Climate change could drive up to a sixth of animals and plants on Earth to extinction unless governments cut rising greenhouse gas emissions.
Species in South America, Australia, and New Zealand are most at risk, since many live in small areas or cannot easily move away to adapt to heatwaves, droughts, floods, or rising seas, according to the report in the journal Science.
It averaged out 131 previous studies of climate change, whose projections of the number of species that could be lost to climate change ranged from 0%- 54% of species worldwide — too wide to be useful in designing conservation policies.
Overall, it found that one in six species could be driven to extinction if greenhouse gas emissions are unchecked and temperatures rise by 4.3C above pre-industrial times by 2100, in line with one scenario from the UN Intergovernmental Panel on Climate Change.
“Perhaps most surprising is that extinction risk does not just increase with temperature rise, but accelerates,” said study author Mark Urban.
A temperature rise so far of 0.9C has put around 2.8% of species at risk of extinction, the study found. Governments plan a global deal at a UN summit in Paris in December to limit greenhouse gas emissions.
The study looked only at climate change, just one of many threats to wildlife including pollution, expanding cities, and loss of forests to farming that some experts say could trigger the worst extinctions since the dinosaurs died out 65m years ago.
While habitat loss and hunting are currently the top threats, climate change will be “the number one driver of extinctions in the medium to long term”, said Marco Lambertini, director general of the WWF conservation group.
Jamie Carr, a species expert at the International Union for Conservation of Nature (IUCN), said the study was a “very well-educated guess”, but that it was impossible to isolate the impact of warming from the host of other threats.
So far, he said, no species had been driven to extinction solely by a changing climate. The IUCN says warming contributed to the extinction of the golden toad, last seen on a Costa Rican mountaintop in 1989.
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