It's an inventory of life, but not as we know it

The Variety Of Life By Colin Tudge (Oxford University Press: #35.00) Reviewed by Richard Fortey Gilbert White, one of the world's greatest naturalists, wrote to his friend Daines Barrington on June 2 1778. "Without system the field of nature would be a pathless wilderness," he proclaimed. The system to which White referred was a way of arranging the profusion of species in nature into a classification, to impose a logical arrangement on the animals and plants which engrossed him.

This discipline is still known as systematics. Colin Tudge shares the same mission to define paths through the wilderness. Except that more than 200 years after White roamed the chalky hills around Selborne, Hampshire, the number of species known has multiplied a hundredfold - to say nothing of millions still unknown.

Gilbert White knew virtually nothing of microscopic organisms. Nowadays dozens of kinds of bacteria and single-celled organisms are recognised, each as distinct in its way as animals are from plants.

Even this animal/vegetable divide, the one children learn on their first natural history walk, is as obsolete as the division of the physical world into earth, air, fire and water. The natural world is a whole lot richer than that.

What Colin Tudge has attempted is a new inventory of life, an annotated checklist of everything that now lives, or has ever lived on Earth, all organised according to the latest "system". What could be bolder? Now that species are numbered in many millions, we need a concise guide more than ever. The families of organisms are laid out in logical order, from simple to complex, each one with a good illustration.

What could easily be dull text is always lucid and frequently entertaining. Tudge mourns the loss of systematic education among young biologists, who are more familiar with ribosomes and golgi bodies than with guppies. With this book on the shelf, anyone with natural history leanings can find out what a tardigrade is, or a salp, or when tyrannosaurus lived. Every green-leaning house should have one.

Tudge's lexicon is sandwiched between a clear explanation of how classification is done - he even manages to explain cladistics in a painless fashion - and a postscript which articulates clearly what all naturalists know in their bones: that the diversity of life matters, and that if we exterminate a species it impoverishes us all. The next 100 years will be crucial for the richness of the biology of our planet. Will the world be turned into an endless, dreary "green desert" of food crops to feed our immoderate hordes, or will our great-grandchildren still enjoy the natural profusion which we take for granted?

The omens are not good. We've already killed off thousands of species, and, in places like Indonesia, where the ancient forests are tumbling down to no purpose, others are dying out before they have even been named. This is more than tragedy: it is madness.

So how does Tudge's organismic thesaurus stand the test of a picky critic? I tried out a few creatures I know well, and soon discovered errors. The curious and abundant fossils known as graptolites are not Graptolita (they are Graptolithina).

My own favourite animals, the extinct trilobites, are no longer regarded as any kind of ancestral crustacean or arachnid (spider), as Tudge says, but they are a perfectly good group all of their own, and wonderfully varied. Fungi are treated too shortly and, of those that are there, Cortinarius is the wrong gender, and Cantharellales is misspelled. And there is no such thing as the phylum Endoprocta ... I feel a measure of guilt about being a nit-picker over an endeavour of which I approve so much, but an error in an encyclopaedia is worrying. And if I spotted these in things I do know about, how many more lurk in those I don't?

Perhaps Gilbert White should have the last word. He wrote to another of his correspondents, Thomas Pennant, in 1770, that "no man can alone investigate all the works of nature; partial writers may, each in their department be freer from errors, than more general writers; and so by degrees may pave the way to an universal correct natural history". I fear the universal correct natural history is still some way away, but Colin Tudge has made a useful start: let us hope he is not already too late.

Richard Fortey is visiting professor of palaeobiology at Oxford

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