Koalas are now considered an endangered species in NSW, Queensland and the ACT, as numbers plummet due to climate change, land clearing and disease.
The Australian icon had previously been rated "vulnerable" under the federal government's Environment Protection and Biodiversity Conservation Act 1999, but its status has now been upgraded.
Federal Environment Minister Sussan Ley says the endangered listing means conserving the koala is given greater priority.
She said the CSIRO's best estimate about how many koalas were left in the wild was a population of about 180,000 along the east coast.
Ms Ley told ABC Radio Brisbane the government had not set targets for koala population growth, but was seeking to develop "resilient" populations ahead of any future natural disasters.
She said the government had asked CSIRO to develop a comprehensive mapping tool for koala populations, including their disease status.
But the 180,000 figure was labelled "nonsense" by the Koala Foundation's Deb Tabart, who said the wild koala population was estimated to be much lower at around 50,000-80,000 nationally.
"In 2019, just after the bushfires, that Minister Ley had all of us down there at a round table and I handed her the koala habitat atlas of the entire geographic range of the koala, which has taken us 23 years to create," Ms Tabart said.
"I gave her our estimate of the koala numbers, which at the time was about between 50-80,000 koalas ... across the whole country."
Ms Tabart said her organisation estimated there had been a 30 per cent reduction in koala populations since 2018, a figure supported by other experts.
Ms Ley said she was relying on the experts in her scientific committee for koala population estimates and advice on future management plans, but data across the states was patchy.
"Given we don't know where more disease may hit, we don't know where more bushfires may strike, we don't know necessarily what the future holds, so we have to build the resilience now to get the highest number that we can," Ms Ley said.
The government requested the Threatened Species Scientific Committee — a Commonwealth agency that provides independent advice to the Environment Minister — to review the koala's status in the wake of the Black Summer bushfires, which wiped out significant amounts of habitat.
Ms Ley cited the impacts of climate change, land clearing and disease as the key threats facing the koala.
According to a report by the Australian Koala Foundation released in September, there were between 32,065 and 57,920 koalas left in the wild last year.
It claimed the biggest declines were in NSW, where koala numbers dropped 41 per cent since 2018.
Under the act, threatened species are classified in six ways in Australia:
- extinct
- extinct in the wild
- critically endangered
- endangered
- vulnerable
- conservation dependent
Environmental groups said saving the koala would require urgent action from all levels of government.
"National environment laws have fundamentally failed to provide the protection the koala needs," said Basha Stasak from the Australian Conservation Foundation (ACF).
"What we need to see the government do is stop destroying koala habitat."
The federal government has approved more than 25,000 hectares of koala habitat since the species was declared "vulnerable" 10 years ago, according to the ACF.
Ms Ley defended the government's record on land clearing.
"We do look at developments and we do assess them and make necessary offsets for koala habitat."
Stuart Blanch, from the World Wildlife Fund, said the new listing was "grim but important".
"It helps people who want to save koalas to do the right thing," he said.
"That's ministers who make decisions on development, it's treasury officials who work out whether to put money into funding farms to support koalas or buying up native logging wood supply agreements in koala country."
Ms Ley said the federal government had committed $50 million to koala conservation and protection.
She said the government was connecting corridors of koala habitat in northern NSW and southern Queensland as well as planting new trees.
