Research published in Ecology and Evolution estimates that the koala population in South Australia’s Mount Lofty Ranges accounts for about 10 per cent of all koalas in Australia – and this density could threaten the long-term survival of the species.
To evaluate how this population density could affect future koala populations, scientists combined advanced spatial modelling with thousands of citizen science reports.
According to the researchers, the koala population in the area could increase by another 17 to 25 per cent over the next 25 years – which would put pressure on food resources, native vegetation and the wider ecosystem.
“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,” explains the study’s lead author Frédérik Saltré, who is a research scientist at the Australian Museum and a senior lecturer at the University of Technology Sydney.
“In the next few decades, following this trajectory, there will almost certainly be a terrible situation of mass koala starvation and death.”
Koalas are not abundant across Australia – the species is in decline in the east of the country. This concerningly dense population in the south of the continent therefore poses a challenge for conservation managers.
“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,” says Katharina Peters, a co-author of the study at the University of Wollongong, Australia.
Conserving koalas
As part of the study, the researchers assessed the efficiency and cost-effectiveness of koala fertility-control interventions. The results suggested that a programme focusing on adult female koalas could be the most cost-effective.
This would involve sterilising around 22 per cent of adult female koalas each year in areas with the highest population densities. It’s estimated the programme will cost approximately $34 million over a 25-year period.
However, a programme that focuses on sterilising young female koalas was found to be much faster at reducing population size – demonstrating the complex challenges conservationists face.
“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,” added Saltré.
Read the full research paper here.
Top image credit: JurgaR/Getty Images
