Research into frequent prescribed burning in a globally important hotspot in southwestern Western Australia reveals a negative impact on endangered species.

We are constantly reminded by government agencies that the bush must be burned to avoid being incinerated in our beds. This has been made more urgent due to fires becoming more fierce and more frequent as a result of global warming. But we are not told of the havoc to wildlife caused by too frequent burning, nor of the desecration of ecosystems that rarely experienced severe fire before the arrival of Europeans. We are also not told that recent research shows frequent prescribed burning maintains the forests in a highly flammable state for up to 20 years.

A recent publication in the Australian Journal of Zoology by seven of Australia’s top biologists is highly critical of Western Australia’s Department of Biodiversity, Conservation and Attractions (DBCA), which is charged with protecting and conserving the state’s unique southwest global biodiversity hotspot. The paper was sparked by a comment from the state’s then Premier, Mark McGowan, stating he had been informed by DBCA staff that a prescribed burn in 2021 had not killed any endangered numbats. This conflicted with DBCA’s statement that they “carry out no population studies of numbats either before or after fire”.

In the paper, the authors provide examples of species and ecosystems affected by the prescribed burning policy, adopted after the Ferguson Report on the 2016 Waroona fire, in which “a fuel age of less than six years will be maintained across 45 per cent of the landscape on State Forest, National Parks and other Parks and Wildlife managed lands in the South West and Perth Hills”.

This policy has to be set against the knowledge that the fire frequency in the jarrah forests of Western Australia prior to European colonisation was 81 years, falling to 17 years after a decade of burning and clearing by settlers.

What actually happens to these ancient ecosystems when they are now being burnt every six years?

We know from a long-term study of the honey possum, a 9 g marsupial nectarivore found only in the southwest of WA, that two fires six years apart will take the population 25.6 years to recover to pre-burn densities. Research on mainland quokkas in the northern jarrah forest has also shown that they avoid frequently burnt areas and prefer long-unburnt habitats. The critically endangered western ringtail possum is also at risk. A “cool” burn of a small nature reserve, Warrangup Springs, near the town of Mandurah in May 2018 resulted in the death of 17 of 22 possums being monitored by a volunteer citizen scientist.

The burning of peat swamps in recent years has had a disastrous impact on the rare carnivorous Albany pitcher plant (Cephalotus follicularis) with many swamps smouldering for up to a year after the fire.

The most egregious example of the impact of prescribed burning has been in the ancient Tingle forests north of Walpole in southwest WA. These trees, which can be up to 400 years old, are hollowed out by fires burning at the base of the tree, leading to their collapse. After one fire in December 2024, an independent count found 178 collapsed trees (2.1 collapsed trees per hectare) for the 85 ha area after the fire.

The impact of prescribed burns is also serious for conservation-listed species of cockatoos: the critically endangered Carnaby’s cockatoo (Zanda latirostris); the endangered Baudin’s cockatoo (Zanda baudinii) and the forest red-tailed black cockatoo (Calyptorhynchus banksii), each of which depends on forest and woodland for forage, roosting and nest hollows in old trees.

Key burning periods for southwest Western Australia coincide with peak nesting periods for most bird species. Impacts are particularly profound for the red-tailed cockatoos, which are unique in having two nesting periods, in autumn and spring, both coinciding with large-scale prescribed burning periods. Fire impacts on cockatoos observed following prescribed burning include loss of forage species, suffocation in hollows and tree collapse. Tree collapse is up to three times greater following prescribed burning than from wildfire, due to the longer residency time following the low wind and moist litter conditions favoured for prescribed burns.

Carnaby’s and Baudin’s cockatoos are declining across the region due to land clearing and inappropriate fire regimes. Recent research shows that with 60 per cent of areas having a fuel age of seven years or less under current burning regimes, landscapes will support less than a third of the cockatoo populations compared with unburnt areas.

The research paper concludes that “DBCA’s current burning program is likely to have a negative impact on a range of species that rely on long-unburnt habitats for their survival. Despite this, DBCA currently conducts no rigorous monitoring of the effects of its prescribed burning program on biodiversity, eschewing any surveys before and following burns. Thus, DBCA avoids its remit to conserve biodiversity and natural values in the forests and bushland it manages. In addition, DBCA currently has no policy on the retention of extensive areas of long-unburnt habitat, which are pivotal for the survival of several iconic species.”

The views expressed in this article may or may not reflect those of Pearls and Irritations.