Facing the challenge of global depletion means changing our habits

David Nicholson-Lord reports on the emergency on planet earth; In 30 or 40 years the Earth's water, soils, forests and atmosphere will be seriously degraded By 2030 two thirds of the world's population will live in urban areas

Extinction, it is commonly said, is forever, and while this is true, it is probably over-dramatic. Species do not usually vanish in a blaze of publicity: like old actors, they tend to fade away. Scientists may later agree they have disappeared, for good, but by then it will be old news. The rest of the world will murmur its condolences and pass on.

By any objective measure - the earth will be a poorer place three of four decades from now. It will have many fewer species and individual creatures and its life support systems - forests, soils, atmosphere and water - will be much degraded. The cause of this damage - the growth in human population with the highest rate of resource consumption and pollution in history and the strain on species will probably not have been curbed. How much of the damage will we notice and how much will we care?

How people respond will largely determine whether, and when, deterioration can be halted. The omens are not particularly good. First, many are no longer listening. The news, it is said, is too depressing - not "upbeat" enough. Many of us therefore behave as if it did not exist. And second, the opportunities for such ostrich-like behaviour are almost certain to grow.

By 2030 the world will have undergone one of the most radical shifts in history, from rural to urban. Two thirds of its population, then totalling between seven and eight billion, will live in cities. Many of them, particularly in the rich Western nations, may well be able to insulate themselves from the symptoms of increasing global instability.

The chief cause of this is the warming of the earth's atmosphere. Climate change is likely to cause, and is probably already causing, higher temperatures, more storms, flooding and drought, an increase in pests and diseases, a reduction in food supply and severe disruption to plant and animal life. One study of the world's most important nature reserves found that between a half and four fifths would be rendered obsolete, their plant communities stranded by shifting climate zones.

The shape and feel of the planet is also being altered by the continuing loss of habitats, forests, wetlands, coral reefs - and the species that inhabit them. At the end of the last Ice Age well over 50 per cent of the world's land surface was covered with forests, today it is now down to around 6 per cent and shrinking fast. An estimated 20,000 species are destroyed each year. Most of the better-known species - carnivores such as big cats and bears, the apes and monkeys, the so-called "charismatic mega fauna" like rhinos are threatened with extinction, globally or locally.

Much of the threat to habitats and species comes directly from human expansion. But there has also been a more mystifying phenomenon, an across- the-board global decline in wildlife populations. This appears to be rooted in a complex range of causes, from traffic fumes, acid rain, pesticides and synthetic chemicals. The common factor throughout is human agency.

These trends together mean that the wild places and animals that remain in Africa, Asia and South America will be in the next century be increasingly corralled into nature reserves and wildlife parks. Surrounding these semi- natural "islands" will be a sea of agriculture, pastureland or urban sprawl. Yet park status is itself no guarantee of survival. If forecasts from bodies like Washington's Worldwatch Institute are correct, growing food shortages may mean that "environmental refugees" will cast envious eyes on their reserves of land, wood and bushmeat.

This may be a depressing prospect, but it has history on its side: something similar has already happened in the West. And for the newly dominant urban majority of 2030, it may hold no horrors. Westerners, in particular, will be able to buy their way out of food shortages and the backwash of climatic change. As city-dwellers they will enjoy visiting wildlife parks on holiday or at weekends - but relatively few of them will realise what they are missing.

Almost certainly there is an alternative future, one in which more wild places and creatures are saved, but it would involve fundamental changes in Western habits - a conscious adoption of planet-friendly lifestyles, for example, which the Third World might then be tempted to emulate.

In Britain, for instance, we have killed off our major carnivores and are not keen to have them back: the idea of reintroducing the wolf to Scotland has received short shrift. Yet we expect Indian villagers to bear the brunt of "saving the tiger" - a species on the verge of extinction but which, unlike the wolf, killed people. Last year a poll by WWF found that for 95 per cent of people it mattered "a lot" if a species became extinct. The challenge now is to find out whether "a lot" will prove enough.