More than half of common species of plants and a third of animal species are likely to see their living space halved by 2080 on current trends of carbon emissions, a climate study said on Sunday.
Output of man-made greenhouse gases is putting Earth on track for four degrees Celsius (7.2 degrees Fahrenheit) of warming by 2100 compared with the pre-industrial 18th century, it said.
The unprecedented speed of warming will be a shock for many species, as it will badly affect the climatic range in which they can live, it warned.
Investigators from Britain's University of East Anglia looked at 48,786 species and measured how their range would be affected according to models of carbon dioxide (CO2) emissions.
Fifty-five percent of plants and 35 percent of animals could see their living space halved by 2080 at current emission growth for CO2, they found. The figures take into account the species' ability to migrate into habitat that may open up as a result of warming.
The species most at risk are amphibians, as well as plants and reptiles, and regions that would lose most are Sub-Saharan Africa, Central America, Amazonia and Australia, the paper said.
Lead researcher Rachel Warren said the estimates "are probably conservative" as they were based only on the impact of rising global temperatures.
Other symptoms of climate change -- storms, droughts, floods and pests, for instance -- would amplify the problem.
"Animals in particular may decline more as our predictions will be compounded by a loss of food from plants," Warren said in a press release.
"There will also be a knock-on effect for humans because these species are important for things like water and air purification, flood control, nutrient cycling and eco-tourism."
The study, published in Nature Climate Change, said there was a ray of light.
If carbon emissions peak in 2016 -- and decline by three to four percent annually thereafter -- this would limit 2100 warming to 2 C (3.6 F), avoiding around 60 percent of the projected impact from business-as-usual emissions.
But if the peak is delayed until 2021, emissions would have fall yearly by six percent to achieve 2 C (3.6 F) warming, which would need a costlier effort to rein in energy use.
Alternatively, if emissions peak by 2030 and then are reduced at five percent annually to limit warming to around 2.8 C (5 F), the loss of climatic range would be reduced by 40 percent compared with business-as usual.
UN members have adopted the 2C target in world climate talks, which aim to conclude a new treaty on carbon emissions by 2015 and have it ratified by 2020.
But the negotiations have been making poor progress, and the yearly rise in emissions, driven especially by the burning of coal in big developing countries, has led many scientists to conclude that warming of 3 or 4 C (5.4-7.2 F) is probable by century's end.
The new study says that loss of climate range would be bound to boost the risk of species extinction.
The Nobel-winning Intergovernmental Panel on Climate Change (IPCC) has estimated that 20-30 percent of species would be at increasingly high risk of extinction if warming exceeds two or three C (3.6-5.4 F) above pre-industrial levels.