Science solves South Australia’s koala dilemma

Research demonstrates the danger posed by over-abundant koala populations and offers humane solution.

Research into South Australia’s koala populations, led by Dr Frédérik Saltré from the Australian Museum and University of Technology Sydney (UTS), provides the first comprehensive population estimate for the region and identifies a cost-effective, humane solution to stabilise current unsustainable koala numbers.

Published in Ecology and Evolution, the study was led by Dr Frédérik Saltré who holds a joint appointment as a Research Scientist at the Australian Museum and Senior Lecturer in Ecology and Biogeography at UTS. The research, supported by Flinders University and the University of Wollongong, shows that South Australia’s koala population in the Mount Lofty Ranges, currently numbers around 10% of Australia's total population, which is threatening its long-term survival. Without intervention, this number could grow by a further 17–25% over the next 25 years, impacting food supply, vegetation and native habitats.

"Koalas are in steep decline across much of eastern Australia, but in South Australia's Mount Lofty Ranges, the opposite problem is happening: a booming koala population. This should be good news, but these numbers are concerning. Many areas now have koala densities far beyond what the ecosystem can sustain, creating a growing risk of severe over browsing that could rapidly damage the very forests koalas rely on for food. In the next few decades, following this trajectory, there will almost certainly be a terrible situation of mass koala starvation and death,” Dr Saltré said.

Using advanced spatial modelling and data from thousands of citizen science observations, researchers found koala densities in many areas are above what is considered sustainable.

“We are faced with a difficult conservation dilemma, because traditional methods of population management, like culling or relocation, either raise ethical concerns from the public or are not appropriate for such an iconic native animal. How do we manage a species that is now threatened by its own abundance, and do so in a way that protects both animal welfare and long-term ecosystem health?" Dr Katharina Peters, co-author of the study at the University of Wollongong said.

Dr Frédérik Saltré and his team found the answer through testing multiple fertility-control strategies, which demonstrated that sterilising approximately 22% of adult females annually, focusing on high-density hotspots rather than across the entire region, would stabilise the population at an estimated cost of $34 million over 25 years.

“The novelty lies in the proactivity of the approach: instead of spending money on a conservation plan without knowing whether it will succeed, we use computer simulations to identify in advance which strategies are most likely to work — optimising both costs and taxpayer investment,” Dr Saltré said.

As climate change continues to reshape habitats and species distributions, the researchers say such evidence-based and anticipatory approaches will become increasingly essential for managing high-profile species where public values and ecological needs collide.

This research builds on the previous work carried out at the Australian Museum in sequencing the approximately 20,000 genes in the koala to open up opportunities for medical treatments, provide knowledge about how koalas evolved, and indicate how best to conserve the species.

For media inquiries, email media@australian.museum

About the Australian Museum

The Australian Museum (AM) was founded in 1827 and is the nation’s first museum. It is internationally recognised as a natural science and culture institution focused on Australia and the Pacific. The AM’s mission is to ignite wonder, inspire debate and drive change. The AM’s vision is to be a leading voice for the richness of life, the Earth and culture in Australia and the Pacific. The AM commits to transforming the conversation around climate change, the environment and wildlife conservation; to being a strong advocate for First Nations cultures; and to continuing to develop world-leading science, collections, exhibitions and education programs. With 22 million objects and specimens and the Australian Museum Research Institute (AMRI), the AM is not only a dynamic source of reliable scientific information on some of the most pressing environmental and social challenges facing our region, but also an important site of cultural exchange and learning.

About University of Technology Sydney (UTS)

The University of Technology Sydney (UTS) has established itself as a leading university of technology located in the heart of Sydney’s innovation precinct. With more than 50,000 students, UTS is among the top 100 universities in the world and holds a reputation as a successful partner for research, industry and business. Championing social impact and sustainability, UTS has built a creative and innovative university with deep connections to its communities to affect positive change locally, nationally and globally.