When a 5,500-kilometre dingo fence was constructed between Queensland and Western Australia in the late 1800s and early 1900s, the idea was to stop dingoes from killing livestock in the pastureland to the south.
But by excluding an apex predator, scientists believe we may have triggered a “trophic cascade” that has changed the physical shape of the landscape.
In research published in the Journal of the Royal Society Interface this week, scientists say the shape of sand dunes on the inside and the outside of the fence is markedly different.
Spinifex-hopping mouse numbers have been affected by feral cats and foxes.
Supplied: Matthew Brun
Trophic cascades occur when a top-order predator is removed from an ecosystem, resulting in a series of actions that end up remodelling the system as a whole.
In this case, dingo numbers on the inside of the fence have been supressed by state-sponsored culling programs that continue today.
This has led to a boom in feral cat and red fox populations, which in turn has decimated the numbers of many of the small rodent and marsupial species of the desert region.
And part of the diet of these small, omnivorous species includes the seeds and seedlings of the low desert shrubs that grow in arid regions of the study area, according to lead author Dr Mitchell Lyons from the University of New South Wales (UNSW).
Trophic cascades likely to have happened across Australia
Researchers say there are significant differences in the dunes on either side of the fence.
Supplied: Mitchell Lyons
In essence, the researchers believe that by removing small omnivorous animals like the spinifex-hopping mouse, shrubs have been able to grow in much greater abundance.
More shrubs have led to more shade, which allows heat-sensitive plant species, as well as lichens and mosses to survive in the low undergrowth.
This increased vegetation has heightened the structural integrity of the dunes, and altered the way the wind flows and shifts sand across the landscape.
The result, according to the researchers, is higher and more varied dunes on the side of the fence where dingoes are excluded.
And similar trophic cascades may have occurred over other regions of Australia where dingo numbers have been kept low by culling, Dr Lyons said.
While it is generally accepted that dingoes play a defining role in shaping the ecology of their habitat, there are some who still believe their influence may have been overstated.
A paper published in Food Webs last year claimed that research into dingoes (and wolves) often drew sweeping conclusions from limited data, and that the animals may not be as responsible for trophic cascades as some research claims to show.
But because the 5,531-kilometre fence presents such a stark demarcation between dingo habitat and not, it’s the perfect region to study the effect of the animal on the environment.
Lessons for Australia in Yellowstone rewilding
Associate Professor Euan Ritchie from Deakin University, who wasn’t involved in the current study, is one of a group of researchers who have suggested a novel way of using the fence to test the hypothesis.
“What we wanted to do was to test the idea that dingoes were having a regulating role within the system,” he said.
Because reintroducing dingoes to farmland in so politicised, he said moving part of the fence that runs through Sturt National Park in western New South Wales would allow researchers to conduct the study without affecting graziers.
Reintroducing keystone species from areas where they have been wiped out is known as rewilding, and it’s gaining traction around the world as a way of restoring ecosystem structure, according to Dr Ritchie.
Yellowstone National Park in Wyoming in the United States is often cited as one of rewilding’s great success stories, and is a textbook example of a trophic cascade.
Dr Lyons said his research into dingoes partly evolved from the Yellowstone model.
“That was kind of at the back of my mind, one of my motivators. I remember reading [about Yellowstone] almost a decade ago now,” he said.
In 1995, wolves were returned to Yellowstone National Park following a 70-year absence.
In their absence, deer populations had exploded out of control, overgrazing on tree saplings and expanding areas of grassland.
After wolves were reintroduced to the park, not only did deer numbers fall, but a series of follow-on effects ensued.
More trees grew and forests expanded, which brought in birds. Tree density on the rivers increased and stabilised the riverbanks, changing the water flow. In turn, more trees meant more beavers, and the ecological niches created by beaver dams attracted things like otters and ducks.
The wolves also kept coyote numbers down, allowing mice and rabbit numbers to grow, and predators like weasels and badgers also flourished.
Although it’s unlikely that reintroducing dingoes would have an effect of such magnitude on Australian ecosystems, Dr Ritchie said it’s a prospect that needs more attention.
“Bringing back species, not just dingoes, but species that have really important ecological roles…especially with Australia’s [poor] record on conservation, that’s something we need to be looking at more,” he said.