When bushfires burn through the spinifex plains on Ethabuka and Pilungah reserves, arid species find refuge in Gidgee woodlands that are as vital to their survival as they are threatened.
When Glenda Wardle first stepped onto the red sands of Ethabuka Reserve, Wangkamadla country, in 1998, she had no idea of the scientific journey she was embarking upon.
“Back on that very first trip, my initial impression was awe at the amount of plant life in Australian deserts – it’s not just grasslands, there are lots of shrubs,” she says.
“Our idea of deserts being stark, barren places is a little different to the reality in Australia.”
Gidgee Woodlands sit in the swales between sand dunes. Photo by Wayne Lawler.
Glenda and her colleague Chris Dickman lead the University of Sydney’s Desert Ecology Research Group, which has been studying Bush Heritage’s Ethabuka and Pilungah (formerly Cravens Peak) reserves for over 30 years. Their dataset represents one of the longest-running studies of any arid system in the world.
At the heart of Glenda’s research are two ecosystems that have an intriguing relationship to one another: Georgina Gidgee Woodlands and Spinifex Grasslands. The former is dominated by the gnarled forms of slow-growing Gidgee trees (Acacia georginae), and the latter by the spikey, circular mounds of the hummock grass, Triodia basedowii, also known as spinifex.
In isolation, these ecosystems each support many species: Spinifex Grasslands provide food and shelter for a huge diversity of reptiles, small mammals and seed-eating birds, while the woodlands provide habitat for over 80 bird species. But when the woodlands occur alongside the grasslands, as they do on Ethabuka and Pilungah reserves, they take on a whole new role.
Gidgee Woodlands are usually found in lower swale areas between dunes and are generally quite resilient to fire. As a result, they become safe havens for desert animals fleeing grassfires and the mouths of the hungry predators that are attracted by the smoke.
“After flooding rain, the grass grows rapidly then dries out and we anticipate fires that burn the spinifex and create a riskier environment for fauna,” says Glenda. “When that happens, we noticed that the Gidgee Woodlands next door provided shelter and food resources and acted as a refuge for fauna and plants.”
Worryingly though, the future of Gidgee Woodlands is uncertain.
University of Sydney Desert Ecology Research group at Pilungah. Photo Krystle Wright.
Earlier this year, a research paper co-authored by Glenda and published in Global Change Biology identified the woodlands as one of 19 Australian ecosystems on the verge of collapse.
The causes are so numerous as to be overwhelming: over-grazing, weeds, feral animals, the historic harvesting of Gidgee wood for fence posts, and, increasingly, climate change.
Without intervention, the woodlands are at risk of desertification, which could have severe consequences for biodiversity. Without them, the fear is that arid animals will have nowhere to go when the desert burns.
For Wangkamadla Traditional Owner Avelina Tarrago, the potential loss is twofold, encompassing both conservation and culture.
“My old people traversed that country, using the Gidgee wood to make shelter and for ceremony – proud cultural practises which we continue today,” she says. “The recent report was a stark warning… and one that cuts me to my core as I think about my deep connection to my country.”
Wangkamadla Traditional Owner Avelina Tarrago. Photo Peter Wallis.
Aside from taking urgent action to curb the impacts of climate change, Glenda says that alleviating pressure from grazing, controlling feral animals such as camels which graze on Gidgee foliage, and managing Buffel Grass, which fuels hotter fires, will all help safeguard Gidgee trees.
It’s now 23 years since Glenda first set foot on the red sands of Ethabuka, and 17 years since Bush Heritage purchased the former pastoral station. Her data captures the story of a landscape in recovery, having now been destocked and protected.
“We're starting to really get to see the outcomes of that change management,” says Glenda. “With the de-stocking, we've been able to observe a great recovery in the vegetation, particularly in the regrowth of Gidgee branches and foliage near the ground.”
More vegetation is of course good news for native wildlife, too, providing food, nesting habitat and shelter from predation.
“After 30 years of monitoring, there are still new discoveries but nothing has been lost in these reserves, which is not a small thing to say given all the threats wildlife are facing.”