A pinch of soil: the final frontier

Dinosaurs tried size and failed; we tried intelligence and failed. Now let's see what cockroaches can do

You don't know, in the words of the song, what you've got till it's gone. Or rather, in the case of the number of living things in the world, we don't know what we've got while it's still here. A conservative estimate suggests that 3.5 billion years of evolution have left us with 13 to 14 million species of which 1.75 million have been scientifically described. These figures probably flatter our knowledge. In truth, once we take in bacteria, deep-sea organisms and other exotica, we are left with a living world of which we know next to nothing. As the great scientist E O Wilson has pointed out, any pinch of soil in Amazonia will be teeming with life forms utterly unknown to the most conscientious biologist.

The thought is shocking to a generation brought up to believe that space was the final frontier. Suddenly, we discover, the earth beneath our feet is an alien planet. The shock has created a new anxiety. Extinction is, after all, for ever. David Attenborough and others have long worried us with the thought that the elephant, the panda or some less attractive frogs might go the way of the dodo. But, especially in the case of the panda, this could be dismissed as sentimentality. We feared for their loss because we liked the look of them. But now extinction means something worse, something more intellectually disturbing. It means the loss of biodiversity and that, in due course, will mean the loss of us.

The Global Biodiversity Assessment just published by the United Nations Environment Programme says, in effect, that mankind is in imminent danger of committing indirect suicide. It is doing so by an industrialised assault on the biodiversity of the planet. We are "eroding biological capital" and we may be "on the verge of a further mass extinction spasm". Biodiversity must be preserved. We need a diverse gene pool to support life and protect it against disease, and it is the only sensibly cautious approach - we simply do not know what all those unknown organisms are doing and in what mysteriously benign ways they might be working.

Such scaremongering reports from earnest, global bodies have a bad record. One environmental horror story after another from the late Sixties onwards has been proved wrong or, at least, absurdly premature. According to the most hysterical of these we should, by now, be dead or, at least, devoid of any mineral resources whatsoever. And the activities of Greenpeace - notably over the Brent Spar oil platform - continue to make life easy for the environmental sceptic. If they keep getting their basic science wrong, then what possible authority can they have?

That said, environmentalism remains one of the most powerful new political and social forces in the world today. The sceptic, however rational, cannot compete with what amounts to a global, ethical orthodoxy. Those who are not Green are anti-Green; those who are not saving the planet are destroying it.

The most potent, rational argument for the Green position is prudence. The science of global warming, ozone holes or pollution may not be as solid as the sceptic would wish. But the risks involved are so huge that it makes sense to take certain measures. In the case of biodiversity this argument becomes even more potent. Our ignorance of organic life extends to an even more profound ignorance if how it works. The loss of a bacterium in Amazonia might lead to a plague in Europe. Probably it won't, but a loss of diversity on the scale now being predicted raises the odds.

This sort of awareness is the popular, political expression of an underlying intellectual change that has taken place over the past 40 years. Since the decoding of the structure of the DNA molecule in 1953 and the ensuing explosion in the science of genetics, the sheer power of evolution has become increasingly apparent. "Deep time" - the millennia that have passed since the chemistry of replication first appeared on earth - has been shown to be a staggeringly effective generator of complexity and variety.

DNA has formed the dominant contemporary sense of the world. It is said to be a carrier of information, and information is now what we understand the world to be. The work of biological time is understood as the loading of an immense computer disk with ever more fabulous and improbable combinations of information.

The pervasiveness of the information paradigm has led to a further intellectual insight - the awareness of the connectedness of life. We are all on the same disk. Evolution means that all living things are related - indeed, spectacularly related. Apart from a few RNA bacteria, every organism uses DNA as a genetic messenger. We are cousins to the bug and the virus. When it comes to the primates, we are virtually brothers and sisters. We differ from the chimpanzee only by a marginal 2 per cent of our genetic material.

This is a far more profound shock than any of the other insights of environmentalism. In fact, it might be said to be a reverse of the environmental shock. The Green movement has been based, above all, on our sense of detached sinfulness towards nature. We are apart from nature and our affluence is nature's enemy. But biology seems to show that, whether we like it or not, we are in nature. However alienated our self-consciousness may make us feel, our genes will always reunite us to the living world. In some sense we are incapable of behaving unnaturally. Even if our industrial hubris leads to destruction, this can be seen as part of a natural cycle. Dinosaurs tried size and failed; we tried intelligence and failed. Now let's see what cockroaches can do.

These intellectual changes are now surfacing as a popular programme. Much of the persuasive power of the animal rights movement is based on the sense of the genetic proximity of all living things. And the delicacy and complexity of the biosphere has come to seem increasingly poignant and cherishable when set against the crude destructive power of our technology.

Biodiversity finds its correlative in cultural diversity. The Western democracies might want to rein back their planet-transforming ambitions, but will China, will India, will Brazil with its vastly diverse rainforests? Responses to the well-meaning anxiety of the UN report will be as varied as the bacteria in Wilson's pinch of Amazonian soil.

Equally, the scale of these anxieties will generate fanaticism. The posturing of Greenpeace is one danger. Another is the attempt to impose simple global solutions on local cultures, suppressing local wisdom in the name of a Western liberal ethic.

The worst conclusion to draw from the new biological awareness is that the planet can only be saved if humanity becomes one homogeneous, global mass. The best conclusion would be that our diversity mirrors nature and is just as astonishingly benign.