Saving our koalas: using genomics to enhance conservation outcomes

Koalas in New South Wales are at risk of extinction by 2050. New research highlights the need for targeted conservation efforts to address genetic diversity and maintain habitat connectivity to ensure their survival.

Few animals have captured the popular imagination quite like the koala. Their unusual, laid-back lifestyle, coupled with their cute, fluffy appearance, has made them an iconic symbol of Australia’s unique native wildlife. Unfortunately, this popularity has not spared koalas from the threat of extinction. A large body of evidence, collected over nearly four decades, demonstrates that koala populations across New South Wales (NSW) are declining due to a combination of rapid habitat destruction, climate change, disease, dog attacks, and vehicle strikes. The situation has become so dire that a 2020 Legislative Council inquiry into NSW koala populations and habitat concluded that, without further action, koalas could disappear from the state of NSW entirely by 2050. However, despite near universal public support, ongoing attention from the scientific community, and unprecedented financial investment by both the State and Federal governments, key knowledge gaps persist that could hinder the effectiveness of koala conservation efforts. One of the most important of these knowledge gaps, as addressed by both the NSW Koala Strategy 2022 and the NSW Chief Scientist and Engineer's Report, is an understanding of the processes that have shaped the distribution of genome-wide genetic diversity.

Surprisingly little is currently known about the levels or distribution of genetic diversity in NSW koalas. Collecting this information is therefore essential for determining the overall vulnerability of regional and local koala populations to different threatening processes (such as inbreeding or a reduced ability to adapt to rapid environmental change) and, by extension, their priority for targeted conservation actions. To address these knowledge gaps, a group of scientists, led by researchers at the Australian Museum, have analysed genetic markers called single nucleotide polymorphisms (or SNPs) from more than 300 individual koalas.

Our results indicated that there are at least five genetically distinct groups of koalas across NSW, and that established state-level management divisions (which are derived from the Areas of Regional Koala Significance or ARKS developed by the NSW Department of Planning and Environment) do not fully represent their distribution. Most of these groups were found to span multiple ARKS, while one ARKS was found to contain at least two genetically distinct groups of koalas. As a result, care must be taken to ensure that conservation actions (e.g., translocations) based on management divisions derived from these ARKS do not inadvertently restrict gene flow between regions or populations that are likely to have been historically interconnected. We also found evidence that koalas from the Liverpool Plains and southern NSW are relatively isolated from the rest of the state, and have proportionally lower levels of genetic diversity as a result. Consequently, these populations may be particularly vulnerable to environmental disturbances caused by human activity.

Finally, our research shows that while there are quantifiable genetic differences between the five groups of koalas that were identified by our analyses, it is relatively small compared to genetic variation amongst individual koalas. This leads us to conclude that koala populations should be prioritised for conservation action based on the scale and severity of the threatening processes that they are currently faced with, rather than placing too much emphasis on their perceived value (e.g., as reservoirs of potentially adaptive gene variants). As no one group of koalas contains a majority of existing variation, the loss of koala populations from any part of their range represents a potentially critical reduction of genetic diversity for the entire species. To improve conservation outcomes, it is therefore absolutely vital that we reduce koala mortality rates across the entire State by addressing the route causes of population declines (e.g., habitat loss) while maintaining habitat connectivity between as many surviving populations as possible.