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Invasive foreign species pose a threat to the global ecosystem Twelve thousand alien species of animals and plants from other lands have taken up residence in Europe, according to the European Union and as human traffic and trade grow, pandora gold bracelet sale that influx will surely increase.

So, according to the House of Commons environmental audit committee in its latest report on invasive non native species, it is time to do something about it. But does the influx really matter? Isn there an upside, too? In any case, what can be done? Invasion by alien species certainly does matter. Right now, biologists say, the world is in the throes of a mass extinction the seventh in the history of life on Earth; one of the biggest, and by far the fastest. Half of all our fellow species are conservatively estimated to be in imminent danger of extinction, including species such as the elephants of Africa and Asia, which set the tone of entire ecosystems; all the big cats; cost of a pandora bracelet and many, if not most, of the primates. The biggest cause across the board is loss of habitat (though poaching is accounting for many of the more saleable and edible species) but the second biggest, it is estimated, is invasion by alien species. Islands are the most vulnerable and over the past few centuries many worldwide have been virtually wiped clean of their native, typically unique species, by introduced goats and rats and weeds or at least seriously depleted, like Hawaii, which has lost an entire suite of flightless geese and ducks and a host of pandora braclett native plants, thanks in part to pigs imported for food and ants that arrived on goodness knows what. Australia is an island, too, albeit on a continental scale, and some biologists claim that most of its native marsupials are endangered or under threat mostly through predation by European foxes and feral cats, and competition from European rabbits, and of course from sheep and cattle. Britain also has scores of introduced species, some of which do obvious harm to the native species including, if we count the ones that came in a long time ago, the house mouse, the brown rat and the rabbit. In more recent times, the grey squirrel, the mink and the muntjac arrived, plus a host of insects and other invertebrates, as well as plants such as the rhododendron from the Himalayas, which has played havoc with native woodland plants in Wales, and Japanese knotweed, which lays all before it to waste. The coypu was introduced in East Anglia, but later eradicated Some might ask, so what? Who cares if a few species that most people don know are there disappear? Money, is one obvious response. Britain invaders cost us around 2 billion a year. Human security is another, for the net effect of invasion is always to reduce species diversity. One importunate invader can compromise or wipe out dozens of native species like the European wasps in New Zealand that thrive on the honeydew from the native southern beech (Nothofagus), go forth and multiply, then prey on the native insects. Some scientists are relaxed about these wipeouts, but many feel that with too much extinction the whole global ecosystem could collapse, taking large numbers of us with it. The most powerful answer, though, is moral and spiritual. Invasions of foreign species have occurred since life began, but the rate of transfer has risen exponentially in recent centuries, and most of the increase has been caused by humans. This has clearly led to many hundreds of extinctions and our hand in this should surely be seen as a crime against nature. There can be an upside, of course. It made sense to reintroduce the white tailed sea eagle to the western isles of Scotland, and the reintroduction cost pandora bracelet of the European crane and great bustard to south west and southern England is now taking place. Though purists would object, it would not be at all foolish to establish semi wild populations of black rhinoceros in Texas. They are devilish hard to conserve in their native Africa and the rhinoceros family seems to have arisen in North America in the deep past. North America is short of big mammals, since it lost most of them (including its mammoths, mastodons, giant bears and giant wolves) in the Great Pleistocene Extinction, around 10 12,000 years ago. Besides, big, slow species are easy to cull if they get out of hand (and are all too easily wiped out). On the whole, though, humanity conscious attempts to rearrange the world fauna and flora have either failed (which is generally the best result) or proved disastrous. The rabbits, cats, foxes and cane toads now wrecking Australia wildlife, and the Australian possums causing mayhem in New Zealand, were all introduced with intentions that were felt to be good at the time: the rabbits for food, the cats for companionship, the foxes to pursue with view halloo, the toads to kill rats in the sugar cane plantations, and the possums for their fur. In the 19th century, wave after wave of British songbirds were taken to Australia to remind the British migrs of home, and generally to cheer the place up: the squawks of the native parrots and did not please them at all. (Most of the imports perished, some disappearing without trace within minutes of release, although the European blackbird is now among Australia top 20 birds at least in numbers, though not alas in popularity, because gardeners think it messes up their flowerbeds.) The signal crayfish is a North American species now found in UK waters Britain was keen on imports, too: the Zoological Society of London was founded in 1826 in part to seek out foreign animals that could be turned into livestock at home, and Captain Cook had botanists on board (notably Sir Joseph Banks) to find useful and ornamental plants. Many are still with us, not least the now ubiquitous eucalyptus. Deep into the 20th century the madness continued. So it was that the French introduced the giant African land snail Achatina into various South Sea islands to which they laid claim, including Tahiti and Moorea, as food for the natives. Then, when Achatina got out of hand, they introduced the predatory snail Euglandina (some snails are remarkably effective predators, such as whelks). But Achatina proved too much of a handful and the Euglandina turned instead to the small native Partula snails. For some time, London Zoo has been breeding some of the last remaining species of Partula. (It requires skill, but they don take up a lot of room.) At the start of the 20th century, one of the commonest broadleaf trees in the eastern United States was the American chestnut, whose fruits had supported whole civilisations of native Americans for hundreds of years, as well as a host of wild creatures and the first European immigrants. But do gooding foresters decided to introduce Asian chestnuts, which have bigger nuts; and they brought with them a parasitic blight fungus that drove the native trees to virtual extinction in a decade or so a wipe out matched only by the collapse of the passenger pigeon at about the same time (though that was caused by too much hunting). So what is to be done? The EU and the environmental audit committee report recommend a for action which certainly sounds good, and would include a combination of legislation and voluntary restraint. In truth, though, once a species is established it can be almost impossible to eradicate and attempts to do so, as the Euglandina/Partula story demonstrates, tend merely to compound the disaster. There is much wild talk from on high of or even nature talk much loved by gung ho scientists and politicians while ads in farming magazines talk of genetically modified organisms or pesticides. In truth and this is one of the greatest lessons of modern ecology we just don know enough to nature, and never will. Nature is immeasurably complex and full of unknowns of the unknowns variety. By the same token, we cannot hope to control the Pandora box of vagrant species simply by legislation.

Above all, we need a change of attitude to acknowledge our own ignorance and to treat nature with extreme caution and respect. The disasters so far all spring from hubris. We have mistaken our own role in the world and hugely overestimated our own ability to understand.

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