This article relates to the ongoing debate on Australian Rural & Regional News into Bushfires, Logging, Burns & Forest Management, in particular, into a debate into self-thinning forest understoreys and wildfire risk. The series of articles relating to this particular debate are all extracted on the general debate page.

Roger Underwood, Chair, The Bushfire Front of WA Inc, 21 October 2022

Dear Editor,

I am compelled to respond to the naïve and dangerous comments by Professor Phillip Zylstra on forest bushfire management in Western Australia, in your most recent edition.

I agree with the Bradshaw critique of Zylstra et al’s paper and I found Professor Zylstra’s defence to be unconvincing. As Professor Zylstra himself now admits, the paper’s conclusions are based on flawed methodology, thus invalidating them. I could hardly believe my eyes when I saw how Zylstra et al combined the eastern wandoo forest with the southern karri forest in their analysis, as if they were a single forest type. These forests are completely different in fuel, fire behaviour and fire ecology characteristics. One is a semi-dry, low, open and often grassy woodland; the other is tall, dense, wet-sclerophyll forest with heavy scrub. 

A further problem with the Zylstra et al paper it focuses only on ‘area burned’ and ignores ‘fire intensity’.  When it comes to fire impacts and ecosystem recovery, both the intensity of a bushfire and the area burnt are important. Bushfire-mitigation burns are designed to be of low intensity and patchy at fine scales and they cause minimal and ephemeral disruption to plants and animals. Both survive, or recover fully and rapidly. However, a high intensity wildfire can impact large areas, and cause significant damage to plants, animals and human assets; it can take decades for the bush to recover.

Professor Zylstra goes in even deeper in his latest essay. He now claims that “remote ignitions” in WA forests “may not be seen for days”, and that because WA lacks “specialist remote-area firefighters”, and because our “remote forests” are inaccessible, fires in these areas are rarely controlled using “hoses and rakehoes”. Rather, he claims, remote area fires are usually contained using backburning.

None of this is true. Indeed, it is close to fantasy. WA has an excellent forest fire detection system, using a combination of lookout towers, spotter aircraft and hot-spot seeking satellites. Ignitions are rapidly identified and precisely located. There can be occasions, after multiple lightning strikes, when a fire “sleeps” for a day or two before being detected, but this usually occurs when lightning strikes into damp, light fuels. Firefighters are well-aware of the likelihood of “sleepers” and fire spotter flight schedules are always upgraded after a lightning storm. Moreover, the modern Lightning Tracking System pinpoint all lightning strikes, whether or not they start bushfires, enabling subsequent investigation if no smoke pops up.

A greater worry for bushfire managers in the real world is multiple, simultaneous ignitions associated with a nasty lightning storm. When this occurs, you can get a situation when there are not enough firefighters to go around. It is then necessary to “triage” the response. Fires trickling around in light fuels (thanks to prescribed burning) can often be left for a day or two while suppression forces focus on more threatening fires. This is a deliberate and sensible strategy, not some foolish incompetence as Professor Zylstra might imply.

Backburning is not the preferred forest fire control strategy in WA. Decades of experience has shown that the best way to fight a forest fire is to build containment lines around it, and then mop-up the edges. I can recall only one instance in recent years when backburning was the selected strategy for a serious forest fire, and this was in the Boranup karri forest where the prevalence of sink holes made it dangerous for machines to build containment lines. I also know of situations where a fire is burning quietly under mild conditions, and a decision taken to let it burn out to existing roads, rather than put in machines to construct fire breaks. This increases the fire size, but is akin to fuel-reduction burning, and cannot be classified as backburning under wildfire conditions. Known as the “box and burn” strategy, this approach is actually being promoted in western USA these days, not just as an economic and safe way to control a wildfire outbreak, but to get in some useful fuel reduction for the future.

The idea that WA has thousands of hectares of remote, inaccessible forest is nonsense. The forests of the southwest are relatively small and well-consolidated. We have no mountainous regions as in Victoria, Tasmania and NSW. The entire forest estate has been well-roaded since the 1960s, with the forests subdivided into management blocks, all surrounded by, and in most cases traversed by, good roads. It is true that the road network in many places was allowed to deteriorate after the transfer of State Forests to National Parks, and it is also true that many of the district administration and fire management centres developed by the Forests Department pre-1985 were dismantled at about the same time. However, other developments have helped to compensate, including the fleet of fast attack fixed-wing water bombers now stationed all through the southwest. Under relatively benign conditions, water bombers can “hold” a fire in a distant location until firefighters arrive.  Parks and Wildlife do have the capability for remote-area insertion of firefighters by helicopter, and this is used routinely in the Pilbara and the Kimberley, and on one recent occasion (to my knowledge) in southwest forests. American-style smoke jumpers or rappel-crews have never been used in WA forests for the excellent reasons that they were not considered necessary, and are extremely dangerous. Many American smoke jumpers have been killed over the years, fighting fires in remote areas.

Finally, Professor Zylstra’s view that fires in the karri forest can be controlled by dropping in a handful of firefighters armed with “hoses and rake-hoes” can only be described as laughable. Firstly, hoses are only useful if connected to a powerful pump and a water supply, and these are not available in “remote” forests. Secondly, rakehoes (despite being available), were almost never used in the heavy fuels and dense scrub of the karri forest. Except in one- or two-year old fuels, they simply did not cut the mustard. In the days before bulldozers were readily available, control lines around karri fires were cut by teams of men using axes, slashers and shovels. I know, because (unlike Professor Zylstra), I was once a firefighter in the karri forest and spent many an hour on the end of a shovel constructing “spade breaks” around bushfires.  Believe me, bulldozers are quicker, safer, more effective and in the long run, cheaper. But safest, cheapest and most effective of all is to ensure the potential firegrounds are prepared in advance of any fire by systematic mild-intensity fuel reduction burning.

Also by Roger Underwood: Think fire, know fire: Roger Underwood

Related stories:

The Zylstra theory: a final comment: Roger Underwood;
Philip Zylstra’s response #4 – self-thinning forest understoreys and wildfire debate;
Jack Bradshaw to Philip Zylstra #2 – self-thinning forest understoreys and wildfire debate;
Philip Zylstra’s response #3 – self-thinning forest understoreys and wildfire risk debate;
Peter Rutherford to Philip Zylstra #2 – self-thinning forest understoreys and wildfire debate;
Philip Zylstra’s fire research: Adding value or creating risk? : Peter Rutherford;
Philip Zylstra continues the debate – self-thinning forest understoreys and wildfire risk;
Self-thinning forest understoreys and wildfire risk debate – Jack Bradshaw responds to Philip Zylstra;
‘Self thinning forest understoreys reduce wildfire risk, even in a warming climate’: Philip Zylstra responds to Jack Bradshaw;
Comment on ‘Self-thinning forest understoreys reduce wildfire risk, even in a warming climate’: Jack Bradshaw.

Philip Zylstra has responded to this article: Philip Zylstra’s response #3 – self-thinning forest understoreys and wildfire risk debate