Richard Mabey: It begins with the bee orchid down our lane

Last summer, at a stroke, the bee orchids went from our lane. Two summers of florid grass growth brought the verge-cutters out early, before the orchids flower and seed, and we won't any longer see those fabulous, chimerical blooms, with their velvet bodies and sculpted pink wings, just an amble away. It's a man-made demise but not the end of the world. There are bee orchids just a mile away, round a patch of dry waste ground used for bike scrambles. They teem around the Mediterranean. I've seen them, with extraordinary opportunist impertinence, poking up on people's lawns.

Yet the neighbourliness of our local patch is something that can't be replaced. For me, settling down in a new habitat in Norfolk, they completed a circle opened up one June day half a lifetime ago, when I saw my first on a picnic in the Chilterns, and knew that I had gone through some subtle graduation in the rites of botany. In a less dramatic way, their passing is like a stitch dropped, part of a great unravelling. But such a local passing will bother only us locals. Bee orchids may be part of that mysterious portmanteau concept "biodiversity" but are not likely to figure on any official Action Plans. They are widespread, unpredictable, and some summers - the final damnation - verge on the common. Government targets, population graphs, earmarked subsidies won't work in situations like this.

The diversity of living forms is what helps the world to survive. It is life's buffer against environmental change, a flush of wild cards. Letting it wither amounts to a collective suicide bid. But it won't "work" if we try to save it as a collection of museum pieces, as isolated "representative" habitats, "back-from-the brink" species, "minimal sustainable populations". A couple of thousand hectares of heathland restored, bittern numbers doubled is a start. But as targets they represent a scenario of despair. Biodiversity does not begin to decline when a species becomes extinct. It starts with the erosion of the common, with the vanishing of a flower from the back lane. It involves the closing-down of personal experiences, the attrition of the most basic elements of intricate, mutually dependent networks.

Shouldn't we be more generous, less dogmatic about what is important, less reliant on endangerment as a trigger for action? What about the truly common species, the backbone of natural - and cultural - systems? What are we doing to safeguard oceanic plankton, and the mycorrhizal fungi on which most trees depend? Shouldn't we be striving to save cowslips, to ensure that the blackbird's song never becomes a folk-memory forever mummified on a compact disc?

We seem to respond to buzz-words, so alongside biodiversity, let us hope for some home-grown bioluxuriance, not just a tabulated series of vegetation types and "typical" creatures gathered into biological ghettos. The one solid argument for the preservation of species is an ethical one: they are important in their own right, as part of the intricacy of life. And for them to be a part of that web means they must flourishthroughout it. That means where we live. If on the way we can enjoy our common inheritance - celebrate the extravagant, superfluous mimicry of the self-pollinating bee orchid - then so much the better.

Richard Mabey is author of 'Flora Britannica'