25 January 2024

Fuel-reduction burns could make forests more flammable in the long run, major study finds

| Genevieve Jacobs
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bushfire at night

The North Black Range fire as seen from Canberra at the height of the Black Summer fires. Photo: AYMcreations.

In a finding that may turn received wisdom on its head, a landmark new study from the ANU and Curtin University has found that prescribed burning and logging may make Australian forests more flammable, not less.

The authors have issued a plea for better analysis of extreme-risk areas and deployment of rapid-response firefighting teams, controlling fires in remote areas rather than allowing them to burn out of control.

The research was conducted by the ANU’s Professor David Lindenmayer, a world expert in forest ecology, and Associate Professor Philip Zylstra, from Curtin University.

They found while prescribed burns can sometimes decrease flammability in the short term, the disruption caused to forest ecosystems by prescribed, or controlled, burning can create longer periods of additional flammability that may be more intense, particularly in remote areas.

And, the researchers say, the preference for large interventions in forest management is likely to be simplistic and grounded in a poor understanding of long-term natural dynamics.

“Very frequent burning close to homes or control lines could create defendable spaces, but large, remote and infrequent burns maintain the landscape at maximum fire risk because they undermine the natural controls that forests place on fire,” Associate Professor Zylstra said.

man standing in forest

The ANU’s Professor David Lindenmayer co-authored the study on controlled burning. Photo: ANU Media.

The authors say there needs to be a greater connection between forestry and fire science to understand how fire-prevention strategies affect the natural environment, including work with scientists who understand how forest ecosystems operate over decades.

“We’ve understood for a long time now that logging can make bushfires worse, but it’s only in the last few years that evidence is showing that prescribed burning could be doing the same thing,” Professor Lindenmayer said.

The authors found that a diverse understory of plants calms bushfires in forests by slowing the wind beneath them. If disturbance kills those taller plants, replacements regrow from the ground and cumulatively add to the fuel load.

“Fire-sensitive species thrived for millions of years because so many forests naturally create these less-flammable environments,” Professor Lindenmayer said.

“We know that old forests tend to be cooler, more moist and more sheltered. By limiting disturbance, forests can reach an appropriate age where they can be better protected from the increased frequency and severity of Australian bushfires.”

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The research includes a predictive framework for identifying areas where disturbance is likely to cause a surge in bushfire risk, enabling better-informed and targeted management strategies.

This focus on areas that are particularly high risk should also enable better and faster detection and responses, particularly in remote areas.

The authors say investment in rapid-response remote area firefighting equipment and specialists is urgently needed.

“We need to … embrace new technologies that allow us to detect fires and suppress them faster,” Professor Lindenmayer said, noting advances in drone technology and the application of artificial intelligence to detecting small fires and extinguishing them at an early stage.

“We need to be thinking about forestry and fire management in a more holistic way and look to limit actions that could be increasing flammability.”

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Philip in Narooma8:21 am 24 Jan 24

Greetings Dr Vandenbergh … Thank you for your comment. If you believe that University members are divorced from the mucky business of economic influence then you need to read the disclosure statements on scientific papers. University scientists can be strong advocates for their positions, in some cases appearing ‘one-eyed’.

If you have read the 2023 paper, then you would see that the pattern follows the 2009 paper. The discussion is more around untested hypotheses than hard facts .. quite different to what I, and you, are used to in our respective professions. As you would know hypotheses attract strong scientific debate

I am a retired Veterinarian, moving to Narooma 20 years ago. I had experience in Sudan, Ethiopia, Canada and USA before setting up a Canberra practice. I was shocked at the socio-economic levels of the far south coast and the incessant attacks on the timber industry, fishing and farming by city based, taxpayer funded extreme green conservation groups.

Having plenty of time it was interesting to thoroughly research both sides of a story. I discovered that if a William McBride or Andrew Wakefield commits scientific fraud then they will be struck off. If a government employee does the same thing they are mostly moved ‘sideways’.

I have found that there is generally more than one side to a story, and try to present a different side to the extreme green mantra if it is valid.

I have received zero dollars from my position. I am not a forestry graduate, for that matter neither is Lindemayer or Zylstra. I do NOT accuse, or imply, Lindenmayer or Zylstra of ‘massaging’ data, or accepting ‘kickbacks’

Dr Hein Vandenbergh2:51 pm 24 Jan 24

Thank you, Philip, for stating your position and interest. As I indicated, it gives greater weight to your opinion. That said, opinions do not necessarily overturn research-based fact – even if these are contested by other scientists using various other experiments to arrive at different facts. This by virtue of interrogating a different set of hypotheses. Like you, I am by no means convinced about this issue, in particular as our indigenous population – which has for eons managed the danger of devastating fires by controlled burning – does not appear to have had a voice here. Experiential knowledge garnered over eons often beats the experimental acquisition of facts garnered by scientists.
My sole remaining reservation remains your opinion that at various times – both in scientific research and third party opinionating – there has been a preponderance of the ‘extreme green mantra’. At times, conversationist groups are the only people expressing urgent and often convincing opinions while 95% of the population maintains a sullen silence. This does not warrant the label of extreme, nor that of mantra. Mantras are defined by their thoughtlesness – of that, I cannot accuse green conservationists. Thank you for stimulating this discussion. Like you, I am retired, with a medical, legal, and bioethical background. We should catch-up one day.

Dr Hein Vandenbergh3:56 pm 23 Jan 24

Two interesting opinions. Lindemayer and Zylstra can be assumed to be ‘economically neutral’ visà-vis the foresyry industry by virtue of their declared occupational positions. Philip from Narooma castigates them on the basis of a much earlier paper, but adduces no refutational argument on the current paper per se. Maybe Philip should declare his economic position. Is he an advocate for the forestry industry? His reply would carry more weight were he to declare his economic hand.

Philip in Narooma11:07 am 23 Jan 24

The paper by Lindenmayer and Zylstra, as reported in About Regional, is reported differently through AAP.

In AAP’s report ( Study warns of worse bushfires after burn-offs, logging – Australian Associated Press (aap.com.au) the possibility there are dissenting voices are raised (ie. fire and forestry authorities).

However, with even greater credibility, previous papers by Lindenmayer and Zylstra have been rebutted by peer-reviewd articles that contend some of Lindenmayer’s assertions questionable.
For instance a paper by Lindenmayer (2009) asserted that logging increased fire regimes in moist forests. This caused a groundswell of opinion that perhaps native forest logging should be abandoned.

However a paper by Attiwill et al (2013) pointed out some of the misconceptions within Lindenmayer’s work. This focussed on the moist forests of Southern Australia and showed that:
a. Of Lindenmayer’s 650 references only one Australian study was cited.
b. After a careful citation check of Australian literature, Lindemayer’s hypotheses could not be supported.

So what does this mean? Native forest logging has been abandoned in Western Australia and now in Victoria, with severe effects on some regional communities. If only one author’s opinion is used in determining the future of native forest logging and hazard reduction burns then SE NSW will suffer the consequences.

Quoting an article by Professors Kevin Tolhurst and Jerome Vanclay: “Australia has 101 million ha of native eucalypt forest, of which 5 million hectares is zoned for timber harvesting, and 78,000 ha is harvested in any year (about 0.1% of the total and 2% of the harvestable area. Harvesting from this small area supports a significant proportion of the bushfire fighting workforce and fire management resources.

Closing down native forest timber harvesting is likely to have a much greater impact on increasing bushfire severity and extent across the landscape than the increase in local fire severity claimed by the opponents of timber harvesting. A holistic, long-term and professional view of forest and fire management is needed rather than short-termed, single-issue perspectives.”

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