Global warming creeps across the world at a speed of a quarter of a mile each year, according to a study that highlights the problems rising temperatures pose to plants and animals.
Species that can tolerate only a narrow range of temperatures will need to move as quickly if they are to survive, and wildlife in lowland tropics, mangroves and desert areas are at greater risk than species in mountainous areas, the study suggests.
“These are the conditions that will set the stage, whether species move or cope in place,” said Chris Field, director of the global ecology unit at the Carnegie Institution in the U.S., who worked on the project. “Expressed as velocities, climate change projections connect directly to survival prospects for plants and animals.”
The study, by scientists at the Carnegie Institution, Stanford University, the California Academy of Sciences, and the University of California, Berkeley, combined information on current and projected climates to calculate a “temperature velocity” for different parts of the world.
They found mountainous areas would have the lowest velocity of temperature change, meaning animals would not need to move very far to stay in the temperature range of their natural habitat. However, much larger geographic displacements would be required in flatter areas, such as deserts, to allow animals to keep pace with their climate zone.
The researchers also found most areas now protected were not big enough to accommodate these displacements.
Healy Hamilton, director of the Centre for Applied Biodiversity Informatics at the California Academy of Sciences, said the data allowed evaluation of how the current protected area network would perform as attempts were made to conserve biodiversity. “When we look at residence times for protected areas, which we define as the amount of time it will take current climate conditions to move across and out of a given protected area, only 8 per cent of our current protected areas have residence times of more than 100 years. If we want to improve these numbers we need to reduce our carbon emissions and work quickly towards expanding and connecting our global network of protected areas.”
The study found that global warming would have the lowest velocity in tropical and subtropical coniferous forests, where it would move at about 80 metres a year, and in montane (upland areas below the treeline) grasslands and shrublands, where the projected velocity was about 110 metres a year.
The results, published in the journal Nature, show global warming is expected to sweep more quickly across flatter areas such as mangrove swamps and savannas, where it could have velocities above 1 km a year. Across the world, the average velocity is 420 metres a year.
Wildlife in areas with low projected climate-change velocities will not necessarily be better protected, the scientists say. Habitats such as broadleaf forests are often small and fragmented, which makes it harder for species to move. The scientists stress it is difficult to predict what the impact would be on individual trees, insects and other animals.
While trees are estimated to have spread north through Europe after the end of the last ice age at a speed of about 1km a year, this could be due to re-seeding by dormant seeds, which would not be possible if species had to shift to new territories.
The scientists say global warming will cause temperatures to alter so rapidly almost a third of the globe could see climate velocities higher than even the most optimistic estimates of plant migration speeds. Some species might have to be moved by people, and protected areas joined up and enlarged. — © Guardian Newspapers Limited, 2009
