The habitats of more than 90 per cent of Australia's gum tree species will on average halve in size, and 16 eucalypt species are likely to become extinct, over the next 70 years due to global warming, a new international study has found.
The research also helps to identify regions across Australia that will be important for the evolution of eucalypts and for the preservation of rare, ancient species.
Dr Dan Rosauer from The Australian National University (ANU), a researcher in the study published in Nature Climate Change, said the drastic loss of habitat for eucalypt species may result in the creation of a very different Australian environment.
"Eucalypts dominate so much of Australia, providing habitat for countless flora and fauna species, and they have a special place in the identity of many Australians," said Dr Rosauer, a scientist at the ANU Research School of Biology.
"They represent millions of years of evolutionary heritage unique to our region."
Dr Rosauer said the habitats for most eucalypt species would shift south and to higher altitude.
"We've mapped the hotspots of eucalypt diversity and our study shows that by 2085 the hotspots will be in different places. We need to plan now to conserve those future hotspots."
Based on a forecast that global temperatures would increase three degrees Celsius above pre-industrial levels by 2070, the research predicts the habitats for 91 per cent of the 657 eucalypt species studied will shrink in size, by 51 per cent on average, within the next 70 years.
"We predict that habitat for 16 eucalypt species will disappear altogether, while nine per cent of eucalypt species could actually benefit from climate change over the same time period," Mr Rosauer said.
He said Australia's southern, southeast, and southwest coasts would become highly important for the conservation of both old and recently evolved eucalypt species, while the Kimberley region will increasingly be a refuge for rare, ancient lineages.
Co-researcher Dr Carsten Kulheim from the ANU Research School of Biology said the habitat loss due to climate change was not distributed equally across eucalypt species.
"Rare, old species are most severely affected," Dr Kulheim said.
"We predict loss of eucalypt diversity within regions and an increased homogenisation over the landscape, meaning less difference between regions."
Associate Professor Bernd Gruber from the University of Canberra, which led the research, said the study was the first to examine the impact of climate change on the distribution of a large group of closely related tree species at a continental scale.
"This study demonstrates the importance of not simply counting the number of species in biodiversity conservation, but also considering their evolutionary history which determines how closely related species are to each other," Dr Gruber said.
"Using this approach we were able to identify hotspots that will contain high levels of eucalypt diversity under a changing climate, both in terms of the number of species and their reflection of the trees' evolutionary pathways. Protecting these hotspots will be important to ensure we retain biodiversity in the future."
To build the family tree of eucalypts, Dr Andrew Thornhill, based at the University of California, Berkeley, in the United States obtained DNA from the leaves of more than 700 eucalypt species, many of which are cultivated in Australian National Botanic Gardens.
Dr Laura Pollock from the University of Grenoble Alpes in France used a supercomputer to predict the future distribution of each eucalypt species across Australia.
ANU conducted the research in collaboration with Australian and international institutions: University of Canberra, CSIRO, University of New South Wales, James Cook University, Macquarie University, Griffith University, University of Queensland, University of Melbourne, the Australian Museum, Colombian Agricultural Research Corporation (Corpoica), University of Grenoble Alpes in France, and University of California, Berkeley, and National Science Foundation in the US.