Richard Thomas: How habitat destruction fuels tide of extinction

Like the world's oceans under climate change, the tide of extinction has been creeping higher and faster in recent decades. But there are - often literally - islands of hope, where conservation has brought some of the world's most threatened birds back from the brink.

BirdLife International, the global alliance of national conservation organisations including the RSPB, says that, between 1994 and 2004, 16 bird species were reprieved from otherwise certain extinction. Most numbered fewer than 100 in 1994. The average was 34 birds, with one, the Chatham Island taiko, down to four breeding pairs. The 37 Norfolk Island parrots included four breeding females.

Determined action has brought back species with even smaller populations, such as the black robin: two females among five individuals in 1980; 300 birds in 2004. By 2004, the average population for the 16 species had increased to 147 individuals. Norfolk Island parrot and Mauritius parakeet (five pairs in 1994) had gone up tenfold.

The main threats to these species were - and still are - habitat destruction, predation by introduced species like rats, cats, mongoose and pigs, and human exploitation, particularly by the bird trade. Most of the work was done by governments working with conservation NGOs, and some by governments alone.

Top of the list was habitat protection and restoration. Next was extermination of alien pests, particularly rats. New Zealanders, with their vast experience on Pacific Islands where rats pose perhaps the greatest threat, have become the world's experts on "de-ratting". Third on the list was captive breeding and release.

Despite involvement of volunteers and low-paid NGO staff, the bill can be high. The US spends $5m (£2.7m) to $16m a year on certain species, while in Australia, the cost of conserving critically endangered species works out at $5,500 per bird.

These 16 species have had extinction deferred, but they represent just 1.3 per cent of the world's threatened birds. They are also unrepresentative, since 10 are confined to islands, where concentrated action can be effective. More than half of threatened species live on continents, with problems on a larger scale.

Three-quarters, including the parrots, Californian condor, crested ibis, Seychelles magpie-robin and Bali starling, could also be considered "charismatic". Just 48 per cent of all critically endangered birds would qualify. Stuart Butchart, BirdLife's global species programme coordinator, suspects that charismatic species capture conservationists' attention more easily, and are easier to raise funds for.

Mr Butchart emphasises that these 16 species remain on the critical list; they are by no means "saved". The wild population of Bali starling is maintained by release of captive-bred birds, many of which fall into the hands of trappers. But the successes are being sustained. This year a record 11 Chatham Island taikos fledged and flew out to sea, thanks to rigorous rat control. The lessons learned are being successfully applied on dozens of other islands where rats are the main threat to nesting birds.

Mr Butchart says we need to scale up our efforts considerably to prevent many more extinctions in the coming decades. "But these 16 species show that we have the knowledge and tools we need. Future generations will judge us by the number of extinctions we succeed, or fail, in."

The author is director of BirdLife International