval (TFI) and growth stage structure (GSS) of the vegetation in areas we treat through our bushfire fuel management program. We also partner with universities and institutes to undertake research to improve how we measure and represent ecosystem resilience. This research includes how to best use the metric geometric mean abundance to represent ecosystem resilience. In 2017-18, we continued testing and refining our method for calculating geometric mean abundance, which will be adopted statewide in the future.
Tolerable fire interval across Victoria
The figure below shows the tolerable fire interval (TFI) status since 2007 of the vegetation on public land across Victoria. It shows about 50% of the vegetation was below its minimum TFI in 2017-18, as it has been for a decade. This trend is mainly a legacy of the 2003, 2006–07 and 2009 bushfires. The amount of vegetation below minimum TFI will remain consistent for a long time because many bushfire-affected vegetation types have relatively long TFIs: between 15 and 80 years. Despite an increase in the amount of planned burning since 2009, the trend of vegetation within TFI has increased in 2017-2018 to 25%. Substantial areas of fire-affected vegetation in the Alpine North East and Alpine Greater Gippsland have reached reproductive maturity and have shifted into the within TFI categories, influencing the statewide TFI trends. This is a result of our strategic planning to reduce the effects of the planned burning program on TFI and on ecosystem resilience more broadly.
TFI status of public land vegetation, Victoria, 2007–18
The figure below shows the area of public land burnt by bushfires or planned burning while below minimum TFI in the period 2007–18. We try to minimise the amount of area that is burnt while below minimum TFI because it 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. We continued to see a multi-year decline in the overall area burnt by bushfire or planned burning while below minimum TFI. In 2017-18, less than 1% of the vegetation in Victoria was burnt while below TFI. The total area burnt while below minimum TFI in 2017–18 was lower than the previous year. Despite increases in the area burnt by bushfires while below minimum TFI, most of this reduction is the result of carefully targeted planned burning.
Area of public land burnt while below minimum TFI, Victoria, 2007–18
The figure below shows the area of each fire management zone treated by planned burning while below minimum TFI between 2007–18. The next figure shows the proportion of each zone treated by planned burning while below minimum TFI over the same period.
The figure below shows the greatest areas treated while below minimum TFI are in Landscape Management Zone (LMZ) and Bushfire Management Zone (BMZ), with smaller areas treated in Asset Protection Zones (APZs). However, the next figure shows that the proportion of area treated by planned burning while below minimum TFI is greatest in APZ. This is because APZ is relatively small in area and because we burn more frequently in APZ to protect life and property. The proportion of landscape burnt while below minimum TFI in LMZ and BMZ is low compared with APZ. Overall, the proportion of fire management zones treated by planned burning while below minimum TFI was very low in 2017-18 (<5%). This shows our strategic bushfire management planning is resulting in carefully considered planned burning to reduce impacts on vegetation below minimum TFI.
The code of practice requires us to manage bushfire risk to protect people and property as well as to maintain or improve environmental values. It is important that we find the right balance between reducing fuel in the various fire management zones and minimising planned burning impacts on environmental values: doing so is part of the strategic planning process.
Area treated by planned burning while below minimum TFI, by fire management zone, 2007–18
We will continue to improve our understanding of TFI 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 mapping of TFI through the use of species distribution models for key flora species that define minimum TFI. This enables TFI to be mapped more accurately.
Proportion of each fire management zone treated by planned burning while below minimum TFI, 2007–18
Growth stage structure across Victoria
This figure below shows changes in statewide vegetation growth stage structure (GSS) in the period 2007–18. It shows that as vegetation on public land across Victoria has aged, some vegetation has moved from the juvenile growth stage (down by 2% since 2017) to the adolescent growth stage, however the most substantial shift has been from the adolescent growth stage (down by 6% since 2017) to the mature growth stage (up by 8% since 2017).
A relatively high proportion (about 23%) of public land has no recorded fire history. Nothing can be inferred about the TFI and GSS of public land with no recorded fire history.
GSS status of vegetation on public land, Victoria, 2007–18
Page last updated: 21/12/18