Almost lost: over 900 bird species

A COMBINATION of climate change and habitat destruction will significantly threaten 400 to 900 bird species by 2050, according to researchers who have carried out a global analysis of the effects of human activities on land-dwelling birds.

By the end of the century, the list will be roughly twice as long.

The birds at risk are those which the researchers predict will lose at least half of their habitat range. They said that although the effects of climate change are significant, they are dwarfed by damage to the birds' habitat due to, for example, logging to convert forest to farmland.

The analysis used data from the UN's Millennium Ecosystem Assessment (MEA) a five-year project begun in 2001 involving more than 1,300 experts worldwide, which aimed to provide a state-of-the-art appraisal of the world's ecosystems, the services they provide and how to conserve them.

The team used global political scenarios developed by the MEA to project what would happen to habitats over the next century.

Even with the most optimistic assumptions about global action on climate change and efforts to slow habitat destruction in the tropics, large numbers of the 8,750 land bird species were endangered.

"The big effect of climate change in terms of extinctions is in the Arctic and Antarctic," said Professor Dobson. Here, global warming is predicted to cause the biggest climatic changes. But there are fewer bird species the further you go from the equator and those near the poles also tend to have large ranges. That means they are more resistant to habitat loss. In the tropics it is a different story. "As you head to the tropics climate change still has an effect, but it seems to be totally masked by the land-use effects," said Prof. Dobson.

There are fewer bird species the further you go from the equator and those near the poles also tend to have large ranges. That means they are more resistant to habitat loss.

There are many more bird species close to the equator and those that are there tend to have much smaller ranges. So logging just one small stretch of forest can knock out an entire species' habitat. Overall, bird species will experience a 21% to 26% reduction in their range by 2050 and a 29% to 35% reduction by 2100.

The researchers say their analysis reveals the scale of the potential conservation disaster. "Only by rapidly expanding the network of protected areas in the tropics can we hope to prevent hundreds of species from becoming imperilled or even extinct," the team write in the journal Public Library of Science: Biology.

Tropical forests also provide an important buffer against climate change, the researchers say. So logging them is not only causing extinctions; it is also contributing to global warming. Prof. Dobson argues that developing countries should be paid for leaving their forests intact. "Probably the most valuable resource on the planet is the remaining wild areas," he said.

The research ties in with a paper in March which predicted that by the end of the century two-fifths of the planet would have a hotter climate unlike anything that currently exists. The researchers also predicted that the climatic conditions presently found on 10% to 48% of the Earth's surface would no longer exist anywhere. Some of the regions set to lose out are the tropical Andes, the African Rift mountains, the Zambian and Angolan highlands, the South African Cape region, southeast Australia, parts of the Himalayas and the Arctic.

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