Climate change is amplifying the impact of disease in NSW’s vulnerable koalas and local extinctions will likely be the result, a leading veterinarian warns.
Worsening heatwaves have severely impacted the marsupials across the state’s northwest, with each event leading to population declines of between 20 and 25 per in some areas.
While healthy koala populations would simply breed up their numbers again, most populations in NSW are affected by chlamydia, a disease which results in blindness, infection and infertility.
They face a perfect storm of illness and extreme weather which has researchers fearing for their future.
University of Sydney’s Professor of Veterinary Pathology Mark Krockenberger believes between 80 and 90 per cent of koalas in the Gunnedah region suffer from chlamydia, meaning that the majority of females are unable to reproduce.
“The population is getting older and older and as they die, they're not being replaced,” he told Yahoo News.
“So populations are in quite a risky position in terms of local extinctions.”
Numbers plummet in 'koala capital of the world'
Driving into Gunnedah, motorists are warned to 'slow down' because of koalas, but these days trucks and utes servicing the region's many coal mines are a more common sight than wildlife.
Once dubbed the 'koala capital of the world', populations in the town have been directly impacted as rivers dried up and trees died.
The Australian Koala Foundation (AKF) estimate the electorate of Parkes, where Gunnedah is situated, had between 2100 and 2500 koalas in 2018, but now there are between 500 and 750.
The charity’s founder Deborah Talbert witnessed the worsening impacts of climate change in 2014, when the weather soared above 40 degrees in parts the region for extended periods.
Volunteer carers contacted her saying they were seeing animals stream in suffering the effects of dehydration and starvation.
“How can the koalas survive this, they've got nothing to eat?” Ms Talbert said.
“It’s all habitat related and with the chlamydia, koalas are like us, if you haven’t got anything to eat, you get sick.”
Increased emissions turns gum leaves toxic
In the Pilliga, west of Gunnedah, it was common to see koalas in the 1990s, however it is rare to see the animals in this region today.
Concern about Gunnedah's koalas has reached the federal level, with the government promising $1 million in funding today to help protect them from drought and the changing climate.
The combination of disease and climate-change augmented weather has led Professor Krockenberger to hold “grave fears for koala populations” in NSW, particularly in the western part of their range.
Although there is some degree of breeding continuing to occur, he thinks numbers in Gunnedah will decline “pretty dramatically" over the next five years.
Research has demonstrated that on top of drought, increased carbon dioxide in the atmosphere is resulting in increased toxins in eucalyptus leaves, the koala's only food source.
This change in chemical composition is believed to be affecting the function of koala immune cells, adding yet another stressor contributing to decreased resilience to resist disease.
Hope remains despite 'pretty big problem' koalas face
Despite the pressure on koalas, Professor Krockenberger remains optimistic.
Researchers are seeing some positive signs with chlamydia immunisation trials, and a new form of the vaccine is undergoing a field trial to see if it is more effective.
They hope to reduce transmission of the disease from affected to unaffected koalas, so healthy animals are able to breed and repopulate.
“I'm hopeful that vaccination will play a part of the solution,” he said.
“(Chlamydia is) just a pretty big problem at the moment.”
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