Greater use of small planes, helicopters and drones in prescribed burning in order to achieve safe and healthy landscapes. As outlined in The Truth About Fuel Reduction Burning on the WA Bush Fire Front website, real data gathered from almost 60 years of historical data from the forests of southwest WA unequivocally shows that when the area of prescribed burning trends down, the area of uncontrolled bushfires (wildfires) trends up. There is a simple explanation: bushfires are more difficult to put out in long unburnt, heavy fuels.
Prescribed burning is important in reducing fuel loads and is undertaken periodically, is a milder burn/aiming to minimise crown scorch and usually only burns a portion of an area. It can be called prescribed burning, hazard reduction burning, controlled burning or ecological maintenance burning.
Prescribed burning can use ground and aerial prescribed burning, the latter using aircraft to drop small incendiary capsules on a grid spacing that allows for mild burns and covering large areas safely.
The mild burns are designed to join up late in the evening where conditions are cooler and the grid is designed for that to occur. It is important that flame heights are kept as low as possible and there are unburnt patches remaining.
An early aerial burning technique used a ping pong ball containing potassium permanganate, which was injected with ethylene glycol at time of dropping the capsule from a fixed wing aircraft. Current large-scale aerial burning such as undertaken by the Australian Wildlife Conservancy uses small flexible capsules containing potassium permanganate, automatically injected with ethylene glycol. The capsules ignite 25 to 30 seconds after being injected.
It is important that prescribed burning is completed as safely as possible, in the right conditions and time of year. As advised by a bushfire expert, a fundamental rule for undertaking a burn is you don’t light up before noon or until you know the wind strength and direction has stabilised for the day and the burn is carried out on a decreasing Hazard.
Important points in regards to the use of aero burning aircraft, helicopters and drones for prescribed burning:
- Means prescribed burning can be undertaken on a grid pattern where flame junction points are reached at nominated end of day when conditions are cool.
- Specific topographic features, such as long unburnt ridges and high points that could cause long distance spotting, can be selectively targeted in either fuel reduction or bushfire control operations.
- Increases the area that can be hazard reduced using mild burning.
- Optimises hazard reduced area in the cooler periods or where required.
- Reduces human safety risks.
- Sets up the process for establishing safe and healthy landscapes.
- Allows use of this technology to backburn large areas between a bushfire front and containment lines.
Using incendiary capsules with light aircraft technology has been carried out for more than 50 years.
Incendiary capsules were dropped from a light aircraft near Bega in the South Coast Fire Prevention Scheme region in 1968 on planned grid patters to minimise scorch, as outlined in the photo below.
This work was organised by foresters from the NSW Forestry Commission, with areas of 4,900 and 5,700 hectares being burnt on grid patterns.
I looked after the Hume Snowy Bushfire Prevention Scheme for 4 weeks in 1980 whilst the OIC was on leave and completed 4 aerial prescribed burning operations. The Hume Snowy Bushfire Prevention Scheme was responsible for fuel reduction burning in Kosciuszko National Park and some areas outside, managed by the then Forestry Commission. I also organised two aero burning operations on Maragle SF in 1983, of the order of 4000 hectares plus, in very high fuel load forests (through the Hume Snowy scheme). All of the burns were on planned grid patterns, and achieved mild burning, with minimal scorch. This early experience taught me the value of this technology.
New technology is assisting in increasing safety and efficiency of prescribed burning programs. As noted in Forestry Corporation’s drone trials to make hazard reduction burning safer dated 6 June 2019, Forestry Corporation of NSW has been trialling drones for aerial ignition to better understand how this emerging technology can support a safe and effective hazard reduction burning program.
Recent trials in Benandarah State Forest, north of Batemans Bay, have shown drones can effectively ignite hazard reduction burns in hard to access areas. This ultimately means less risk to forestry staff and better bushfire protection for neighbours and forest assets. Multiple gridded ignition points mean that fires don’t reach high intensities before they run into the next fire. Burns are kept cool to create better mosaic patterns, which is good for ecological diversity. Drones have huge potential to complement existing hazard reduction practices, said Forestry Corporation Protection Supervisor, Julian Armstrong.
“We used the drone to deliver incendiaries to the target sites, which would have otherwise been difficult and dangerous for staff to access,” Mr Armstrong said. “Drones meant we could safely carry out the burning program over a wider area, removing fine fuels in a mosaic pattern for a safer and healthier forest. “The trials are not about replacing staff but will mean staff can work in a safer environment.” The results showed that over the two-day trial, double the area could be burnt using the drone incendiaries for ignition.
“Forestry Corporation ground crews concentrated on lighting the burns from road lines, while drone incendiaries were used to light ridgetops, remote areas and tricky areas such as around power lines,” Mr Armstrong said. “The drone is equipped with infra-red technology so we could see where the fire front was slowly burning, even through smoke.
“This was a first for us, and we are really happy with the results – we look forward to running more trials of this technology in the current burning season.
“We’ll build on these learnings, and ultimately will have a clear picture on drone incendiary effectiveness, management and cost-effectiveness in this space.”
The drones were operated by Civil Aviation Safety Authority-certified drone pilots according to a prescribed burn plan.
Considering one important state only, the available NSW data confirms inadequate prescribed burning in general and across landscapes. The fuel reduction burning areas in NSW between prescribed burning in NSW in the years 1999-2003 were 355,507; 441,989; 436,369 and 432,630 hectares/ year, considerably higher than recent times. The average annual fuel reduction burning in NSW between 2010 to 2019 was 153,291 hectares over 27 million hectares of forest in NSW. This equates to 0.57 % of forested areas hazard reduced per year and only 2.8 % over 5 years, very low rates. In 2019/ 20, the fuel reduction burning figure in NSW was 34,000 hectares, this equates to 0.13% of forested areas hazard reduced by burning, albeit a dangerous bushfire year.
At the state level, I suggest that we as a state can increase annual prescribed burning area, effectiveness and safety outcome in NSW using light aircraft, helicopters and drones to improve efficiencies and areas of prescribed burning, reducing high current fuel loads. I suggest that it would be beneficial for government, government agencies, local government, communities, rural landowners, contractors and applicable private sector to work through all potential opportunity areas to increase safe aerial prescribed burning across forested areas of NSW. The safety of NSW communities, infrastructure, forests, water quality, waterways, fauna, flora, fish, air quality and heritage sites depends on this.
John O’Donnell was a forester with the then NSW Forestry Commission for 11 years. He holds a Bachelor of Science (Forestry) Hons 1978 from Australian National University and a Post Graduate Diploma in Agronomy and Farming Systems from the University of Adelaide 1996 and 1997, majoring in environmental issues in agriculture. He was awarded a Commonwealth Forestry Scholarship in 1976 and 1977.
