Wildlife devastated by globe-trotting invaders

DEEP in the heart of the Yorkshire Dales, a sharp watch is being kept for an exotic - and deadly - invader. Experts fear that an inch-long alien may be quietly spreading through the countryside around the picturesque village of Dent.

The alien, the Asian long-horned beetle - a voracious killer of trees - could be just the latest example of "bio-pollution", which is rapidly becoming one of the most serious and intractable threats to the world's wildlife.

A report, by the Washington-based Worldwatch Institute, says there is an increasing invasion of species into habitats far from their origins, as a result of the growing integration of the world economy.

It estimates that the invasions may cost the world up to pounds 180bn a year and calls for the strengthening of international treaties to combat the problem.

The report describes "the movement of exotic plants and animals into virtually every ecosystem on earth" as a "profound and global challenge to our economic system and conservation skills" and the second greatest cause of extinction on the planet, after loss of habitat to development.

A jellyfish from the Atlantic, it says, has caused the collapse of fisheries in the Black Sea, a Chinese ant is chewing buildings in California, and an Asian mosquito is spreading disease on all five other continents.

The coal black, white polka-dotted beetle, anoplophora glabripennis, arrived in Dent in a wooden pallet containing imported Chinese slate. Neville Allen, a retired maths and science teacher, had ordered the slate for his dining room floor, and later found a strange dead beetle in his home. A succession of experts failed to identify it. Then a week ago, he saw a picture of the same beetle in a newspaper story describing how it was chewing its way through thousands of trees in Chicago after arriving in pallets from China. He raised the alarm and the Forestry Commission went on alert. "The dead beetle could be a one-off, but it's a possibility that others could have escaped," he says. "It's a bit disconcerting. There are a lot of trees around here."

Bio-pollution is as old as travel, but the report, Life Out of Bounds: Bio-invasion in a Borderless World, shows that it has been rapidly increasing in recent decades as growing trade and faster transport shrinks the world. "The global economy," it says, "is merging the world's ecosystems at a frenetic and ever-increasing pace."

Historically it has usually happened through the deliberate introduction of species. The grey squirrel, from North America, originally released in Britain at Woburn Abbey in 1890, has almost ousted the native red squirrel. The Asian muntjac deer, introduced at the same place four years later, also spread and became a pest.

Sixty European starlings were set free in Central Park, New York, also in 1890, by an eccentric American who wanted to populate the New World with every bird mentioned in the works of Shakespeare (the starling appears once in a single line in Henry IV, part 1). Within 50 years they had colonised the entire continent; there are now more than 200 million of them.

The brown trout, introduced for sport fishing, has replaced local species all over North America and Australasia. The ruddy duck, an American bird introduced to Britain by the great naturalist, Sir Peter Scott, is wiping out a native relative.

The brush-tailed possum, brought to New Zealand from Australia 100 years ago in the hopes of establishing a fur industry, escaped, multiplied and developed a voracious appetite for the country's trees. Every night 70 million of them munch their way through many tons of trees as well as eating the eggs and chicks of native birds.

The Nile perch, introduced to Lake Victoria in the 1950s, wiped out 200 local species and destroyed the lake's ecology. And the beautiful water hyacinth, brought to Africa from Latin America by early colonialists to ornament ponds, has blocked out the light and soaked up the oxygen from 90 per cent of the lake's shallows, where fish breed. Large ships get stuck for days at a time in the hyacinths, now regarded as the world's worst tropical weed.

But modern trade and transport has enormously increased the pace and range of bio-pollution. The brown tree snake, which has eaten 12 of Guam's 14 native bird species into extinction, after arriving from Papua New Guinea in military equipment in the 1950s, now turns up at Hawaiian airports, hidden in the wheel wells of planes. Ship containers provide another stowaway place. The Asian tiger mosquito, which can carry at least 18 major diseases, is spreading around the world in little pools of water carried in containers full of used tyres.

But ballast water - a big tanker now carries enough of it to fill 2,000 olympic swimming pools - is perhaps the greatest Trojan horse. It brought a jellyfish, Leidy's comb jelly, from the eastern seaboard of the United States to the Black Sea where it has devastated the fisheries, and is spreading down the Bosphorus to the Mediterranean. The zebra mussel, from the Caspian Sea, plagues the US Great Lakes, where it is remobilising dangerous pollutants from the sediments and putting them back into food chains. A Mediterranean worm carpets Port Phillip Bay, Australia, while a North American one does the same to the Vistula Lagoon in Poland. There are now 30 major alien predators in San Francisco Bay.

The report points out that while the affects of an oil spill lessen over time, "bio-invasions" get worse. "It is smart pollution," says Chris Bright, author of the report. "When an exotic species establishes a beach head, it can proliferate over time and spread to new areas. It can also adapt: it tends to get better and better at exploiting an area's resources and suppressing native species."

As well as the strengthening of international treaties, the report is calling for the redesign of ship ballasts and other "Trojan horses", and an end to the introduction of species.

But the recommendation comes too late for Britain's most endangered species. A study conducted by Bristol University scientists concludes that the invading brown rat has nearly wiped out the black rat, of which just 1,000 remain in the British Isles. Few people mourn the demise of the black version, however: it was responsible for introducing bubonic plague.