(CNN)It has been a stressful year for Australia's koalas. Their health and natural environment, however, have been under threat for a long time.
Bushfires, habitat fragmentation, vehicle collisions and dog attacks -- all which hurt koalas -- have been getting worse over the last decade.
That has led to species population decline and increased disease among koalas, according to new research published Wednesday in the academic journal PLOS ONE.
The number of diseased koalas increased over the course of 30 years, while the number of sick koalas that could be released back into the wild dropped, the study said. It analyzed 29 years' worth of data on koala sightings and animal hospital admissions from three wildlife rescue groups in New South Wales, Australia.
A combination of environmental impacts and human disturbance of koala habitats, researchers found, have made Australia's iconic marsupials vulnerable to extinction.
"In the last 10 years, we can see koala rescues ramped up significantly because more koalas are being found out in the open and on the ground," said lead author Edward Narayan, a senior lecturer of animal science at the University of Queensland.
That's not a good sign for a tree-dwelling species. For their survival, koalas rely on eucalyptus trees, which they use for food but also to find refuge and breed.