South Australia’s koala population is booming, but researchers have warned that this seemingly successful koala population could eventually turn into a serious problem. New research provides the first comprehensive estimate of the region’s koala population and identifies humane and cost-effective strategies to maintain koala populations at sustainable levels.
This study ecology and evolutionwas led by Dr Frederic Sartre, Research Fellow at the Australian Museum and Senior Lecturer in Ecology and Biogeology at the University of Technology Sydney (UTS). The project also involved scientists from Flinders University and the University of Wollongong.
Koala population increases in South Australia
The study estimates that the koala population in South Australia’s Mt Lofty Ranges currently accounts for about 10% of all koalas in Australia. While that may sound like good news, researchers say the population has already reached levels that could threaten long-term survival.
The researchers predict that if no action is taken, the population could grow by an additional 17% to 25% over the next 25 years. Continued growth can increase pressure on food resources, native vegetation, and the broader ecosystem.
“Koala numbers are declining rapidly in many parts of eastern Australia, but in South Australia’s Mt Lofty Ranges, the opposite problem is occurring. Koala populations are rapidly increasing. This should be good news, but these numbers are alarming.
“Koala densities in many areas now far exceed what the ecosystem can sustain, raising the risk of severe overbrowsing and potentially rapidly damaging the very forests that koalas rely on for food. If we continue on this trajectory, we will almost certainly see a dire situation of mass starvation of koalas in the coming decades,” Dr Sartre said.
Computer modeling reveals future risks
To better understand the situation, researchers combined advanced spatial modeling with thousands of citizen science observations. Their analysis showed that koala densities are already above sustainable levels in many areas of the Mt Lofty Ranges.
The findings highlight difficult challenges for conservation managers. Traditional approaches such as culling and relocation are often controversial or considered inappropriate for a species that holds a special place in Australia’s wildlife heritage.
“We face difficult conservation dilemmas because traditional population management methods such as culling and relocation raise ethical concerns from the public or are not appropriate for such iconic native animals.
“How can we manage species whose abundance is currently threatened in a way that protects both animal welfare and long-term ecosystem health?” said study co-author Dr Katarina Peters from the University of Wollongong.
Fertility management offers a humane solution
The researchers used computer simulations to evaluate several population management options. Their results suggest that targeted fertility control programs can effectively stabilize koala numbers.
The most effective strategy was to sterilize about 22% of adult female koalas each year in the most densely populated areas, rather than applying this approach to the entire region. The research team estimates the program will cost about $34 million over 25 years.
“The novelty lies in the proactiveness of this approach. Rather than investing money in conservation programs that may or may not be successful, we use computer simulations to identify in advance which strategies are most likely to work, optimizing both costs and taxpayer investment,” said Dr. Frédéric Sartre.
Prepare for future conservation challenges
Researchers say proactive, evidence-based planning will become increasingly important as climate change continues to alter habitats and shift species distributions. They argue that scientific predictive tools can help decision makers balance ecological needs with societal concerns, especially when managing well-known and highly valued species.
The research also builds on previous Australian Museum work that successfully sequenced around 20,000 koala genes. This research expands opportunities for medical research, deepens our understanding of koala evolution, and provides new insights into how the species can be conserved in the future.
