SYDNEY, May 27 (Xinhua) -- Even moderate temperature rises can increase hospital admission and mortality risk in endangered koalas, new research reveals, highlighting growing threats from climate change.
An Australian study led by the University of Sydney analyzed hospital admission records of nearly 12,000 koalas in the state of New South Wales (NSW) over two decades and found that admission and mortality rates rose once average temperatures exceeded 27 degrees Celsius, said a media release from the university on Wednesday.
Exposure to temperatures above 30 degrees Celsius increased the likelihood of hospitalization or death by 1.5 to 3.5 times compared to 25 degrees, according to the findings, highlighting the need to mitigate heat-related threats for wildlife as the climate continues to warm.
The impact was most severe in inland northwest NSW, where rising temperatures and drought have already contributed to sharp population declines. The koala population in Gunnedah, once known as the "koala capital of the world," is now considered "functionally extinct," said Valentina Mella from the Sydney School of Veterinary Sciences under the University of Sydney.
Published in Biology Letters, the study provides the first evidence linking heat stress to koala mortality. Tree-dwelling species like koalas are especially vulnerable due to limited heat tolerance and restricted foraging range.
Previous evidence relied on observational data, which is less robust and more anecdotal and individualized, Mella said. Researchers also found that disease, particularly chlamydiosis, and habitat loss intensified vulnerability to heat.
"Koalas can handle hot weather in the short-term, but their coping mechanisms aren't sustainable in the long term," said Mella, adding that without intervention, rising extreme heat could "push already vulnerable koala populations closer to extinction." ■
