Australian forestry does not make forests more flamable

The views of Australian academics Professor David Lindenmayer and Associate Professor Philip Zylstra, as reproduced in recent CFA Newsletters (December 2023 and March 2024), that logging and prescribed burning are making Australian native forests more flammable are highly contested by many Australian forest scientists and fire management practitioners. These academic scientists advocate that timber harvesting in native forests should cease, prescribed burning should be confined to areas close to high value assets and that when fire is excluded for more than 40 years the native forests do not burn at high intensity, because the vertical connectivity of the forest structure is reduced through natural ecological processes.

These propositions ignore the evidence from decades of comprehensive fire research undertaken by Australia’s peak scientific organization (CSIRO) and the State government forest land management agencies, as well as the lessons from numerous inquiries following major wildfires over the past 80 years. They are also inconsistent with the lived experience with forest fire in many parts of Australia in recent decades. Moreover, the notion that fire can be excluded from most Australian forests for more than 40 years is fanciful, given the increased frequency and extent of wildfires over the past 20 years under changing climatic conditions. Importantly, there are numerous journal articles that either challenge their research findings or present evidence that indicates their findings are incorrect (see for example Attiwill et al. (2014), Hislop et al. (2020), Keenan et al. (2021), Bowman  et al. (2021) and Miller et al. (2024).

Wildfires occur in Australian forests almost every year, with the number of major wildfires and the area burnt increasing in years when there is above average fire danger, which usually corresponds with periods of prolonged drought. However, due to well managed fire suppression arrangements, only a small proportion of wildfires are unable to be extinguished while small and then burn at high severity and cause most of the impacts on life, property and the environment. Wildfire behaviour, including both the rate of spread and the intensity at which a fire burns, is dependent on three main factors: the quantity and structure of available fuel in the vegetation; the prevailing weather (particularly temperature, wind and humidity); and the topography at the location of the fire. Therefore, the severity of a wildfire at any point in the landscape is a result of many interacting factors, not a single factor such as whether or not timber harvesting has been undertaken in that location.

Professor Lindenmayer’s claim that timber harvesting makes forests more flammable arises from research published in 2014, that examined fire severity outcomes in different aged Eucalyptus regnans forests that were burnt in the catastrophic 2009 Victorian Black Saturday wildfires. The researchers analysed post-fire remotely sensed fire severity data, focusing on two categories of high severity fire: canopy consumption, where 70-100% of tree canopies were burnt; and canopy scorch, where 60-100% of the canopies showed scorched leaves. From their analysis, they claimed that there was a 70% chance of 15-year-old stands being burnt at high severity with total canopy consumption and that canopy consumption rarely occurred in old growth stands aged around 300 years. From this they concluded that the stands regenerated following logging had made those forests more flammable.

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Source & image credit: Forestry Australia