Both these books are attractively produced and most readable. Both are profoundly depressing. Conservation and Biodiversity is beautifully designed by an artist who knows the value of "white" - blank space as an integral part of design - and is a joy just to look at. But why should Andrew Dobson begin by telling us in his introduction that "At no other time in the world's history have species and natural habitats been destroyed at such a rapid rate"? Perhaps he means at no time in human history has this happened and intends us to overlook mass extinctions such as that which occurred at the end of the Permian, when 95 per cent of the fossil record vanished, or the more recent and well-known mass extinction at the end of the Cretaceous, 65 million years ago, an extinction that made way for the very diversity of which he now writes. But no, reading further, we discover that he contradicts himself and is indeed aware of those mass extinctions. He attributes them to slow climatic changes - five million years in the case of the Permian. I would have thought that period quite long enough for at least some significant species diversity to develop among the survivors.

Dobson is of course entitled to his opinion, but it is remarkable that he does not even mention alternative explanations for catastrophic extinctions that may be masked by tectonic or impact events, not even the iridium anomaly discovered by the late Luis and his geologist son Walter Alvarez in the Bottaccione Gorge in Italy and the now widely accepted asteroid impact hypothesis at the end of the Cretaceous.

He has some interesting points to make about size versus abundance of individuals in species. There cannot be land mammals much larger than modern elephants not only because of over-heating during strenuous activity, as he rightly says, but because of limitations imposed by the massive skeleton structure that would be required to support their tissue. Small or middle-sized mammals seem to do better, as he points out. This goes to such lengths that in the megacity of Madras (population about eight million) in India, where I live, there are several wild mammals and reptiles living commensual with man within the city itself. Squirrels are everywhere, the crepuscular little grey mongoose is a common sight, and a civet whose prominent scent gland between anus and scrotum gave early taxonomists such a headache that they dubbed it Paradoxurus hermaphroditus, is shy, strictly nocturnal and rarely seen, but also widespread. Even giant fruit bats survive in a few city colonies, there are occasional families of itinerant bonnet macaques, while wall lizards and the huge, aggressive rats known as bandicoots are ubiquitous. In the many areas where there are large gardens and trees, snakes such as the rat snake or dhaman, the cobra and the krait are common, while bird life, as everywhere in India, is abundant, unlike the endless forests of New Hampshire and other parts of New England I recently visited that appear almost totally birdless.

It is when we come to the larger most spectacular forms of life that we despair. The Indian tiger seems to have little hope; pockets of the Asian elephant, the black buck - a unique and beautiful little Indian antelope - the slender loris and the lion-tailed macaque exist, where they are found at all, in biological islands with none of the connecting corridors stressed by Dobson as essential to their survival. The continuing relentless population explosion - the population of the Indian Republic alone has trebled in the last 50 years - and the ease with which officials charged with conservation of both animals and trees can be corrupted serves to enhance the gloom of conservationists, at least in South Asia. So what has Dobson to offer to encourage us? Very little beyond a learned account of how fast we are rapidly destroying the diversity of which he writes, and of which he correctly stresses the importance. So many people are deeply concerned with astrology, involving the planets and their position in respect of distant constellations, but have no concern for the far greater importance of the earthworm beneath their feet. There are wise and energetic conservation individuals and organisations, but they are impotent against the relentless tide of the land- and fuel-hungry population, while politicians have long ago noticed that while people have votes, trees and tigers do not.

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Conservation and Biodiversity is brilliantly and richly written, but while emphasising that we can never recover species that have been lost, the book does not "provide an alternative solution to the pessimistic journey from Manhattan to Tikal and Easter Island", as the author hopes. Only another thorough sanitising of the planet could do that. This is an astute and most readable book. Whether it adds significantly to what is already known is another matter.

David Quammen's The Song of the Dodo is written in such a racy, witty style as to make the extinction of species sound a downright merry business. We have heard American creationists explain that the dinosaurs became extinct because they were too big to fit into the Ark, but I had never heard of this applied to kangaroos and suchlike. As Quammen says, "could the bloody things jump that far?" It is easy to poke fun at the more naive biblical legends - but that they are taken seriously by creationists is frightening.

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Quammen's book is a stout volume that makes easy reading but could do with some drastic pruning. Do we really need so much space devoted to a catalogue of academic literature - enough, as he suggests, for a modest pile on his desk to weigh 18 pounds - and a lengthy rubbishing of Darwin in favour of the more obscure but diligent Alfred Wallace? Perhaps that is because Quammen's extensive and vividly described wanderings among Amazonian forests and Malaysian and Indonesian archipelagos match or even surpass those of Wallace himself. All very entertaining perhaps, but when do we get to this dodo business? The ideas that Quammen sets out to explore were first proposed 30 years ago by the two young biologists Robert MacArthur and Edward O. Wilson who asked the apparently naive question as to why kangaroos exist in Australia but not in India, while for tigers the situation is the reverse? Why are lemurs found only on the island of Madagascar but not on the vast African continent, so close by? And why do island ecosystems suffer such a high rate of extinctions? The dodo itself is the best-known emblem of such extinctions, but we are faced now with "island" extinctions on the mainland too - the Asian elephant and other Indian mammals already mentioned are examples.

Quammen has a tendency to write like a tabloid journalist, and devotes much space to subjects already well known: the arrival of the bird-eating snake boiga irregularis on the island of Guam, a species almost as demonic as ourselves he remarks, and the extinction of the innumerable unique species of cichlid on Lake Victoria and other lakes of the great African Rift Valley, due to the human introduction of a highly successful predator, the Nile perch. If you can tolerate such blemishes - and there are many - you are left with a book written by an author of undoubted scholarship and integrity. Somehow he reminded me of New Zealand farms where I saw Robin Hood stood on his head by notices saying "Hunters Welcome" in the hope of getting aid in culling the pestilential deer introduced by Europeans, though the greatest treasures of New Zealand's wildlife, including the giant flightless bird called the moa, had been exterminated centuries before by the Polynesian colonisers known today as the Maoris.

It is when we come to the little known primatologists Patricia C. Writer and Karen Strier (why are so many primatologists female? - hink of Jane Goodall, Diana Fossey) that Quammen has really interesting stories to tell, and when we are given first-hand accounts of the lemurs of Madagascar - strange, lovable creatures that most of them are - his story really begins to take hold. Though he certainly writes like a tabloid journalist, everywhere there is the gleam of a ....first-class scientist and observer struggling to get through. I sympathise with him for having been mugged in Rio, but is a book on the extinction of species the place for a detailed, four-page account of it?

Perhaps the author's last quotation from Wallace is the most pertinent: ". . . should civilised man ever reach these distant lands, and bring moral, intellectual, and physical light into the recesses of these virgin forests, we may be sure that he will so disturb the nicely-balanced relations of organic and inorganic nature as to cause (their) disappearance, and finally (their) extinction . . ." Wallace was lucky not to have lived to see what a gross understatement that has proved to be.

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The Song of the Dodo is a delightful, informative and impressive book. A shrewd editor with a lively pair of scissors might even have made it a great one.

Harry Miller is a writer andfellow of the Zoological Society. He lives in south India.