Nestled beside one of Melbourne’s busiest roads, sits the Bolin Bolin Billabong — a site of immense cultural significance for the traditional owners, the Wurundjeri people.
Part of a once-vast wetland that flowed into the Yarra River, it’s known to them as Birrarung.
It used to be rich in native foods such as waterfowl, fish, eels and plants.
For associate professor in earth sciences and Wiradjuri man Michael Shawn Fletcher, it’s still rich — in priceless data.
His scientific analysis of this muddy waterhole gives an extraordinary window into the past.
A sedimentary storybook
Dr Fletcher is a geographer who studies high-resolution images of fossils, organic material and charcoal trapped in sedimentary layers often deep in the earth.
All of it has been trapped, compressed and preserved over centuries.
To him, it’s like a sedimentary storybook.
“[It is important] to unpack the history of landscape change from Aboriginal management through to the modern day, not only for how we manage this country but understanding how it operates,” Dr Fletcher said.
Varieties of pollen reveal what plants were once present. Charcoal tells the story of fire regimes. Geochemical changes indicate the frequency of floods.
All of it helps reconstruct a picture of the past and chart environmental changes over time.
The long, cylindrical earth samples can sometimes date back thousands of years. Amongst them are stark evidence of dramatic environmental change — and it happened comparatively recently.
“The biggest change that we see most uniformly in the last 10,000 years on this continent is the invasion by the British and a removal of cultural burning from landscapes,” Dr Fletcher said.
A practice disrupted
Dr Fletcher’s’ work may be providing the most compelling data yet about the crucial role of fire in Australia’s ecology.
Cultural burning is the Indigenous people’s practice of skilfully using low-intensity or “cool” fires to manage the landscape.
It removes the fine fuels on the forest floor, such as fallen leaves and twigs, or consumes dry grass to promote new, green growth.
In much of northern Australia, this traditional practice has never stopped. In southern Australia, however, European settlement severely disrupted traditional Indigenous life.
Some colonists, fearful of fire, saw cultural burning as an act of resistance.
The removal of fire from the landscape soon had drastic consequences.
The catastrophic Black Thursday Bushfires in February 1851 burnt 5 million hectares of Victoria.
It was a chilling portent of the nation being periodically scorched by catastrophic bushfires in the years to come.
In his laboratory at the Earth Sciences Building at the University of Melbourne, Dr Fletcher has a core sample from Bolin Bolin that marks the grim event that was the Black Thursday Bushfires.
It is a lump of charcoal the size of a thumbnail that has been dated to about 1850.
Learning from the past
Dr Fletcher’s findings are profoundly important for understanding the past. Crucially, they point to how we approach the future.
“We see a shift from an open-forest system to a closed-forest system in all the examples that we’ve analysed,” he said.
“Universally, across landscapes that [are] not now farms, we see open forests turning into closed forests.
“In terms of fire, that’s a ramping up of fuel levels.
The study of pollens and other organic matter from earth samples also indicates a loss of plant biodiversity.
Many less flammable species have disappeared, replaced by highly combustible eucalypts.
Dr Fletcher believes the loss of cool, mosaic burning since European settlement has left us, as a nation, dangerously fire prone.
“It has created a situation where we have connected incredibly flammable overstocked forests that go for hundreds, if not thousands, of kilometres across the south-east Australian seaboard,” he said.
Experts say radical change needed
This groundbreaking work has some sizeable support, including from prominent Indigenous leader and academic Marcia Langton, who is also a geographer and anthropologist.
Professor Langton has been a long-time advocate of restoring Indigenous people’s burning practices across the continent.
She believes that if we are to avoid catastrophic wildfires such as the Black Saturday and Black Summer events, we need radical changes to fire prevention and management.
“Take a commonsense view, adapting to the Aboriginal way of managing country, using science and coming to grips with this Australian landscape and its ecologies, and not importing European ideas here which frankly have been disastrous for the country,” she said.
There are now some 850 Indigenous ranger groups across Australia, nearly all of which use cultural burning as part of their environmental management.
With predictions that a warming climate will see more extreme fire events, Dr Fletcher’s scientific work is attracting global attention.
Professor Langton agreed.
“I think we’re at a critical point in Australia’s history,” she said.
Watch this story on ABC TV’s Landline this on iview.