Our hand in the future: what can be done to avert mass extinction on a scale not seen since the age of the dinosaurs.

Last summer I saw an extraordinary sight. A dunnock, a bird about the size of a sparrow, was feeding a young cuckoo which was about eight times as big as itself. European cuckoos lay their eggs in the nests of other species. Each female cuckoo has evolved to exploit a particular species, often laying eggs that bear a striking resemblance to the foster mother's own. When the cuckoo egg hatches, the fledgling ejects any other eggs and young from the nest and then makes as much noise as a whole brood of normal chicks so that the host parents are stimulated to feed it as much as they would several of their own young. Meanwhile the parent cuckoos are making their way back to a comparatively easy life in Africa.

To me nature is a constant source of fascination. There is so much drama, beauty, mystery and diversity. The challenge is: how to keep it that way? A study published in the journal Nature (January 2004) says that as many as half-a-million species of plants and animals could become extinct by 2050 as global warming increases. It would be a mass extinction on a scale not seen since the time when the dinosaurs disappeared.

Some will dismiss the study as alarmist but there is ample evidence that many species are in trouble (see box).

Few species become extinct solely as a direct result of persecution by humankind--the pigeon-like dodo and the huge flightless New Zealand birds called 'moas' are recent exceptions. But we are largely to blame for such indirect threats as habitat loss and degradation; pollution; the introduction of species into places where they don't occur naturally; and climate change. Every plant and creature is part of a complex ecosystem, few of which are well understood and some of which are extremely fragile.

Even well-intentioned efforts can have serious consequences. For instance, cane toads were introduced to Australia from Hawaii in 1935 to control scarab beetles that were damaging sugar cane crops. The toads are large (up to 1.3 kgs) and breed quickly. Females lay 8,000-35,000 eggs at a time and may produce two clutches a year, although only one in about 200 eggs will survive to maturity (which takes a year in tropical areas). The species has now spread through much of northern and eastern Queensland in what one columnist described as 'a plague of near biblical proportions'. The toads are toxic. They poison many native animals which prey on amphibians, eat large numbers of native insects and even poison pets and humans.

Does any of this matter? Certainly the world would be less colourful without the tropical birds and the coral reefs with all their extravagantly coloured fish. But few would mourn the passing of cockroaches.

Biodiversity is important for more than aesthetic reasons. On a purely pragmatic level, the totality of all the Earth's ecosystems--what might be called the worldwide web of life--is mankind's support system. We may like to feel that we are the lords of creation but if, for example, the grasses died out we would not outlive them. We simply don't know how many holes can be punched in the eco-web before it tears and loses the strength to support us in significant numbers.

Also, we do not know what resources we are destroying. Many plants have medicinal uses. The classic case is the rosy periwinkle, found in the tropical forests of Madagascar. Without the drug derived from it, many more children would die from leukaemia. How many benefits may one day be derived from other plants and animals, if they are still available to researchers? Half of all medicines prescribed worldwide are originally derived from wild products. And the US National Cancer Institute has identified over 2,000 tropical rainforest plants with potential to fight cancer.

Medicine is only one of many areas where animals and plants have unknown potentialf benefits. Imagine if rubber trees had been wiped out before their value was known. New animals are still being discovered at a rapid rate. We should not let them die out before we've even classified them.

There is also a moral argument. No generation has the right to deny all future generations the chance to see, wonder at, study, harvest and benefit from the huge range of living species that inhabit the Earth. It would be--and increasingly is--an act of vandalism of unprecedented proportions. We could be denying our children the resources they will need to keep them alive.

The main driving forces behind the despoiling of our planet stem from human failings--apathy, greed and materialism. We want to plunder natural resources without taking the human and environmental costs into account. In August 2002 the BBC reported the closure of a $0.5 billion Brazilian government agency, Sudam, because of corruption. Sudam was set up to fund much needed environmentally sustainable projects across the Amazon. A federal prosecutor reported that every one of some 70 projects investigated had 'problems'. All of them had had resources diverted, varying from 30-100 per cent of their grants.

Earlier this year, another press story reported that Chinese gangs were planning how to exterminate the rhinoceros so that their stockpiles of rhino horn would become more valuable. Fragile environments are put at risk in our rapacious hunt for oil. And whatever the pros and cons of genetically modified crops, it is hard to believe that the love of money is not one of the loudest voices in the debate.

Indignation comes cheaply. It is far harder to take effective action to reverse the dangerous trends that are daily gaining momentum. Yet there are many things that individual people can do, including:

* supporting conservation organizations;

* turning your garden into a nature reserve--the combined area of all Britain's gardens is one million acres, equivalent to the county of Suffolk. Even a small organic garden with plenty of native plant species will support many forms of wildlife. A garden pond adds further value (and interest);

* lobbying for environmentally friendly policies in local and national governments;

* adopting a conservation-friendly lifestyle (by saving energy, recycling, avoiding waste, using renewable resources);

* working for a society that is based less on materialism and more on a global sense of solidarity with other people and the natural environment--and making sure that our own life choices are shaped by our ideals.

Changing the world is a tall order. The alternative may be for humankind, like Tyrannosaurus rex, to become nothing more than a fossil record.

BIODIVERSITY UNDER THREAT

* Newsweek's cover story of 14 July, 2003 asked, 'Are the oceans dying?' In the last 50 years, overfishing has removed nine out of ten large predators such as tuna and cod. In 1992 the Canadian government was forced to impose a moratorium on cod fishing, but in 11 years the fish have not come back. Nobody knows why.

* Zoologists estimate there are 500-600 tigers left in the Sundarbans--a 10,000 square km mangrove forest in the Bay of Bengal--down from about 100,000 at the start of the last century.

* Approximately 4,000 species of exotic plants and 500 exotic animals have established free-living populations in the United States. Nearly 700 are known to cause severe harm to agriculture.

* A fungal disease called 'sudden oak death' which has killed 80 per cent of one oak species in the western US has been found for the first time in several British tree species including beech, and holm oak. There is no known cure for the disease.

* The epitome of urban birds, the house sparrow, is all but extinct in central London.

* Researchers from the US and UK estimate that each year approximately 308,000 cetaceans (whales, porpoises and dolphins) are unintentionally drowned by becoming entangled in fishing gear.

* An official 'audit' of British wildlife in 2003 warned that farming methods and industrial pollution were threatening wild thyme, cowslips and hundreds of other native British plants by raising the levels of nutrients in the soil. Their loss would reduce wild bird populations.

* According to a study in Science, the Amazon forest in Brazil, the world's largest remaining wilderness, could vanish within two decades, largely as a result of the 'Advance Brazil' development programme, which will include new highways, railways, hydroelectric projects and housing in the Amazon basin.

* British botanists say that they are near to achieving their goal of saving the seeds of all UK seed-bearing plants. The Millennium Seed Bank, organized by the Royal Botanic Gardens, Kew, already has the seeds of all but two of the UK's 1,400 native species.

Many more examples can be found at www.massextinction.net