Modelling climate-change-induced shifts in the distribution of the koala

Context The impacts of climate change on the climate envelopes, and hence, distributions of species, are of ongoing concern for biodiversity worldwide. Knowing where climate refuge habitats will occur in the future is essential to conservation planning. The koala (Phascolarctos cinereus) is recognised by the International Union for Conservation of Nature (IUCN) as a species highly vulnerable to climate change. However, the impact of climate change on its distribution is poorly understood. Aims We aimed to predict the likely shifts in the climate envelope of the koala throughout its natural distribution under various climate change scenarios and identify potential future climate refugia. Methods To predict possible future koala climate envelopes we developed bioclimatic models using Maxent, based on a substantial database of locality records and several climate change scenarios. Key results The predicted current koala climate envelope was concentrated in south-east Queensland, eastern New South Wales and eastern Victoria, which generally showed congruency with their current known distribution. Under realistic projected future climate change, with the climate becoming increasingly drier and warmer, the models showed a significant progressive eastward and southward contraction in the koala’s climate envelope limit in Queensland, New South Wales and Victoria. The models also indicated novel potentially suitable climate habitat in Tasmania and south-western Australia. Conclusions Under a future hotter and drier climate, current koala distributions, based on their climate envelope, will likely contract eastwards and southwards to many regions where koala populations are declining due to additional threats of high human population densities and ongoing pressures from habitat loss, dog attacks and vehicle collisions. In arid and semi-arid regions such as the Mulgalands of south-western Queensland, climate change is likely to compound the impacts of habitat loss, resulting in significant contractions in the distribution of this species. Implications Climate change pressures will likely change priorities for allocating conservation efforts for many species. Conservation planning needs to identify areas that will provide climatically suitable habitat for a species in a changing climate. In the case of the koala, inland habitats are likely to become climatically unsuitable, increasing the need to protect and restore the more mesic habitats, which are under threat from urbanisation. National and regional koala conservation policies need to anticipate these changes and synergistic threats. Therefore, a proactive approach to conservation planning is necessary to protect the koala and other species that depend on eucalypt forests.