Koala Conservation Milestone Achieved, But Challenges Persist: 'This Should Be Good News

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Koalas are endangered across much of eastern Australia, but in pockets of South Australia and Victoria, populations are booming — raising a different set of concerns.

New research suggests the koala population in some areas of South Australia’s Mount Lofty Ranges has reached unsustainable levels, meaning koala numbers could outstrip available habitat and food.

The study, led by the University of Technology Sydney (UTS) and the Australian Museum, estimated the region is home to roughly 10 per cent of Australia’s total koala population, and could grow a further 17 to 25 per cent over the next 25 years.

“While these figures seem promising, they also raise some concerns,” stated Frédérik Saltré, an expert in ecology and biogeography at the University of Technology Sydney.

Saltré told SBS News that over time, unchecked growth could lead to overbrowsing, which damages trees the marsupials rely on for food and shelter.

If the trajectory continues, “down the track, not tomorrow, not next week, but years down the track, they’re not going to have enough food to survive, and they might starve to death,” he said.

This could also change the ecosystem for other species that depend on eucalyptus trees, and result in dead tree material that could fuel increasingly frequent bushfires, he said.

The researchers behind the study are proposing fertility control measures in certain high-density hotspots to stabilise the population at an estimated cost of $34 million over 25 years.

There is a divide among conservationists about how to interpret these findings, with some advocating caution until more detailed and up-to-date data is analyzed.

In South Australia, koalas have thrived due to a combination of factors: fewer natural predators, less urban development compared to Queensland and New South Wales, a more stable climate, and an abundance of their preferred eucalyptus trees, according to Saltré.

In the early 20th century, after decades of hunting and habitat clearing, koalas were at risk of extinction in Australia’s south.

However, in the 1920s, 18 koalas were introduced to South Australia’s Kangaroo Island from French Island in Victoria. Their numbers rapidly increased.

Several decades later, koalas from Kangaroo Island were introduced to several other locations in South Australia, including the Mount Lofty Ranges.

It’s important to note that koalas remain classified as endangered in Queensland, New South Wales, and the Australian Capital Territory.

Karen Burke da Silva, a professor of biodiversity and conservation and head of the Koala Conservation Hub at Flinders University, said it was a “huge conservation success”.

“This population, especially the one on Kangaroo Island that has no chlamydia and no active koala retrovirus, can be extremely important into the future as the populations on the east coast decline,” she told SBS News.

In some pockets, koalas became overabundant, meaning populations grew beyond what local habitats could support.

As a result, the state government introduced a variety of management techniques, including sterilising animals, implanting them with hormonal contraception, and translocating them.

More than 13,500 koalas have been sterilised or given contraception since 1996, according to the South Australian government.

“Based on the data we have, it appears that koala population numbers in South Australia have remained relatively stable over the past few years,” a conservation expert noted.

Concerns about acting too soon

Burke da Silva noted that the study used a predictive model leaning on citizen scientist survey data from 2012 and 2016.

She said there is newer, quality data on koala populations coming in through the National Koala Monitoring Program, which will provide valuable inputs for future modelling efforts.

“We don’t want to start making claims or recommendations until we know how many koalas are actually out there,” she said, pointing to the likely devastating impacts of recent bushfires.

Experts are working toward a better understanding of actual koala numbers across Australia and South Australia through the national monitoring program.

“Our current understanding from our data is that there’s been very little to no change in population numbers across the last few years,” she said of South Australian figures.

A koala joey on its mother's back on a tree.

Relocating koalas is difficult and expensive, and causes stress to the animal. Source: AAP / WWF

The model is “sophisticated and really cutting edge,” Burke da Silva said, and could be a great resource when coupled with more robust, recent data.

She also emphasised that overbrowsing typically occurs in small, localised areas, which require boots-on-the-ground identification.

“If we get the data that can showcase that really high densities of koalas in some areas are causing impact on the vegetation, then we target those areas, and that’s where a fertility control can occur,” she said.

Saltré said the model could be adjusted with new data, and pointed out that issues like disease, climate change and increased bushfire risks had not been accounted for in the study.

Climate change-driven events can amplify habitat loss, while bushfires and droughts can have catastrophic implications for koala populations.

Chlamydia, a major issue for koala populations, can lead to infertility and death.

Why fertility control? Can koalas be relocated?

Koala overabundance is a complicated issue. Relocation is extremely stressful for koalas, and is also “very expensive and not always successful,” Saltré said.

Last year, an attempt to translocate 13 koalas from near Wollongong to a national park in NSW’s south resulted in the majority of the animals dying.

Other methods of population control, such as culling, are banned.

Saltré’s team estimates that applying fertility controls to 22 per cent of adult females annually, focusing on high-density hotspots only, could help make the population more sustainable.

Contraceptive implants can be removed if they need to course correct, he noted.

However, with koalas living up to 15 years, these interventions can take time to show results.

“The problem with a sterilisation program is the animals continue to feed on those trees for long periods of time,” Burke da Silva said.

“So how quickly it can work is questionable, but also whether it’s needed, especially in areas impacted by chlamydia, where fertility is quickly being reduced.”