Forest expansion and thickening after British colonisation has created landscapes more prone to burning, amplifying the influence of climate change and propelling Australia’s bushfire crisis, a new study finds.
ANSTO has supported research published yesterday in Nature by University of Melbourne researchers, in collaboration with Gunaikurnai Land and Waters Corporation, that reconstructed the past 1000 years of vegetation, fire and erosion in Croajingolong National Park in East Gippsland, one of southeastern Australia's most fire-prone forests.
The researchers found that colonialisation drove cascading changes: increased fire temperature, a four-fold increase in eucalypt cover, transformation from an open woodland to forest, and increased soil erosion.
Lead author, University of Melbourne Professor Michael-Shawn Fletcher, said the research provides scientific evidence for the value of cultural burning and the need to integrate Indigenous knowledge into contemporary fire management strategies.
“When Country is cared for, climate does not dictate wildfire,” Professor Fletcher said.
“For thousands of years, Gunaikurnai people cared for Country in what is now Croajingolong National Park through cultural burning, keeping much of the landscape as open woodland.
“Climate records show that seasons of comparably dangerous fire weather, such as those seen during Ash Wednesday and Black Saturday, reoccurred in the region repeatedly before colonisation, yet the open landscape maintained by cultural burning protected the land from catastrophic fire.
“When colonisation ended that care, the forest expanded and thickened across the region, loading the landscape with fuel. It is that transformation that has handed control of fire to climate.”
The research found the transformations to the land predate human-driven climate change, demonstrating the current vulnerability of southeastern Australian eucalypt forests to wildfire is strongly influenced by colonial land-use legacies.
“Most discussion of Australia's wildfire crisis stops at climate change. Our work shows what set the stage for it – forest expansion and thickening that loaded the landscape long before the climate began to shift,” said Professor Fletcher, from the School or Geography, Earth and Atmospheric Sciences.
Reading the lake sediment record, researchers found the hot fires came first, driving a four-fold surge in eucalypts that thickened the once-open woodland into forest and loaded the landscape with fuel. Infrared analysis of charcoal preserved in the sediments reveals past fire temperatures, showing the cool cultural fires of the pre-colonial period being replaced by hot wildfires after colonisation.
Patricia Gadd, Science Program Leader for Food and Water in the Environment Research and Technology Group at ANSTO and a Principal Investigator in the ARC Centre of Excellence for Indigenous and Environmental Histories and Futures (CIEHF), a co-author, applied X-ray fluorescence core-scanning (ITRAX) to support the research. It was used to generate high-resolution geochemical records from sediment cores, providing critical evidence of long-term environmental change, vegetation dynamics and fire history across the study site.
The data helped the research team reconstruct how land management practices and ecosystem conditions changed over the past millennium, contributing to a deeper understanding of the links between colonial land-use change and contemporary wildfire risk.
“The sediment record provides a remarkable window into how people have shaped Australian landscapes over centuries, Using ANSTO’s Itrax technology, we helped reconstruct environmental changes that reveal the lasting impact of disrupted cultural burning on today's wildfire risk. This research demonstrates the importance of integrating Indigenous knowledge and science to support future land management,” said Ms Gadd.
The paper concludes that restoring cultural burning and supporting Traditional Owners to care for Country is an essential component to mitigating wildfire risk.
GunaiKurnai elder Uncle Russell Mullet from Gunaikurnai Land and Waters Corporation, said Gunaikurnai Ancestors were born with towera (fire), an interrelationship of the Old Peoples practical daily life on country.
“Not treating country with towera, country becomes extremely dangerous for GunaiKurnai, animals and plants,” Mr Mullet said.
“Studies such as this provide firm scientific evidence to support towera land management initiatives for country.”
The study also addresses a larger cultural point on the concept of wilderness – a powerful cultural and environmental idea describing land largely untouched by humans.
“Croajingolong National Park has long been treated as pristine wilderness, yet it is now one of the most fire-prone and repeatedly burnt parts of southeastern Australia,” Professor Fletcher said.
“The forest we protect there is in fact a product of colonisation, and it’s that legacy that now imperils its very survival.”
Read more on the Conversation.
Information for this article came from the University of Melbourne media release
