Koalas are facing extinction after decades of bushfires, habitat loss and damaging human activity, research has shown.
Koalas are currently listed as "vulnerable" in Australia, but the Government is under pressure to give them an emergency classification as an endangered species.
Now a 29-year study of the koala population in New South Wales, home to 10 per cent of the country's koala population, has identified the key causes of their decline.
It found that they could be more susceptible to chlamydia, the most common disease among the marsupials, and other illness because of the stress of habitat loss as a result of agriculture, bushfires and human encroachment.
Between 2010 to 2014, nearly 300,000ha of land rich in native eucalypt species, a favourite of the koala, was cleared in New South Wales alone.
The study also pointed to the growing number of bushfires as a major threat to koala populations, either through directly killing or injuring the animals, or by destroying their habitats.
Unprecedented bushfires that tore through Australia in late 2019 are believed to have had a catastrophic impact on koala populations, killing up to 30,000, according to one estimate.
Bushfire conditions are forecast to occur four times as often if global temperatures rise by 2C, as is already forecast.
It is unknown how many koalas still exist in the wild, but estimates range from 80,000 to 300,000.
Marsupials, including koalas, have suffered the greatest population loss of any species since colonisation in Australia, which has the world's highest rate of mammal extinction.
Since 1788, 30 local mammal species have become extinct, with 55 others seeing their conservation status threatened.
The study found koalas were also falling victim to vehicle collisions and dog attacks as human residential areas encroach into their natural habitat.
"Australia's national wildlife icon, the koala currently faces the brink of extinction crisis due to environmental trauma and diseases," the authors said.