Peter Marren: The problem is mobility. Insects are stuck to their patch

Personally I blame the dinosaurs. The message these all-time losers embody is that it is dangerous to be big. Looking around at the state of wildlife in Britain, I beg to differ. If it's still dangerous to be big, it's bordering on suicidal to be small.

In the past half-century the fortunes of most large animals have improved. We are shooting and snaring fewer of them. Contrast that with the lot of wild plants and insects. One fifth of our native flora is under threat, according to the latest assessment, and that's before we even get started on global warming. Some 200 species of insect have been declared extinct in the past 50 years. Many more have gone missing. What has gone wrong for the flowers and the beetles? The needs of a beetle are more primitive and easier to satisfy, surely, than, say, an osprey or a polecat. Give a flower its native patch of earth and it should be happy. Shouldn't it?

I think the problem is mobility. Far more than birds and mammals, flowers and insects are much attached to their patch. Some insects probably never move more than a few metres away from their birthplace. Behaviour like this seems to border on a death wish, yet they have served these insects reasonably well for thousands of years. What is different today is that their patch of earth is shrinking dangerously. Many nature reserves in the lowlands are now effectively isolated. They have effectively become islands, fragments of wild in an ocean of sterile cereal and rye-grass fields. Most insects and wild flowers have to stay put. If you look around the world at what happens to the wildlife of small isolated islands, the prognosis is not good. The smaller your patch of earth, the more likely it is that you will, sooner or later, die out.

That is the challenge facing us today. Most resources head straight for the popular species: above all, birds. The RSPB has more than a million members and far more money is poured over a single bird than all the insects (with the possible exception of butterflies) put together. Insects and flowers depend on the crumbs falling from the rich birder's table. But, as the missing 250 beetles would plead, if they could only speak, crumbs are clearly not enough.

Peter Marren is the author of Nature Conservation in the Collins New Naturalist series