It is the best of books, it is the worst of books. It is a book of hope, it is a book of despair; it is a book of beauty, it is a book of ugliness; it is a book about human folly, it is a book about human wisdom. It is the Rare Birds Yearbook for 2008, published by Birdlife International, and it tells of the planet's 189 most threatened birds.

First savour the sadness.

Carrizal seed-eater: the habitat of the only known population was destroyed by work on the Guri Dam in Venezuela.

Chinese crested tern: breeding colonies off the Shandong coast of Northern China have disappeared, probably because of human settlement. Egg-collecting for food threatens remaining colonies.

Cozumel thrasher: found only on Cozumel Island, Mexico. Vulnerable to introduced snakes and cats; hurricanes have affected the remnant population.

Grenada dove: found only in Grenada. Suffered from introduced cats, rats and mongooses. Habitat mostly destroyed. Now a big resort is planned on the little that's left.

Pink-headed duck: found in Indian wetlands. Population initially reduced by hunting, latterly by forest clearance and drainage of wetland, along with egg-collection and human disturbance.

St Helena plover: found only on St Helena. Changes of land use, recreational off-road driving and introduced cats have caused a serious decline, The most important breeding site now earmarked for a new airport.

Waved albatross: breeds on south Espanola island in the Galápagos.

Long-line fishing is the main threat.

But this is more than a series of sad tales of birds with quaint names. We are talking about the loss of biodiversity: and biodiversity is not just something nice and weird and funky. Biodiversity is the basic mechanism by which the planet works.

How many species can we afford to lose? No one knows, but here's the rivet-popper hypothesis: an aeroplane can lose a rivet and continue to fly. And another, and another. But if the loss continues, there will inevitably come a point when the damn thing falls out of the sky.

But here are some happier tales.

Azores bullfinch: conservation work continues will full support of Portuguese Government.

Gurney's pitta: new populations have been discovered by expeditions to Burma.

Madagascar pochard: a diving duck that was considered extinct. It was rediscovered in 2006, and now conservation efforts are in progress to save the tiny remnant population.

Northern bald ibis: one of the world's most peculiar-looking birds.

Satellite tracking, captive breeding and conservation work across the Middle East are continuing.

Sociable lapwing: a satellite tag located a flock of 3,000 birds, the largest for 100 years.

Sumatran ground-cuckoo: not seen for 100 years, but sighted in two places in the past two years.

Yellow-eared parrot: a recovery continues in Colombia, and includes protected areas, reforestation, nest-boxes and an education campaign.

Moral: the world in is a bad state, and the vital web of biodiversity is being destroyed. But there are people out there trying to stop the destruction, and you can be one of them. Birdlife International would welcome your support.

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