Bushfire experts clash over logging impacts

A new report claims that past logging and wildfire disturbance had little effect on the severity of the Black Summer bushfires, prompting strong reactions from other Australian fire ecologists.

The immense scale and severity of the 2019-20 fires were devastating; they were literally record-breaking and changed understanding of how extreme fires behave. They also sparked intense interest around how we could have reduced their risk and impact. For example, some argued that the fires were worsened by logging, raising questions about how we manage our forests.

But the new study, published in the journal Nature Ecology and Evolution, found that forest management had little-to-no impact on the severity of the fires. Instead, say the authors, the dominant drivers were topography, severe drought and unprecedented hot, windy weather conditions.

This aligns with previous research demonstrating that climate change has increased the intensity, frequency and severity of fires.

What’s the debate?

  • A new study concludes that native forest logging and past fires had little effect on the severity of the 2019-20 bushfires.
  • Other ecologists disagree with the analysis, arguing that while logging is not the only contributing factor, there is an extensive body of evidence linking logging and fire severity.
  • All agree that climate change is the dominant driver of the increasing frequency and severity of fires.

Study co-author Professor Rodney Keenan, from the University of Melbourne, says: “Some argued that the severity and frequency of these fires were made worse by logging and associated forest management and that harvesting in native forests should cease to reduce fire risk. Little evidence from those fires has been presented to support these contentions.”

Their new analysis, he says, indicates “that the extent and severity of these fires was largely determined by three years of well-below-average rainfall, leading to dry fuels across all vegetation types, extreme fire weather conditions, and local topography”.

The work contradicts a 2020 report by the Australian National University (ANU) and Griffith University, which reviewed 51 papers to examine the relationship between native forest logging and bushfires. While that report found that the primary driver of fire severity is climate, it also found that native logging increases the flammability of forests and therefore raises the chances of high severity fires.

Among the researchers disagreeing with the new paper’s analysis of the effect of native logging is Professor David Lindenmayer, a forest ecologist from ANU who co-authored the 2020 report.

He doesn’t pull punches in his assessment of this new study – he says that it is “a rather unfortunate paper, poorly framed, badly analysed, with the narrative actually not matching the data or the analysis.”

Lindenmayer points out the effects of forest management on the fires’ severity are actually evident in the study’s own data.

“There is an extensive body of science that shows there are strong links between logging and fire severity and the data in this paper actually reinforces exactly that, despite the misleading title of the paper,” he says.

“There are significant statistical problems with the way data were analysed – for example by combining cool fires with crown fires – which greatly weaken the analysis. Despite these problems they still found an effect of logging on fire severity!”

In forests, cooler, lower severity fires are largely confined to the leaf litter and ground cover plants, while the highest severity fires occur when the flames reach the crowns of trees, fully burning or scorching them. These “crown fires” are extremely difficult to control, leading to fast spread and even generating intense storms.

The increasing influence of the climate crisis on bushfire severity is something Australian fire ecologists do agree on.

“There are no quick fixes to the ongoing fire crisis that is afflicting Australia and other flammable landscapes globally,” writes study leader Professor David Bowman, from the University of Tasmania, in an accompanying blog post.

“This crisis is being driven by relentless climate change, which has the terrifying potential to switch forests from critical stores of carbon to volatile carbon sources.”

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