8 January 2004The Independent
A quarter of known land animals and plants, more than a million species, will eventually die out because of the global warming that will take place over the next 50 years, the most important study of its kind has concluded.
International scientists from eight countries have warned that, based even on the most conservative estimates, rising temperatures will trigger a global mass extinction of unprecedented proportions.
They said global warming will set in train a far bigger threat to terrestrial species than previously realised, at least on a par with the already well-documented destruction of natural habitats around the world.
It is the first time such a powerful assessment has been made and its conclusions will shock even those environmentalists accustomed to "worst-case" scenarios.
Professor Chris Thomas, a conservation biologist from Leeds University who led the research team, said only the "immediate" switch to green technologies and the active removal of carbon dioxide from the atmosphere could avert ecological disaster. "It will be a surprise to a lot of people," he said. "For some years scientists have said climate change may lead to some extinctions but until now there's been no numerical analysis of how big this is likely to be. We had no idea of whether it would lead to the extinction of a few species or a really substantial number. This study suggests the latter and it's extremely worrying.
"If the projections can be extrapolated globally, and to other groups of land animals and plants, our analyses suggest that much more than a million species could be threatened with extinction as a result of climate change."
The study, in the journal Nature, investigated 1,103 species of plants, mammals, birds, reptiles, frogs, butterflies and other insects living in six areas - Europe, South Africa, Australia, Brazil, Mexico and Costa Rica.
The scientists calculated the effect of rising temperatures on each species using the three future scenarios proposed by the UN's intergovernmental panel on climate change (IPCC) which has predicted minimum, mid-range and maximum global average temperature increases of between 0.5C to 3C by 2050.
Based on the knowledge of the relatively gradual onset and aftermath of an ice age - and of the past 30 years of dramatically rising temperatures - the scientists were able to assess whether the expected climate change would result in a species shifting to a cooler region, or not.
A warmer world would push most species towards the poles or higher up mountains but for many this would be impossible. The home territories of those that could move might be so reduced as to make a breeding population unviable.
The study found:
* Of Australia's more than 400 butterfly species, of which nearly 200 are unique to the continent, all but three might not survive in the present home ranges. More than half could be wiped out.
* Brazil's unique savannah grassland the Cerrado faces disaster with some 45 per cent of the endemic plants - some 2,000 species - facing extinction.
* In Europe, the study predicts a 25 per cent extinction rate for birds under the maximum temperature scenario of the IPCC.
* In Mexico's Chihuahuan desert, extinction would be particularly high because threatened species would have to travel long distances to reach cooler climates.
* In South Africa's Cape Floristic region, the scientists believe between 30 and 40 per cent of the Proteaceae, a family of flowering plants that includes South Africa's national flower, the king protea, will die.
* In Costa Rica's Monteverde cloud forests, warmer temperatures would increase the altitude at which clouds form and even prevent their formation.
Lee Hannah, a senior fellow at the Centre for Applied Biodiversity Science at Conservation International in Washington DC, said the combination of habitat loss and global warming would mean that there would be no safe havens even for some of the most-protected species.
"This study makes it clear that climate change is the most significant new threat for extinctions this century," Dr Hannah said. "The combination of increasing habitat loss, already recognised as the largest single threat to species, and climate change, is likely to devastate the ability of species to move and survive."
