Rolf Schlagloth, CQUniversity Australia; Charley Geddes, CSIRO; Douglas Kerlin, Griffith University, and Flavia Santamaria, CQUniversity Australia
Warning: this article contains graphic images some readers may find distressing
The beloved koala is now endangered in New South Wales, Queensland and the Australian Capital Territory. The tree-dwelling marsupial is threatened by land clearing, loss of its favourite eucalypts, chlamydia, being preyed on by feral animals and – last but not least – collisions with vehicles.
To arrest the steady decline of koala populations, we must focus on where these animals are being wiped out in front of our eyes.
In Central Queensland, there’s a known koala death hotspot. The Peak Downs Highway connects Mackay on the coast with the Bowen Basin coal mining region. Cars and trucks travel along the highway at speed. The road is notoriously dangerous for humans, with a death toll in the dozens. But it’s also lethal for koalas.
How many are killed? Throughout 2023, citizen scientist and honours student Charley Geddes and our team of scientists counted 145 otherwise healthy koalas struck and killed along a 51 kilometre stretch of this highway. This is a huge figure. By contrast, an average of 365 koalas are admitted to veterinary hospitals each year after being hit by a vehicle across the entire south-east Queensland region.
A roadkill hotspot is a problem that can be solved. In other areas, state and territory governments have built overpasses or underpasses, usually alongside wildlife exclusion fencing to guide the animals to safe passage. In some instances, rope bridges have been installed high above highways.
Unfortunately, there’s very little funding to tackle roadkill hotspots in Central Queensland. Koala conservation efforts by the state government have, to date, focused almost exclusively on south-east Queensland. Our horrifying data shows that must change.
Pity the Central Queensland koala
In Queensland, modelling suggests land clearing and climatic change will gradually drive koalas from the drier west to the wetter east, near the coast.
Koalas are holding out in wetter, more intact refuges such as the Clarke-Connors Range, a coastal mountain range inland from Mackay. These mountains are now home to a significant koala population and, potentially, one of national importance.
Unfortunately, this koala haven has one major problem: fast-moving vehicles. The Peak Downs highway runs directly through this prime koala habitat.
When koalas go roaming for food or to find a mate, they often cross the highway. These exploring koalas are typically male.
What makes this stretch of highway particularly lethal for koalas is the fact the habitat is in good condition. Good land management by some local graziers has meant many eucalypts have been conserved, benefiting koalas and other wildlife. This has been done deliberately, as these trees provide shade for grazing animals. The gum trees koalas prefer – blue gums and ironbarks – are found all along the highway. As a result, we found koalas were being killed nearly anywhere along the stretch.
As yet, we don’t have a good idea about how many koalas are living in the area. More work needs to be done to get good estimates. But the population must be considerable, due to the numbers dying on the roads.
Fences and underpasses
In urban areas, small patches of koala habitat exist alongside houses, industrial parks, commercial centres, roads and parkland. So koalas tend to be concentrated in small patches. In turn, this means it’s actually easier to help them cross roads – you can direct them to a safe crossing point.
It’s much harder to safeguard koalas along a 51 km stretch of highway, with lots of good quality habitat all along the roadside.
On the plus side, the fact there are fewer private properties (mainly used for grazing cattle) would likely make it easier to negotiate to install road barriers or underpasses and overpasses.
Better still, there is some appetite for change. Many landholders in the area are on record expressing their concern about how many koalas are dying on the highway.
As one landholder told us:
All the local landholders that I know in the area seem to be quite proud and empathetic towards koalas. They are creatures that do not impact grazing operations in any way and are treasured for want of a better term.
Several said the solution was fencing. As one said:
Wildlife fencing is the only way to stop the absolute carnage of these wonderful creatures.
A number of landholders have expressed willingness to host fencing on their land.
In recent years, state road authorities have retrofitted several highway underpasses in an attempt to guide koalas to a safer route under the road. Unfortunately, these efforts have not worked.
Previous studies have shown wildlife exclusion fencing can work, but this has been tested only on a local scale. For the Peak Downs Highway, a much greater length of wildlife fencing would likely be needed to actually direct the koalas to safe passage.
The indirect toll from mining
One major reason why so many koalas die on this stretch of highway is because of the high volume of traffic, much of which is going to and from the coal mines in the Bowen Basin. This geological basin contains Australia’s largest body of coal, and has 48 active coal mines as of 2023. Queensland’s largest export is still metallurgical coal.
The high death toll is clearly an indirect consequence of mining operations.
As koala populations shrink in many areas, wetter mountains in Central Queensland have become a vital refuge. But even here, Australia’s iconic tree-dweller is under threat. Many koalas here have diseases such as chlamydia and koala retrovirus, and specialist care for injured or sick animals is harder to come by in this region.
Authorities have moved to tackle the koala road toll in some regions. But the koalas of Central Queensland have largely missed out. As the iconic species reels from a multitude of threats, making this dangerous highway safer to cross offers one way to stop more koalas from dying, week in, week out.
Rolf Schlagloth, Koala Ecologist, CQUniversity Australia; Charley Geddes, Research technician, CSIRO; Douglas Kerlin, Postdoctoral Research Fellow, Environmental Futures Research Institute, Griffith University, and Flavia Santamaria, Lecturer in Biology, CQUniversity Australia
This article is republished from The Conversation under a Creative Commons license. Read the original article.
