Scientists say Australia's iconic koala bear is at risk of extinction due to stress on its immune systems caused by bushfires and habitat destruction.
Aussie researchers have analysed 29 years of data from three koala hotspots in New South Wales, the country's eastern state.
Koala populations have steadily declined mostly due to disease – the most common reason that they're admitted into care – with chlamydia being the most common condition, they found.
But bushfires and destruction of their habitat by humans – to create new building developments, for example – have made koalas more susceptible to disease by stressing their immune systems.
The koala (Phascolarctos cinereus) is currently listed by both the IUCN and Australia's Threatened Species Scientific Committee as vulnerable to extinction with an overall decreasing population trend
Stress from these events triggers the production of a class of hormones called glucocorticoids, they say.
'Any disturbance to an animals habitat activates the physiological stress response, and if said stressors do not cease, the excessive production of glucocorticoids can leave the animal with a compromised immune system and therefore likely to contract a disease,' say the experts from Western Sydney University at the University of Queensland.
'There is an urgent need to strengthen on-ground management, bushfire control regimes, environmental planning and governmental policy actions that should hopefully reduce the proximate environmental stressors.
'This will ensure that in the next decade, beyond 2020, NSW koalas will hopefully start to show reversed trends and patterns in exposure to environmental trauma and disease, and population numbers will return towards recovery.'
Bushfires and habitat destruction caused by human activities, such as land clearing for building developments, have ultimately contributed to the decline of the koala all over Australia, they say.
In Australia's metropolitan areas, meanwhile, dog attacks and vehicles are threats for the distinctive eucalyptus-eating species.
A firefighter giving a koala water during the summer bushfires. This photo was shared by Dr Chris Brown, a popular Australian veterinarian and TV personality in January 2020, who said offering a koala a drink from a bottle isn’t without risks, as water forced down their throats can easily end up in their lungs
Koalas are listed as 'vulnerable to extinction' by both the International Union for the Conservation of Nature (IUCN) and the Australian government's Threatened Species Scientific Committee.
However, the species could be soon be officially uplisted from its current status of 'vulnerable' to 'endangered'.
To better understand these long-term patterns, researchers analysed data from three wildlife rescue groups in New South Wales – Port Stephens Koalas, Port Macquarie Koala Hospital and Friends of the Koala based in Lismore.
The data covered 1989 to 2018 and included 12,543 records of wild, rescued koalas, admitted to care in one of the three locations.
Researchers analysed close to three decades of data from Port Stephens, Port Macquarie and Lismore - major koala hotspots in New South Wales
A young female koala fondly named 'Ash' is seen sitting on a Eucalyptus branch following a general health check at the Australian Reptile Park on August 27, 2020 on the Central Coast in Sydney, Australia
Analysis revealed that the most common reason a koala was recorded as a sighting or admitted for clinical care was disease – most often with signs of chlamydia.
Most koalas that were sighted or admitted for clinical care looked at in the study –29.74 per cent – were released back into the wild.
'This study indicates that, between all three rescue sites, koalas are most often rescued due to signs of chlamydia, and the outcomes of the treatment were often favorable – with most koalas released back into the natural environment following treatment,' said study author Dr Edward Narayan at the University of Queensland.
However, 17.44 per cent of the koalas in the study sample had to be euthanised.
Incidence of disease and euthanasia were generally