Colonial land-use change may have helped fuel Australia's current wildfire crisis, according to a new study from environmental researchers in the UK and Australia.
Co-authored by the University of Nottingham's Dr Michaela Mariani in the School of Geography, and led by experts at the University of Melbourne, the research published in Nature, reveals how the disruption of Indigenous fire management transformed southeastern Australia's landscape and increased its vulnerability to intense wildfires.
The global wildfire crisis is often attributed primarily to climate change. However, these new findings highlight how historical changes to land management can also shape the landscapes in which wildfires occur. Before British colonisation, the Indigenous Gunaikurnai people of southeastern Australia used frequent, low-temperature cultural burning to maintain an open woodland ecosystem and reduce the build-up of flammable vegetation.
Climate change is undoubtedly increasing wildfire risk, but our study shows that climate is only part of the story. The landscapes that burn today are also the product of decisions about how land has been managed over centuries."
"Our results show that removing Indigenous fire management fundamentally changed the structure of this landscape. More trees meant more fuel, and more fuel created the conditions for hotter and more intense fires."
The team of researchers reconstructed 1,000 years of vegetation and fire history in southeastern Australia, finding that the landscape remained remarkably stable as open woodland for more than 800 years under Gunaikurnai management.
Following the disruption of Indigenous fire management after British colonisation in the 19th century, eucalypt cover increased fourfold, from around 9 per cent to 34 per cent, transforming the landscape from open woodland into forest. Fire temperatures also increased, while soil erosion accelerated.
To reconstruct the region's long-term vegetation and fire history, the researchers extracted and analysed a one-metre sediment core from the deepest part of Purghagoolah (Lake Elusive) in southeastern Australia.
By analysing ancient pollen, charcoal and sediment layers, they were able to reconstruct changes in vegetation, fire activity and the landscape over the past 1,000 years.
Importantly, the researchers found that these changes occurred before significant human-driven climate change emerged around the 1950s. This suggests that colonial land-use change created a long-term legacy that has increased the vulnerability of southeastern Australia's eucalypt forests to wildfire, while also amplifying the influence of climate change.
Dr Mariani, added: "This study demonstrates the value of looking deep into the past. A thousand-year record allows us to distinguish recent climate effects from much older changes in land management and shows how decisions made nearly two centuries ago continue to influence the fires we experience today."
The study identifies a reinforcing feedback loop, described by the researchers as a 'catastrophic wildfire loop'. Infrequent, intense fires can increase the amount of flammable vegetation that grows after a fire, creating conditions for increasingly severe fires in the future. This can make landscapes already altered by colonial land management particularly vulnerable to the additional pressures of a changing climate.
Highly flammable eucalypt forests now cover much of southeastern Australia. The scale and lasting impact of the 2019–2020 Black Summer fires, which burned more than 24 million hectares, demonstrate the devastating consequences of large wildfires in the region.
The researchers say the findings highlight the importance of recognising historical land-use change when assessing contemporary wildfire risk. They also suggest that Indigenous knowledge and cultural burning practices could play an important role in restoring ecological resilience and informing future fire management strategies.
