Researchers warn that a koala population boom in South Australia's Mount Lofty Ranges—now home to roughly 10% of the nation's koalas—may outstrip available eucalyptus food, risking a starvation-driven crash. Spatial models and thousands of citizen science records show local densities already exceeding sustainability thresholds and project a further 17–25% rise over 25 years if trends continue. The authors do not advocate culling; they explore targeted fertility control focused on age groups, hotspots and locations as a humane option, while noting uncertainties about scaling such interventions.
Koala Boom in South Australia Is Stripping Forests Bare — Scientists Warn of Starvation Crash
Photo Credit: iStock
What began as a hopeful recovery for koalas in South Australia is stirring alarm among scientists. New research indicates that rapid population growth in parts of the Mount Lofty Ranges is outpacing the ability of local eucalyptus forests to regenerate, increasing the risk of a severe, starvation-driven population crash.
Mount Lofty Ranges Hold A Significant Share — The study estimates that the Mount Lofty Ranges now support about 10% of Australia’s koalas. If current trends continue, model projections suggest the population there could rise another 17–25% over the next 25 years, putting further pressure on preferred eucalyptus species.
Mapping Pressure With Models And Citizen Science — Researchers combined spatial population models with thousands of citizen science records to map where koala densities are highest. Their analysis shows that some pockets already exceed the South Australian government’s sustainability benchmarks, raising the specter of a boom-and-bust collapse similar to the documented decline at Victoria’s Cape Otway.
Why Overbrowsing Matters
When koalas consume preferred eucalyptus leaves faster than trees can recover, the effects ripple through ecosystems: reduced habitat and food for other native animals, lower biodiversity, diminished recreational and cultural values, and weaker climate resilience. Healthy forests also store carbon, so their degradation has broader environmental consequences.
These risks are amplified in fragmented landscapes where predators are scarce and animals have limited ability to disperse. In such circumstances, rapidly rising herbivore numbers can destabilize ecosystems rather than restore balance, leaving communities and governments to face more difficult and costly interventions later.
Management Options: Humane, Targeted, and Uncertain
The researchers explicitly stop short of recommending culling. Instead, the study explores targeted fertility-control approaches aimed at specific age classes, high-density hotspots, or defined locations as a more humane way to slow population growth before mass starvation occurs. The authors note important uncertainties: the findings rely on citizen science data and modeling, and the real-world effectiveness and logistics of large-scale fertility-control programs in wild koala populations remain to be proven.
As Dr. Katharina Peters of the University of Wollongong said: "Nobody wants to see koalas being culled or starved because their habitat cannot sustain their numbers. That's why it's so important to manage the population and prevent it from becoming too large."
The study underscores a difficult conservation truth: legal protection alone does not guarantee a sustainable recovery if habitat capacity is limited. Proactive, humane management that couples population measures with habitat protection and restoration offers the best chance to avoid future crises.
Help us improve.
