Macarthur's chlamydia-free koala colony is at risk of developing disease due to widespread land-clearing and over-development in the region.
That's the concern of Western Sydney University Stress Lab founder Dr Edward Narayan.
Dr Narayan's new research has found that land clearance is the leading cause of stress in wild koalas living in rural-urban areas - more than bushfires, vehicle collision, dog attacks and disease.
The study is the first scientific evidence of of human-induced environmental change as the number one stress factor on wild koalas.
Dr Narayan said stressed koalas were more susceptible to developing life-threatening conditions.
"The demonstrated long-term stress caused by environmental trauma can lead to significant physical and psychological changes in koalas," he said.
"These changes can result in increased signs of koala stress syndrome; increased risk of infection; suppressed reproduction, growth and development; and high mortality rates."
Dr Narayan conducted his research over several years using faecal samples from 291 koalas.
Koalas found living in areas with land clearance showed significant chronic stress.
This was indicated by high levels of stress hormone cortisol found in the faecal samples.
Dr Narayan said special care was needed to ensure the Macarthur colony continued to thrive.
"It's a no-brainer," he said.
"Koalas living in a fragile landscape, who face losing their homes or access to food and water, will become stressed.
"Animals and humans are alike - no one is immune from stress and its psychological and physical effects.
"Koalas have been here for centuries, they are a part of our core identity as Australians, it would be a shame to see them disappear."
Dr Narayan's research was supported by a grant from the International Fund for Animal Welfare (IFAW).
IFAW regional director Rebecca Keeble said the research indicated that policymakers and developers must factor in the long term welfare of individual animals when planning infrastructure upgrades or new developments.
She said Macarthur's koalas were at a "tipping point".
"Macarthur has a healthy, recovering population of koalas so we need to manage how we can protect them," Ms Keeble said.
"They are a resilient colony, having survived the fur trade of the 1930s.
"But this research shows the long-term effects of development on koalas so we need to ensure that we are doing everything we can to ensure this colony remains disease-free."
Ms Keeble said her organisation would use this research to open discussions with all levels of government.
"Decision makers can no longer look at acceptable death levels or harm to individual animals during the construction phase of a development when green-lighting projects," she said.
"This research proves that the true impact of a development on local koala populations remains well after the bulldozers and construction teams have moved on.
"Koalas must be given more space to live and thrive in if we are going to successfully overcome the challenges posed by urbanisation, human-wildlife conflict and other issues created by human interference."