Southern Australia’s koala comeback: what they can tell us about helping their threatened northern counterparts

Koalas are considered an endangered species in New South Wales, Queensland, and the ACT, but in some parts of South Australia and Victoria they’re having much greater success. They’ve recently made a comeback to Kangaroo Island and the Mount Lofty Ranges in SA, as well as safe “refuge” areas of Victoria.

The Adelaide Hills and Mount Lofty Ranges now have some of the densest populations of koalas in the country, with Belair National Park hosting as many as 14 koalas per hectare, says Flinders University Associate Professor Danielle Clode, who is the author of a new book Koala: A Life in Trees.

“It’s a far cry from some populations in inland Queensland, where barely a single koala per 100 hectares can be found,” says Clode, who will MC the NSW State Koala Conference in Coffs Harbour this weekend.

It’s only three generations ago that koalas were hunted to near extinction in SA, according to a pamphlet published by the SA Department of Environment and Natural Resources. But koalas cannot regulate their breeding according to the amount of available habitat and will continue to reproduce even when more koalas cannot be supported.

Flinders University researchers are studying the burgeoning SA koala populations and hope to contribute to research into rebuilding koala colonies on the east coast, devastated by bushfires and habitat loss.

Over-browsing is an issue

The koala conference on the 27 October 2022 is a summit of scientists, conservation groups and concerned citizens aiming to raise awareness of dramatic corrective action needed to save wild koalas faced with the threat of extinction along eastern Australia.

Clode told Cosmos the issue with koalas with really high population densities, like in Belair National Park and Morialta Conservation Park, is that they can over-browse the trees.

“A lot of these animals are descendants of the ones from French Island and Quail Island in Western Port near Melbourne. And they’re very famous for having over-browsed the islands, so much that the trees died, and the koalas died, and it was a huge tragedy.

“But they still seem to tend to do it, even in areas like the Mount Lofty Ranges, where they’re not necessarily restricted in where they can go.

Clode says it might be because the habitat has been fragmented and has created artificial islands in the landscape: “if you’ve got one little patch of the right trees surrounded by the wrong trees, effectively, it looks like forest but the koalas aren’t interested in it.

“So, we need to do more work around mapping that koala habitat and understanding where they can go where they won’t go.”

Mapping koalas in Belair National Park

Flinders University researchers have been conducting extensive studies of local SA populations and earlier this month initiated a demographic study in Belair National Park.

For ten days in October the team, led by Professor Karen Burke da Silva, captured, did health checks, tagged, and released 122 koalas – approximately a quarter to one fifth of the population that they estimate to be in the park. They intend to monitor the koala population for the next three years to estimate the rate of survival, reproduction, and dispersal.

Because the South Australian koala population is inbred but not threatened, understanding more about them will help to develop a framework to inform future potential genetic rescue attempts for inbred populations.

Clode asks: “what can we learn from the southern koalas’ success to help protect their northern cousins?”