Hazard Reduction - Why Is It Important?

Australia's unique climate and geography have always made us vulnerable to extreme weather events, but climate change is exacerbating those conditions even more.

We are seeing more severe and frequent bushfires, putting unprecedented strain on communities and response teams, and resulting in significant social, environmental, and economic consequences.

In such challenging circumstances, we must employ a variety of risk-reduction strategies. One of these tools is hazard reduction burning, which has a significant role to play in fire management throughout Australia.

What is hazard reduction burning?

When bushfires occur, their behaviour is determined by three factors: weather, terrain, and fuel. Fuel, or fine combustible vegetation and debris such as dry grass, dead leaves, bark, and twigs, is the factor on which we have the most direct influence.

Hazard reduction burning is the deliberate, controlled use of fire in the landscape under low-risk conditions to reduce the availability of fuel for a bushfire.  Hazard reduction burning is just one type of prescribed burning, which can be used for a variety of purposes. These include removing post-harvest forestry debris, preparing the site for seedling regeneration, cultural reasons, ecological management, and biodiversity habitat management. Each of these will have some effect on reducing bushfire risk, even though that is not their primary goal.

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

When used in conjunction with other fire management approaches, hazard reduction burning can reduce the intensity, hazard, and impact of a bushfire, lowering the risk of loss of life and property.

What can hazard reduction burning achieve in Australia?

According to Dr Andrew Sullivan, leader of the CSIRO's Bushfire Behaviour and Risks team, hazard reduction burning is not a cure-all.

"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 is extreme, our ability to manage fires is severely limited, and the effectiveness of hazard reduction efforts decreases. However, hazard reduction burning extends the window of opportunity for effective action when fires are controllable, allowing emergency services to safely suppress a fire before it becomes uncontrollable.

Where hazard reduction burning has been used, we know that it slows the spread of fires, reduces their intensity, and lowers the likelihood of spot fires.

What are the complexities?

Many factors influence the success of hazard reduction burning, including economics, the environment, society, and management.

The diversity of Australia's landscape makes it difficult to extrapolate and apply knowledge from one region to another.

The window of opportunity for conducting effective hazard reduction burns under the right conditions (wind speed, temperature, humidity, and rainfall) varies across the country and is shrinking as a result of climate change. Similarly, the type and amount of fuel used, as well as the impact of a burn on fuel hazard and any wildfires that may occur, vary depending on the conditions and location.

Effective hazard reduction burning requires practitioners who are not only well-equipped and experienced, but also have extensive local knowledge. While it is possible to share best practices, there is no universal solution that can be applied across the country.

The costs and benefits of hazard reduction burning must be carefully considered. Even successful controlled burns can have a significant impact on nearby communities and infrastructure, ranging 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.

How is this being implemented?

Hazard reductions often come in the form of controlled burns by the RFS and landowners, but a former Queensland Parks and Wildlife Services ranger has come up with an interesting idea.

While fuel loads in National Parks have been blamed for igniting some serious fires in recent months, Neal Gathercole has detailed how a grazing programme in Central Queensland alleviated a major issue.

Neal Gathercole was the former ranger-in-charge of the Queensland Parks and Wildlife Service's Clermont area, and he helped establish a grazing programme in the Nairana and Mazeppa National Parks, as well as the Belmah Conservation Area.

The parks were purchased in the early 1990s to protect the brigalow, blackwood, and gidgee woodlands.

Mr Gathercole stated that fires were common in national parks, with the majority of them caused by buffel grass that had grown without being grazed.

“After the parks were destocked, we found the buffel grass loads were way too high and when you had a fire it was devastating the key values of that brigalow scrub community. You could have 10-12t/ha of buffel grass under that scrub and nothing can survive under that intense fire."

While all three parks had previously experienced bushfires, two major fires in the Nairana National Park sparked the reintroduction of grazing.

Since the cattle were introduced to the National Parks, Mr Gathercole said the improvement in fire management and ecosystem health were noticeable.

Mr Gathercole said it was not a solution for all National Parks.

“You might have a park with wetland habitats and you might not necessarily want hard-hoofed animals walking through it,” he said.

‍

(Sources: Beef Central and CSIRO)