Western Australia: Improving mitigation

How prescribed burning is making its (successful) mark

There’s been much debate in the news lately following the extensive bushfires in NSW and Victoria this summer of 2019/2020.

It would appear from examining the context of the fires that prescribed burning and other mitigation actions are not used to the same extent as has been happening in Western Australia for the past several decades or so.

Fire scientists have been very active in researching the causes and the management of bushfires and have published the results. Whilst the forests in south west WA are endemic to the area, the general principles discovered in the WA research can, with adjustments for different fire regimes, be applied in other bushfire prone areas of Australia.

Two of these bushfire researchers recently wrote the following essay which explains why we need to carry out prescribed burning wherever we have forests and woodlands. The authors are Neil Burrows and Rick Sneeuwjagt and here is their essay. A must-read.

Neil Burrows makes the keynote presentation at the AFAC Conference held in Perth in September 2018.

Out of frustration Rick and I have written the piece below to counter some of the nonsense that is circulating from people who have no understanding or practical experience with fire behaviour, prescribed burning and bushfire suppression. Between us, Rick and I have more than 80 years experience in bushfire science, policy, planning, prescribed burning and fire suppression. The piece is lengthy but its a complex issue.

How and why prescribed burning mitigates bushfire losses

Neil Burrows and Rick Sneeuwjagt

The piece by Byron Lamont and Tianhua He titled “Why prescribed burns don’t stop wildfires” (WAToday 22 January 2020) is complete fiction. It reveals that these authors have no experience or operational understanding of fire behaviour, prescribed burning and bushfire suppression. Their baseless and inhumane opinions, if given any credibility, will give rise to very dangerous fire management policies, a continuation of a cycle of devastating bushfires and further losses of lives and beautiful forests.
The title of their article is a clue to their lack of understanding. Prescribed burning is not designed to stop bushfires. It is designed to make them easier, safer and cheaper to suppress. Experienced land managers, fire fighters, and the bushfire scientists who work closely with them, are in no doubt that the scientific, experiential and historical evidence demonstrates that prescribed burning, done properly, is highly effective at mitigating the bushfire threat, even under severe weather conditions. This is based on the following evidence.
Firstly, fire science. Reducing fuel loads and simplifying fuel structures by regular burning reduces the speed of a bushfire, its intensity (heat energy output), the size of the flames and its ember and spotting potential. All of this makes bushfires less damaging and easier to put out. In mature forests, crown fires cannot be sustained if the surface and near surface fuels are at low levels as a result of regular fuel reduction burning.

Lamont and He make the extraordinary assertion that long unburnt forest fuels are of low flammability and therefore of no significant threat to communities. This is not only demonstrably untrue, it is dangerously wrong. For example, in long unburnt karri forest, much of the live, green understorey dies and becomes dead, dry fuel on the forest floor after about 25-30 years. Bushfires are most likely to occur well before that time. Dead scrub, together with accumulated dead leaves, twigs and bark, the surface and aerated near-surface fuels can be a meter or more deep with total fuel loads of up to 50 tonnes per hectare. In dryer stringybark forests, the sparser, lower understorey vegetation comprises a small component of the total fuel complex. It is the accumulation of dead fuels (leaves, twigs, branchlets, bark) that drives forest fires. This is because it is at the base of the ‘fuel ladder’, it is dry, and it reaches very high loadings if left unburnt.

Second, real-world experience. We know of hundreds of examples where prescribed burning has ‘saved the day’

. Hot fires ran into areas of low fuel, and the resulting reduced fire behaviour enabled fire fighters to gain the upper hand. Conversely, we can cite numerous recent examples where a lack of prescribed burning has resulted in unstoppable fires and considerable losses. Ask any fire fighter whether they would rather fight a bushfire in 4 year old fuels or in 40 year old fuels? We know what the answer will be. Academics like Lamont and He disdain the experience of bushmen and experienced firefighters, preferring computer models developed on a green, leafy campus. In doing so they reject the experience of real-world Australians and their experience over the last 200 years.

Third, history. There are almost 60 years of historical data from the forests of south west WA, and these data unequivocally show that when the area of prescribed burning trends down, the area burnt by bushfire trends up. There is a simple explanation: bushfires are more difficult to put out in heavy fuels. The area burnt by wildfire escalates rapidly when the area of prescribed burning in a region falls below about 8% per annum. Burning about 8% per annum results in about 40% of the bushland carrying fuels 0-5 years old.

A very powerful factor in the recent bushfire tragedies in NSW is the fact that prescribed burning in NSW has amounted to less than 2% per annum. This means only 10% of the bushland is carrying fuels 0-5 years old and 80% is carrying fuels older than 10 years. This is well below the threshold for effective bushfire mitigation because a high proportion of the region is carrying very old, heavy, flammable fuels. Fires in these fuels rapidly become unstoppable, especially when they have been dried out by years of drought.

Finally, strategic planning. To be effective, prescribed burning must also be strategic – that is, done in the right places to protect communities by intercepting fire runs under the worst fire weather conditions. The fire management cells need to be large enough to ensure a sufficient area for the spread of a bushfire to be slowed and controlled. Burns must be bounded by roads or tracks to enable rapid access by fire fighters. Burning must be done to appropriate standards of fuel removal and fire intensity. Prescribed burns that are too patchy may not slow a bushfire, and in some forests, burns that are too hot can stimulate the regeneration of dense scrub.

Prescribed burning – how and why it works
The purpose of a fuel reduction burning program is not to stop bushfires, but to assist with their safe suppression. The process of bushfire suppression is complex and dynamic. There are a variety of suppression strategies and tactics that can be used in space and time, depending on weather conditions, fuels, topography, fire behaviour, fire shape and fire position in the landscape, and fire intensity around the fire’s perimeter.
Fire fighters rarely make a direct attack on the head fire – it’s usually too ‘hot’. Instead, they implement other strategies including a variety of direct, indirect and parallel attacks – the options, and likelihood of early success, are greater if the fire is burning slower and at a lower intensity because it’s burning in young, light fuels. Appliances such as water bombers will be more effective on slower moving, lower intensity fires. Fire intensity varies around the fire’s perimeter, affording suppression opportunities – there will almost always be a place on the fire’s perimeter that can be attacked – even under severe fire weather conditions – and if fuel loads are low, this opportunity widens significantly.
The most trying bushfire situation occurs when there is wind shift and the long flank of the fire becomes a wide head fire. Therefore, containment work on the ‘pressure flank’ is critical and is more likely to succeed in young, low fuel situations when flank fire intensity is relatively low, even under severe weather conditions.

If part of the fire is burning in very light fuels as a result of prescribed burning, then if resources are stretched, it can be ignored and resources deployed to higher priority areas around the fire perimeter, or to defending properties, or dispatched to other fires in a multiple fire situation.

Prescribed burning provides ‘anchor points’ and ‘tie in’ points for fire fighters. These low fuel areas are very important for indirect suppression strategies including back burning. Attempting to back burn in old, heavy fuels against old, heavy fuels is a slow, resources demanding, dangerous and risky process. Back burning in young, light fuels surrounded by young, light fuels is much safer, more likely to be successful and requires less resources. Low fuel areas are also very important for ‘tying in’ containment lines, enabling faster, more efficient suppression. The speed of construction of containment lines is crucial in the battle against a growing fire. Fire suppression is a race in terms of rate of fireline construction and containment verses rate of perimeter growth of the bushfire. Fires burn slower in younger, lighter fuels, not only improving the likelihood of early detection and suppression, but increasing the odds of fire fighters getting the upper hand.

Severe fire weather fire weather conditions don’t last very long in the life cycle of a bushfire – when diurnal fire weather conditions ease (and they always do at some point), and if the fire is burning in young, light fuels, there is a larger window of opportunity for safe suppression, than if it’s burning in old, heavy fuels.

There are two other critical ways in which fuel reduction programs assist with bushcontrol. The first is that it allows fires to be suppressed in the lead-up days to extreme conditions. Firefighters are nearly always overwhelmed when ‘catastrophic’ conditions (i.e.hot, dry, windy weather) strike fires that are already burning in the landscape. The presence of low fuel areas makes it more likely that these fires can be controlled before the catastrophic conditions occur.

The second is that when there are multiple fires on the same day, as occurred during the Cyclone Alby crisis in WA in 1978, fire controllers can set up a “triage” response. Fires burning in 1 or 2 year old fuel can be temporarily ignored, while all the focus is placed on the most threatening fires. This allows the best use to be made of resources.

Regardless of fire weather conditions, to firefighters, fuel load matters. It directly affects fire intensity (heat energy output) around the fire’s perimeter, and the size of the suppression windows in space and time. Also, containment line break outs such as hop overs and spot fires, are much easier to control in light fuels than in heavy fuels.

The fuel load burning behind the flame zone, which is greater in older fuels, is critical for suppression difficulty because total heat output acts in a number of ways. It is an input to convection which increases wind speeds in the flame zone, boosting spotting and fire behaviour. It increases the likelihood of high energy release rates and deep flaming, conditions that can trigger a transition to a dangerous and unpredictable plume-driven fire. It increases the likelihood of re-ignition and breaching of the containment line by burning across it or by blown embers or by hop-overs. Radiation from glowing combustion adds to the heat load on firefighters and increases the time that the burnt ground can be used for safe refuge. It substantially decreases the effectiveness of water and other suppressants /retardants applied from the ground or from the air. Heavy fuel also hinders fire line construction and in some fuels make it impractical.

Of the elements that make up the bushfire triangle – fuel, weather and topography – only fuel can be managed. But this must be done the right way – underpinned by good science, well planned and well executed by trained, experienced people who are well resourced. Prescribed burning is costly and comes with an element of risk, but the alternative, a cycle of bushfires, is far more costly to communities and the environment.

Conclusion:

The article by Lamont and He in WAToday is not only factually incorrect, it is dangerous and inhumane. If the authorities were to take any notice of their assertions, and curtail the fuel reduction program, the result in WA would be identical to that currently occurring in NSW: death, destruction, heartbreak. Our advice to Lamont and He is to get some actual fire experience in the bush, get on the back of a fire truck, and then lets see what they think about the value of fuel reduction in assisting with bushfire control.

Neil Burrows sums up the pros and cons of prescribed burning at the 2018 AFAC Conference.

Make a difference

Little things count as to whether your house burns or not

With the hot weather coming in a few short weeks it is time to check over the house and our surrounds, including our gardens (if we have them), to ensure they are at low risk of catching alight.

In view of the need for helping residents to be at lower risk from bushfires, back in March 2019, a group of us with the support of Senator Linda Reynolds and Member for Forrest MP, Nola Marino, decided to conduct an event that would help residents in bushfire-prone areas making themselves and their properties safer.

On Sunday 1 May 2019 we had a morning Firewise Excursion. We were delighted that Mrs Nola Marino was able to attend and contribute to the discussion. We started with a scene-setting exercise of exploring the differing facets of bushfire in the South West: its high frequency, how to prevent embers from entering into roof spaces, etc. We used a series of seven posters each of which highlighted an aspect of the problem.  Here is a link to the Gardens0fFire_series Poster exhibition which drew on the rather sombre book by Robert Kenny who had his house destroyed in the Victorian Bushfires of 2009.

The Excursion was named as being “Firewise“. This is derived from a program of this name developed in the US by the National Fire Protection Association (NFPA).  House and garden design that aims to reduce bushfire risk is crucial as is re-engineering existing houses and gardens to protect against ember attack and, occasionally, direct flame contact.

The Firewise concept was developed out of the research work of wildfire scientist, Dr Jack Cohen, who studied the aftermath of many wildfires and in particular the way a house will burn down. Contrary to popular belief it is not a great wall of flame, rather it is the embers getting into nooks and crannies around a house, including vents, and smouldering then erupting into flames and burning the house down from the inside. He stresses the need for defensible space near the house which is kept at very low fuel levels to ensure embers are not created there, there is nothing to burn and there is little chance of direct flame attack.

The scene setting exercise was useful as it stimulated a lively discussion about the many different aspect of what can be done by residents and fire authorities to make everyone safer.

We had short summary papers which contain online links to further information.  These are: Firewise excursion Intro and Firewise excursion Parkland.

We then had a break in the weather and were able to see Yarri Park as an example of Parkland Cleared.  See the “before” image, below.

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Yarri Park.The large trees are a eucalypt, Eucalyptus patens, or Yarri which grow only in favoured spots in the South West – high rainfall and deep soils – such as here in Balingup. This is the “before picture” showing high buildup of understory which when dried out becomes a bushfire risk. 

Here is the Park after a full week of activity to clean out much of the understory, make the Park easier to walk through and to maintain as well as being at a lower risk of bushfire to surrounding neighbours.

YarriPark_After_15Nov16

The “after picture” showing Parkland Cleared result.

We then headed out to an attractive property which used to be Birdwood Park near Balingup townsite which is a good example of a property being made to be at low risk of bushfire attack. Considerable quantities of vegetation were removed and any trees near the house were usually deciduous or were at the low end of the flammability scale, eg Indian Hawthorn, Raphiolepis indica, and Coprosma or Mirror Bush.

Then the next front came through and we dashed back to the Fire Shed or headed home.

Some more ideas about Firewise_Property_Design_Sep19 are contained in this document. There are links to further material in this to follow up should you want to know more.

Even removing the layer of mulch that you spread carefully in that garden bed next to the house could make you safer. It would mean that embers would fall on bare ground instead of potential fuel. A few small changes like this could make the difference.

Wattles are worse*

Wattles are often added to a property to provide shade and possibly firewood for later. Whilst the smaller shrubby ones are easy to remove when they become scraggly and start to die back, the larger trees such as Cedar Wattles, Black Wattles and Blackwood Wattles cause a whole lot of problems as they age.

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Overall scene showing the fallen trunk of a Cedar Wattle which fell across the path to the hillside. It damaged the fence, pushed a strainer post and crushed a young Tupelo tree near the stream. In the centre of the image to the rear is a wattle in flower that shows a scar on its trunk where a large lateral branch fell off and struck the Cedar Wattle some months ago. This has subsequently fallen on Tuesday 28 August 2018

After perhaps twenty or thirty years of growth they become large trees which then will drop limbs, split or fall over entirely, damaging everything in their path.  By this time they are large trees and are costly to remove. Thus many owners are stuck in a dilemma; the ageing wattles will become more dangerous, but it is very expensive to remove them.

Here is a video taken earlier this year before the Cedar Wattle came down.

The trunk of the Cedar Wattle that fell is just behind the large post in the fence shown at the beginning.

The Cedar Wattle becomes brittle with age and branches split, but may not come away entirely.

IMG_9113

The remaining trunk of the Cedar Wattle has side branches which have split (see example near top of image). The tree has become dangerous as branches or the whole tree have become unsound. Note to the left a dead branch from another tree is suspended in the branches which could fall at any time.

The following video shows more of the ageing wattles and what can happen to them and anything in the way.

One less wattle, several more to go though hopefully in a more controlled way.

The moral of the story is not to plant them in the first place or only as quick screening to be taken out when small because they are not only a hazard with falling branches or the like, they also drop litter – leaves, twigs, pods – which add to the litter layer, being highly flammable, and will aid the spreading of bushfire in summer.

*The title has a little to do with alliteration, but it sums up some of the features of the larger wattles (acacias) which do not suit them for being near structures, not just homes but also near fences or bridges, etc.