Koala populations hanging by a thread

New tracking has shown that koala populations are being impacted by habitat loss, which leaves them facing possible extinction.

A team of researchers from the ARC Centre of Excellence in Australian Biodiversity and Heritage (CABAH) pieced together the records of koala populations and their food trees up to 130,00 years ago — and projected their changing habitats into the future.

Koala populations have disappeared from Western Australia

Using a combination of climate, soil, and tree data, as well as records of koala fossils, the researchers developed sophisticated modelling to trace the impact of changing distributions of the eucalyptus trees on which koalas depend for food.

Their work reveals that prior to humans arriving in Australia, koala populations were found in the southern tip of Western Australia, and on the Nullarbor Plain that stretches from Western Australia to into South Australia.

The pattern of koala populations suggests that forests of eucalyptus trees extended across the continent in the past few hundred thousand years. But there has been a rapid loss of forests over the past 7,000 years. As the forests retracted eastwards, koala populations disappeared, and they are currently only found on the south-eastern and eastern coasts.

Farzin Shabani from Flinders University says that climate change has caused the species to become extinct in some parts of Australia.

“We found that climate change caused koala population extinctions in south-western Australia and in the Nullarbor Plain. We also showed that future climate patterns will likely increase the extinction risk of koalas in their remaining eastern ranges.”

Koalas are likely to face future declines

The study, published in the journal Ecography used mathematical models to predict the past and future distributions of 60 species of trees, mainly eucalyptus, that are eaten by koalas.

The researchers applied the same models to predict the distribution of eucalypt forests up to 2070 as the climate changes. In the face of other threats such as deforestation and disease, koalas are likely to experience future declines.

Lead researcher, Corey Bradshaw from Flinders University says there is hope for the most quintessential of Australian fauna — if action is taken to protect existing habitats and replace those already destroyed.

“Climate change has already reduced global biodiversity and will continue to do so, driving sometimes rapid shifts in the distributions and abundance of many species, and possibly driving many to local extinction in the near future. On that front, Australia and its unique species — the koala — is not exceptional.”

This article was first published on Australia’s Science Channel, the original news platform of The Royal Institution of Australia.