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First we had biodiversity, now we have conservation biology. The first term refers to species in their many millions, and how they are disappearing at a rate fit to knock off half of them within the lifetimes of younger readers of The THES; the second refers to our scientific response to biodiversity, how to understand what makes it tick and how to help it keep on ticking.

Let us welcome two books, then, that illuminate the situation for us. The first, by Richard Primack, is a popularised version of an academic book published by the author a year ago. He tells us where biodiversity is chiefly to be found, with well over 50 per cent in the tropical rainforests that cover 6 per cent of Earth's land surface. He points out that this is a bug-driven world, and that pollinators are much more important ecologically than are elephants. If we lost half of all vertebrates, that would not be nearly so harmful to the workings of the planetary ecosystem as if we lost half of all invertebrates.

Primack is specially helpful on the economic benefits of biodiversity. He cites notable instances, such as plant-based medicines (anticancer drugs, the contraceptive pill). He might have gone beyond the material goods we derive from biodiversity and made more of the environmental services (pollination, recycling, soil protection, climate regulation, and the like). They are well exemplified by Biosphere II, the man-made technosphere in the Arizona desert that (marginally) regulated life-support systems for eight Biospherians over two years. The cost of the environmental services came to $150 million, or $9 million per person per year. These services are provided to the rest of us by natural processes of biodiversity, at a cost of zero. If we were charged at the rate levied by Biosphere II, the total bill for all Earthospherians would come to $3 quintillion.

Primack also deals with the main threats to biodiversity, such as habitat fragmentation and destruction, grand scale pollution (acid rain), and over-exploitation. Over half the book presents strategies for on-ground conservation. I warmly recommended it.

Primack dedicates his book to his children in the hope that "they will experience the undiminished richness of nature." If only: we are losing dozens of species every day, deserts are expanding and forests are shrinking. When those children first opened their school atlases, they would have noticed a band of brilliant green colour around the equator, denoting the tropical rainforests - the finest celebration of nature ever to grace the face of the planet. When those children's children go to school, they may find the green colouring has had to be replaced by dirty brown or dull grey. Unless, of course, we do a far better job on conservation, which, to his credit, Primack sets out in extended detail.

The second book is more a professional's compendium of our latest knowledge and understanding of habitat management. It is one thing to set aside chunks of land as parks and reserves, it is altogether tougher to maintain the biodiversity originally encompassed. Ecosystems are dynamic affairs, forever changing. They will not simply perpetuate themselves in protected areas, no matter how good the protection. We have to give them a helping hand: to manage them. It is a complicated business, as is demonstrated by this book's 30 authors, including such media luminaries as David Bellamy.

The book ranges across coastal zones, rivers, lakes, fens, reedbeds, grasslands, heaths, woodlands, farmlands and even urban areas, illustrated with specific sites within Britain. Each habitat type is treated with a menu of expert opinions and action options, and a selection of what has worked or gone wrong in the past.

It is a book worth the attention of field ecologists, park wardens, landscape architects, land managers in general, and conservationists of many a stripe. Not unduly technical for the most part, and illustrated with abundant photographs, diagrams and tables.

Some readers might react that wild nature should be preserved as just that - without the meddling hand of humans, however well intentioned. But all our landscapes have become, in some senses at least, human artefacts. If the latter-day conservationist has to pick and chose among kinds of ecosystems, it is because our forebears have picked and chosen on every side. We shall be the better able to select with discretion if we heed the sound science of these two books.

Norman Myers is honorary visiting fellow, Green College, University of Oxford.