Koalas at risk of extinction as climate change eats up habitat

Koalas are at risk of extinction if we cannot reverse the effects of long-term climate change, new research has found.

Fauna Rescue of South Australia koala co-ordinator Merridy Montarello with Frank and Fish. Picture: Bianca De Marchi

Koalas are at risk of extinction due to long-term climate change, research indicates.

It comes as fur flies over wildly varying estimates of local koala populations and efforts to control numbers by sterilisation and contraceptives — including a new program in the Adelaide Hills.

Flinders University’s Corey Bradshaw, chief investigator for the Centre of Excellence in Australian Biodiversity and Heritage, said studies show the koala range in Australia could reduce by about 60 per cent by 2070.

“Over the last 20,000-odd years, forests have been shrinking,” he said.

The research suggests eucalypt forests once extended across the continent but there had been a rapid loss of habitat.

Koalas are extinct in southwestern Australia and across the Nullarbor Plain and Prof Bradshaw said further loss of habitat due to climate change puts them at risk on the southeastern and eastern coasts.

He said it was estimated there were now 100,000-200,000 koalas in the Mount Lofty Ranges but these were “highly inbred” after growing from just six animals reintroduced in 1965.

However, Fauna Rescue volunteers Merridy Montarello and Dee Hearne-Hellon doubted the estimate, saying it relies on citizen science counts.

“When you see how little habitat there is, it’s ludicrous to think there’s 200,000, or even 100,000,” Mrs Hearne-Hellon said. “How do you know a koala hasn’t been counted four or five times?”

Based on much smaller population estimates by the Australian Koala Foundation — about 80,000 across Australia — they believe the marsupials could be extinct in SA by 2045.

Prof Bradshaw said koala count used was “a very established technique” and while the Australian Koala Foundation’s concerns about the marsupials on the east coast were warranted, said: “there certainly aren’t 80,000 — there’s much more than that”.

The State Government has a program of sterilising koalas on Kangaroo Island, in a bid to reduce the population and improve tree health. Mrs Hearne-Hellon is concerned about moves to sterilise the marsupials on the mainland, including a new program in the Adelaide Hills which started last month.

An Environment Department spokeswoman said South Australia’s koala population was “unsustainably high” in some parts of the Mount Lofty Ranges and on Kangaroo Island.

“The population continues to increase at both sites,” she said.

The Government has had a longstanding sterilisation program on Kangaroo Island, but this year began using contraceptive implants to control koala populations on the island, and also in the Adelaide Hills.

“The aim is to reduce koala breeding to a sustainable level to protect native vegetation, and reduce the risk to the koalas themselves of food shortages caused by over-browsing,” she said.

“(The department) is working in collaboration with researchers to ensure a sustainable South Australian koala population that continues to thrive with enough food and habitat.”