PARIS (AFP) - – Land ecosystems will have to move hundreds of metres each year in order to cope with global warming, according to a letter published on Thursday in Nature, the British-based science journal.
On average, ecosystems will need to shift 420 metres (about a quarter of a mile) per year to cooler areas this century if the species that inhabit them are to keep within their comfort zones, scientists in the US believe.
Flat ecosystems such as mangroves, wetlands and deserts face the biggest challenge, for they will have to move the farthest in order to survive.
Mountainous habitats are a bit luckier, as just a small shift in altitude provides some cooling.
The figures are based on the "A1B" scenario for likely carbon emissions this century, as forecast by the Intergovernmental Panel on Climate Change (IPCC). It is considered an intermediate level of warming.
Climate change would impact slowest in tropical and subtropical coniferous forests, temperate coniferous forests, so-called montane grasslands and shrublands, say the scientists.
Deserts, mangroves, grasslands and savannas would be hit fastest.
The paper suggests a ruthless Darwinian struggle will be unleashed.
Some rugged species may be able to adapt to warmer temperatures and modification of their home. Others that can migrate elsewhere in time will also survive.
But those species that cannot adapt -- or which move only slowly, such as plants -- will have nowhere to go and could face extinction.
"Expressed as velocities, climate-change projections connect directly to survival prospects for plants and animals. These are the conditions that will set the stage, whether species move or cope in place," said co-author Chris Field, director of the Carnegie Institutions Department of Global Ecology.
The study says that protected areas such as nature reserves are generally too small to cope with the expected habitat shifts.
Less than 10 percent of protected areas globally will maintain current climate conditions within their boundaries a century from now, it warns.
Under the A1B scenario, the best estimate of a UN's Nobel-winning panel of climate scientists foresees a temperature rise this century of 2.8 degrees Celsius (5.04 degrees Fahrenheit), in a range of 1.7-4.4 C (3.06-7.2 F).
A group of world leaders, at the Copenhagen climate summit last Friday, set the goal of limiting warming to 2 C (3.6 F), but did not explicitly say whether the benchmark was since industrial times or over the course of this century.
There has already been around 0.7 C (1.26 F) of warming since the start of the Industrial Revolution of the mid-18th century, when the burning of coal, oil and gas began the greenhouse-gas phenomenon.