Why hazard reduction burning is no smokescreen

By Ruth DawkinsOctober 5th, 2021

Used alongside other fire management approaches, hazard reduction burning can reduce the impact of bushfire on property and loss of life.
A raging Australian bushfire with large flames against a green forest. Image/Flickr

Extreme events such as bushfires are becoming more common in Australia. Image/Flickr

The how and why of hazard reduction burning

Australia’s unique climate and geography have always left us vulnerable to extreme weather events, but climate change is now exacerbating those conditions further.

We are experiencing bushfires that are more severe and more frequent, putting unprecedented stress on communities and response teams, and resulting in substantial social, environmental and economic costs.

In such challenging circumstances, we need to use a toolbox of approaches for risk reduction. One of those tools is hazard reduction burning, a technique that has an important role to play in fire management across Australia.

What is hazard reduction burning?

When bushfires occur, their behaviour is driven by three factors: weather conditions, terrain, and fuel. Of these three, the factor that we can have the most direct influence on is fuel – fine combustible vegetation and debris like dry grass, dead leaves, bark, and twigs.

Hazard reduction burning is the deliberate, controlled use of fire in the landscape undertaken during low-risk conditions to reduce the availability of the fuel that feeds a bushfire.  Hazard reduction burning is just one type of prescribed burning, which may be undertaken for various purposes. These purposes include removal of post-harvest forestry debris, site preparation and seedling regeneration, cultural reasons, ecological management or biodiversity habitat management. Each of these will also have some impact on reducing bushfire hazard, even though that is not their primary purpose.

Low-risk conditions typically occur in early spring and late autumn in southern Australia, when the fuel is dry enough to burn but we are not subject to the high temperatures, low fuel moistures and strong winds that would risk the fire getting out of control.

Used alongside other fire management approaches, hazard reduction burning can reduce the intensity, hazard, and impact of a bushfire, and in doing so reduce the potential for loss of life and property. Watch the video below for more explanation.

What can hazard reduction burning achieve in Australia?

According to Dr Andrew Sullivan, leader of CSIRO’s Bushfire Behaviour and Risks team, hazard reduction burning by itself is not a panacea.

“There’s no ‘solution’ to bushfires,” says Dr Sullivan.

“Fire is an integral part of our land, essential to many of our ecosystems, so instead we need to employ multiple approaches that can help mitigate the threat without creating new problems. Hazard reduction burning is just one of a suite of tools that we use in fire management. But it significantly improves our ability to manage wildfires when they do occur.”

When the weather conditions are extreme, our ability to manage fires becomes very limited and the effect of hazard reduction efforts decreases. But hazard reduction burning lengthens the window of opportunity for effective action when fires are controllable and increases the ability of emergency services to safely suppress a fire before it becomes uncontrollable.

Where hazard reduction burning has been carried out, we know that it slows the spread of fires, reduces their intensity, and lowers the potential for spot fires.

What are the complexities?

The success of hazard reduction burning is influenced by many different considerations, including economic, environmental, social and management.

The diversity of Australia’s landscape makes it difficult to reliably extrapolate and apply knowledge gained in one region to another.

The window of opportunity for conducting effective hazard reduction burns in the right conditions – taking into account wind speed, temperature, humidity and rainfall – varies from one part of the country to another and is decreasing as a result of climate change. Similarly, the type and amount of fuel and the subsequent effect of a burn on fuel hazard and any wildfire that may impact it varies with the prevailing conditions and location.

In order to conduct effective hazard reduction burning, we need practitioners who are not just well-equipped and experienced, but who also have extensive local knowledge. While it’s possible to share best practice, there is no one-size-fits-all solution that can be applied to the whole country.

The costs of hazard reduction burning as well as the benefits also need to be weighed. Even successful controlled burns can have significant impacts on surrounding communities and infrastructure – from individuals with respiratory illnesses to agricultural production and ecosystems.

“That’s especially true when you’re looking at how often a hazard reduction burn should be carried out to maintain a given level of hazard,” says Dr Sullivan.

“The ideal return interval for effective hazard reduction may be at odds with the ideal return interval for the health of an ecosystem, so we have to consider the trade-offs. Is it better to have a planned burn, in which case we know there will be moderate impacts; or do we choose not to do a hazard reduction burn, but then run the risk of more extreme impacts from a wildfire that may or may not occur? There isn’t always a clear or easy answer so the decision will depend upon the specific ecosystem, situation and level of risk.”

One of the challenges for fire managers is a lack of reliable models or case studies that focus specifically on quantifying the effect of hazard reduction burning on fuels and the effect of hazard-reduced fuel on wildfire behaviour under real-world conditions. Such studies – especially if they recognised the costs as well as the benefits – would support more informed decision making in this space.

Rural firefighters conducting hazard reduction burns underway before summer bushfire season. Sydney, Australia - 17 October 2020. Image/Shutterstock

Hazard reduction burns underway before summer bushfire season. Sydney, Australia – 17 October 2020. Image/Shutterstock

What is the intersection between hazard reduction burning and cultural burning carried out by Indigenous people?

Indigenous people in Australia have used fire to manage land for many thousands of years.

Cultural burning involves manipulating fire to create mosaic of burned patches across the landscape, with practices carefully tailored to protect designated features of the ecosystem. It generally takes place on a much smaller scale than a hazard reduction burn.

While cultural burning can achieve some level of hazard reduction, it’s often done for ecological or cultural purposes such as hunting, creating pathways, removing invasive species or Ceremony.

Although cultural burning is about more than just hazard reduction, it may still have a role to play in building resilience and increasing our efforts to mitigate risk from bushfire. In one recent project, CSIRO worked with Indigenous fire experts to design landscape burning partnerships, projects and activities across Australia. This led to two-way knowledge exchange and the incorporation of cultural burning practices into Western land management practices.

What work is CSIRO doing to inform hazard reduction burning practices?

CSIRO has been providing cutting-edge bushfire research for the last 70 years, enabling a broad range of stakeholders – from government agencies through to frontline firefighters and the general public – to make informed decisions about bushfire preparation, fire response and suppression, and disaster resilience.

scientists and CFA in high viz gear heading into bush

Science and knowledge: educating communities and preparing for bushfire is a collaborative effort.

Specific work has included:

  • producing guides in specific fuel types for safe and effective hazard reduction burning for use by land managers
  • developing a smoke hazard prediction tool to help guide planned burning in sites with high value or vulnerability and to minimise public impact
  • developing a national bushfire hazard planning map to improve bushfire prevention and preparation
  • development and refinement of fire behaviour models for important vegetation types including eucalypt forest, croplands, mallee-heath and shrublands that aid understanding of effect of fuel management
  • design and construction of a next generation bushfire spread simulation framework called Spark that was recently selected by AFAC to be the basis of the next national operational bushfire simulator, and which can be used to quantify risk spatially to prioritise regions for hazard reduction and other fire management actions
  • training and aiding of national fire behaviour analysts who undertaken prediction of wildfires for early warning of the general public and suppression planning


  1. A look at time line historical vegetation reduction and increasing heat due to lack of vegetation, tree reduction clearly indicated the increase frequency of fire and human induced fire/heat outputs are doubling the out of control fire risk.
    Reduction burning included in this, has also resulted in some of the most extreme fire in Australia’s history. Example is the 1994 Bundeena fires started as a hazard reduction at Heathcotte National Park.

    Bush fire hazard reduction burning is absolutely fruitless and increases the risk of fire. It loads up CO2 in the atmosphere, increasing the thickness of the air and absorption of heat, sending us closer towards a “Venus” like atmosphere.
    There was no bush fire reduction burning during the Earths period of transition from water based life to increased oxygen levels in the atmosphere, then land based animals and plants.

    Land base plants set sequestrated CO2 towards a rich oxygen atmosphere. Absolutely zero scientific research over genuine time scales to prove back burning is of any benefit to reduction of CO2 and subsequent reduction of heat and therefore the medium to long term fire risk.

    All fires destroys tree saplings, so frequent burning obviously in excess of the natural fire events one would expect from lightning or natural source (this does not include aboriginal intervention, they are human and very much have reduced vegetation across Australia over the 40,000 years of habitation), has led to deforestation generally.
    The absolute stupidity of this knee jerk reaction from people across the country, including CSIRO here lording backing burn practices, each and every time there is a severe fire, is beyond comprehension.

    If we genuinely wish to reduce heat dry air drought and bush fire potential we need more trees not less. Trees account for 50% of rain over land and 90% of rain inland.
    Given this fact; how does increased frequency of fires and CO2 production possible equate to lower temperature and “term” strategy for fire reduction?
    The strategy is simple. Human structures, concrete, earth covered dwellings, with more vegetation, fire breaks in town planning by; open space oval and parks in town peripherals,
    Then water supply system for consumer mains surrounding homes and the built environment with fire sprinkler automated systems to stop the intrusion of fire storms to the city center. around the edges of habitats.

    Bush home on farms and the like earth covered and concrete pre-cast which is in fact prefabricated and economic, more durable, lower maintenance, zero termite risk and very very low fire risk.
    When are people going to take control and responsibility for their own habitats and actions?
    Develop, not fire resistance but fire proof housing structures for our own protection. Lower heat absorption sources and fire origins to cool with tree planting and vegetation protection while looking after ourselves, protect the whole of the environment.
    The solution is to take responsibility, Do not just carelessly burn animals and plants in this insidious knee jerk reaction each time there is a more and more severe fire episode. Constructs that are fire proof with water system town water used for fire protection, peripheral open spaces around town cities, protect, conserve forest and the essential sequestration mechanism, plants. Lower the frequencies of fires to mimic natural cycles, more like 10 to 20 year cycles not yearly back burns. This will result in increased vegetation (tree create rain) cooling sequestering CO2.
    The most common phone call to the Government the Council, Department of Environment from the novice and scared uneducated individual is; “We need more back burning we just had a scary fire”.

    This reaction is short sighted and completely wrong knee jerk.

    1. Not sure how a pest inspector is sufficiently qualified to make such claims. Your lack of knowledge in this field is made quite evident every time you mentioned a “Back Burn”. Ms Dawkins has done an excellent job conveying the fact that reducing fuel loads can minimise the intensity of Wild Fire events. Over 20 tones per hectare of small particle fuel burning is not able to be stopped by any human intervention, and will destroy the forests. At 5 tones it is manageable, the fire will not crown as easily and there will be some surface ‘Duff’ remaining to keep soil in place. Reduce the fuel load with low intensity ‘Hazard Reductions’ and you will maintain large trees with thick canopy. Where successive Wild Fires have occurred there are NO significant trees that have survived. There are many examples of total destruction due to high fuel loads (and catastrophic weather conditions) and also reduced fire intensity as a result of responsible fuel management practices in the Bilpin/Kurrajong Heights area. Come with an open mind and have a look.

    2. A lot of uninformed stuff in there, with a sprinkling of common sense.
      Houses built in the urban/bush interface should have better fire protection.
      In every major fire where many houses have been lost, there is usually a single house that survives relatively unscathed.
      Because they have been well prepared.
      Ive talked to a few of these owners, and an investment of about 10k was required to survive.
      However, few people are prepared to add that cost to their home for something that they may never actually need. There are also ongoing maintenance items and costs involved that most people will baulk at.
      There is still a perception amongst many that if a fire happens, a fire truck will turn up and save their property regardless of how well they have prepared.
      Hazard reduction has proved to be effective. However there just isnt the number of people available to complete the work in the time available.
      The restrictions on smoke that incur no burn days need to be removed.
      What is worse?
      A little bit of discomfort for a while, with no houses or lives lost, or a lot more smoke, a lot more discomfort, possible evacuations, and sadly the loss of life.

      Your knowledge on the subject is fleeting at best.
      In some respects, the CSIRO is clutching at straws, but a lot of their science is sound.
      I think it was Phil Cheney that developed a lot of the helpful information.
      From memory, he was possibly the last scientist to conduct proper research, and not only look for answers to fit a corporate agenda.

  2. Very informative

  3. I read this article with great interest, not from an academic background, but as a landholder who has faced the fire. Our small community of 22 properties, west of Laguna in the Lower Hunter, is nestled on the eastern boundaries of Yengo NP. The charred remnants of my western fence marks the confluence of the Little L and Gospers Mountain fires of December 2019. A somewhat lamentable honour. Our landholders experienced the impact of both bushfires simultaneously. Able bodied members of our community banded together into an ad hoc fire crew, standing shoulder to shoulder on the fireground with the RFS and New Zealand brigades. One house succumbed, along with numerous sheds, bridges, fences and other assets. Habitats and wildlife were decimated. But, ours was not a firestorm. Unlike some communities, we had no strong winds and limited crowning in the valley itself.
    Our experience galvanised the community into becoming better prepared to mitigate the onslaught of future fires that climate change will surely deliver. The lessons learned on the fireground, coupled with our intimate knowledge of our landscape, eco systems and the behaviour of the 2019 fires in our valley, provide valuable insights into the challenges that all communities face. There is a critical need to explore alternative methods for managing our native forests in the hope of reducing the prevalence of catastrophic fire on critical habitat, fauna, human life and assets. Our landholders association was formed to unify our small community and to help legitimise our efforts to understand the challenges and to develop new ways to appropriately manage our lands as contemporary custodians, similar to how the aboriginal population did for thousands of years. If separated from the cultural significances, aboriginal land management practices, that utilised low intensity mosaic burns, were by today’s standards, ecological burns. Different to the broad scale, hotter and less controllable Hazard Reduction burns undertaken by the RFS and other agencies. The notion that thousands of hectares of government controlled native forest can be successfully managed, by any means, is unrealistic. There is neither the resources, human, technical and financial, nor the legislative commitment to do so. The scale is simply too overwhelming.
    Surely the solution is to define achievable lines of defence, closer to home. Identifying manageable, defendable buffer zones and harnessing the principles of symbiotic mosaic burns to keep fuel loads within controllable limits. Well managed ecological burns could dramatically reduce the chances of catastrophic fires, crowning and the devastation those fires reek on the native environments. And logically, not on ridges and rising slopes, but where fires will slow on decent. This is particularly relevant where the most likely source of threat can be identified. In our case, the western and northern boundaries with Yengo NP, where fires in our valley historically emanated.
    Our association has received funding under the NSW BLERF programme, to explore methods and protocols to help better manage our bushfire threat. Money to survey our dozen or more vegetation communities, map and construct manageable containment lines, develop and test low intensity ecological burning practices (Symbiotic Mosaic Burns), survey and support our native fauna, upgrade access and communication and, very importantly, document and share our experiences to help other communities to explore their own circumstances and potential mitigation strategies.
    Unfortunately, we have encountered one massive impediment, the current legislation. Whilst government controlled forests represent the greatest threat to life, vegetation and assets, the shear scale of their holdings places any realistic solution far beyond their reach. But as landholders, the contemporary custodians of our lands, it seems we are prevented from taking action for either a minimum of seven years after a fire event or indefinitely, depending who you talk to. Fires that ignite crown land, most commonly become the community’s problem. As was Little L and Gospers for us. And yet, our determination to defend and protect our native landscape and human assets, is hamstrung by an inability to pre manage a potential catastrophe in any meaningful way. This must change. The current La Nina that has spawned explosive regrowth, will turn again and what is lush and green today, in a few short years will be fuel on the ground for the next lightning strike, somewhere beyond our fences in the park beyond.

    I would welcome feedback from anyone with experience and knowledge of bushfires in Australia. We are not experts and any little bit of qualified advice helps.

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