If world leaders fail to take action and climate change continues unabated, researchers say that one in six of the planet's species could be lost to extinction.
A new meta-analysis of more than 100 published studies has provided one of the most comprehensive examinations of the impact on biodiversity in a warming climate.
Rather than matching temperature change in a linear fashion, the loss of biodiversity accelerates with every degree of global warming, as shown by the study, which was published in the journal Science.
The root cause, identified in almost all the analyzed studies, is climate change — which shrinks the geographic range of a species' habitat. Unless that species can move to a similar area or adapt to a different environment, it can easily die out.
"Species were predicted to become extinct if their range fell below a minimum threshold," said study author Mark C. Urban from the University of Connecticut.
The global regions that will face the most severe impact on biodiversity as a result of climate change are Australia, New Zealand and South America. The researchers explained that this is because of the high number of species found in just those regions and nowhere else in the world.
The study comes as almost 200 governments are preparing for a climate summit in Paris this December. There, they will try to hammer out a global agreement on limiting carbon emissions in an effort to halt – or at least slow – global warming.
Even if global warming can be held to 2 degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial levels – a goal from previous climate summits — one species out of every 20 would still face the risk of extinction. If the increase in temperature exceeds 4 degrees by the end of the century – a solid possibility, if the current record-breaking rate of greenhouse gas emissions is not reduced – that extinction rate could hit one in six.
"The risk, if we continue on our current [climate] trajectory is very high," said Urban. "If you look out your window and count six species and think that one of those will potentially disappear, that's quite profound."
Still, he continued, some of the predicted extinctions could be slow in coming and take a protracted time, suggesting that targeted conservation efforts for some at-risk species could help them survive a warmer world. And other species may be able to adapt to changing conditions enough to survive.
"This isn't just doom and gloom," he added. "We still have time. Extinctions can take a long time."