Science: Some creatures should stay at home

What's the second biggest threat to the planet? Man introducing rampant species to new parts of the world.

They are alien invaders without any rights of abode. They are more successful, more vigorous and ultimately more deadly than their native cousins. And they are now the second most important reason why the world is losing species at an unprecedented rate. The problem of alien animals and plants - introduced by humans to parts of the globe where they would never normally go - has become one of the most important causes of the crisis in biodiversity at the end of the 20th century.

One scientist has likened the biological era we are living through as the ``Homogecene''. The rich biodiversity of the Earth is being homogenised by the movement and replacement of animals and plants from one area into another. As they become established, they quickly decimate the native flora and fauna. In simple Darwinian terms, it is the survival of the fittest.

Professor Morris Gosling, a mammalian ecologist at the Zoological Society of London, explained what is at stake at last week's British Association science festival in Cardiff: ``The natural world is the end product of a complex and wonderful process of evolution and that has produced a rich biodiversity. What's happening is that we are replacing that biodiversity with a smaller number of invading species.'' The haphazard introduction of non-native species is now running a close second to the destruction of wildlife habitats as the primary cause of species extinction, he added.

Sometimes the introductions are accidental, sometimes deliberate. Occasionally, a species is brought in to destroy a pest but becomes a pest itself. Some aliens eat the native residents, others bring nasty diseases with them. A few - notably the ruddy duck - are just too sexually vigorous. But what they all have in common is that they do not fit in to stable ecosystems, evolved for hundreds of thousands of years without them.

``The rate of invasion is directly correlated with the movement of people around the planet,'' Professor Gosling said. As people move from one place to another, then so do other living things that hitch a ride. Between 1985 and 1996, American customs officials intercepted about 5,600 different species of insect pests on freight destined to be imported into the US. Ships also carry large numbers of aliens from one part of the world to another. ``Ships take on water as ballast, go to another part of the world and just expel it,'' Professor Gosling said.

Ballast water contains eggs and microscopic organisms. One of the earliest examples of this ship-borne invasion stems back to the 1860s when ships coming from American waters expelled their ballast water into the Mediterranean and unwittingly introduced a deadly fungus which has decimated the native crayfish population.

To make matters worse, the American signal crayfish (which was immune to the fungus) was introduced to replace its European cousin. In the 1970s, with government blessing, fish farmers in Britain were encouraged to cultivate the American crayfish, but it soon became a rampaging menace. ``It not only kills the native crayfish. It also destroys the freshwater environment because it eats anything else it comes into contact with. It also burrows into river banks and destroys them in the process,'' said David Holditch of Nottingham University.

One of the best-known examples of a species that is totally inappropriate for anywhere but its native homeland is the American mink. Nobody knows the true numbers of introduced mink in Britain but the experts believe its presence poses a genuine threat to virtually every small mammal and bird it comes across, most notably the British water vole.

David MacDonald, a specialist on the American mink at Oxford University, said: ``They are such an amazingly vigorous and competitive species. They are a triumph of adaptability, being one of the most successful mammalian carnivores.'' Unfortunately, this does not help the British water vole, which has adapted to running away from predators that could neither swim nor fit into its narrow burrow. American mink can do both.

American mink first escaped into Britain from fur farms in the 1920s and since then have established a formidable beachhead for a complete invasion of the countryside. Their destructive influence has, however, become far worse in recent years due to the continued loss of wild habitats.

``The impact of the mink on native species may have been exacerbated by generally disadvantageous things. The habitat bordering our rivers has been eroded to a tiny little ribbon in which everything is confined: everything is dangling on this little tightrope. The mink simply travels along it and bangs off the native prey,'' Dr MacDonald said.

Aggressive carnivores are not the only problem facing the beleaguered scientists trying to fend off the invasion force of non-native species. Hedgehogs are perhaps the most docile animals imaginable yet they are helping to wipe out important colonies of ground-nesting seabirds living on the remote islands of the Outer Hebrides. In the 1970s, just seven were introduced by well-meaning residents as garden pets. Nearly 30 years later, they have expanded to an estimated population of 10,000.

Digger Jackson of the Royal Society for the Protection of Birds said that seabird populations have declined by up to 70 per cent since the hedgehogs arrived, the spiny creatures eating the eggs. The hedgehog population, meanwhile, is aided by fewer predators (and even fewer cars) than on the mainland. They have also formed an unholy alliance with another invader, the rabbit, which conveniently digs the holes in which the hedgehogs live.

Trying to tackle the growth of an alien species frequently means introducing another species to attack them. Most of these work, according to Sean Murphy of CABI bioscience, a consultancy specialising in the biological control of pests. ``The record is that there have been more than 5,000 introductions of agents against insect pests worldwide and 1,000 introductions against weed pests worldwide, and that record has been extremely good now there is an international code for the introductions of biological control agents.''

This has not always been the case, however. One of the worst examples is the introduction of a predatory snail called Euglandina into the Polynesian islands, which were threatened with being overrun by another introduced species, the giant African snail. Unfortunately, Euglandina ignored the African snail and made straight for the native Partula snails. The 117 different species of Partula are now under threat of being wiped out. ``The snail story is a bad example of biological control,'' Dr Murphy said.

Each example of alien invasion requires its own unique remedy. Morris Gosling believes, for instance, that it is possible to eradicate American mink, providing someone is prepared to pay the estimated cost of pounds 30 million. Professor Gosling, who spearheaded the successful eradication of the coypu from East Anglia in the 1980s, said the political will to act is critical to the success of dealing with the growing problem of aliens from abroad. Above all, it is important to provide incentives to those engaged in the eradication programmes. As he says: ``There is the central paradox in pest control: pest control organisations don't stay in business by eradicating the pests.''

Arts and Entertainment

Listen to his collaboration with Naughty Boy

music
Arts and Entertainment
Daniel Craig in a scene from ‘Spectre’, released in the UK on 23 October

film
Arts and Entertainment
Cassetteboy's latest video is called Emperor's New Clothes rap

film
Arts and Entertainment

Poldark review
Arts and Entertainment
Jess Glynne is UK number 1

music

Have you tried new the Independent Digital Edition apps?
Arts and Entertainment

ebooksNow available in paperback
Arts and Entertainment

ebooks
Arts and Entertainment
TV
Arts and Entertainment
Katie Brayben is nominated for Best Actress in a Musical for her role as Carole King in Beautiful

film
Arts and Entertainment
Israeli-born actress Gal Gadot has been cast to play Wonder Woman
film
News
Top Gear presenter James May appears to be struggling with his new-found free time
people
Arts and Entertainment
Kendrick Lamar at the Made in America Festival in Los Angeles last summer
music
Arts and Entertainment
'Marley & Me' with Jennifer Aniston and Owen Wilson
film
Arts and Entertainment
Jon Hamm (right) and John Slattery in the final series of Mad Men
tv
Arts and Entertainment
theatre
Arts and Entertainment
Place Blanche, Paris, 1961, shot by Christer Strömholm
photographyHow the famous camera transformed photography for ever
Arts and Entertainment
The ‘Westmacott Athlete’
art
Arts and Entertainment
‘The Royals’ – a ‘twisted, soapy take on England’s first family’
tv Some of the characters appear to have clear real-life counterparts
News
Brooks is among a dozen show-business professionals ever to have achieved Egot status
people
Arts and Entertainment
A cut above: Sean Penn is outclassed by Mark Rylance in The Gunman
film review
Arts and Entertainment
arts + ents
Arts and Entertainment
James Franco and Zachary Quinto in I Am Michael

Film review Michael Glatze biopic isn't about a self-hating gay man gone straight

Arts and Entertainment
A scene from the movie 'Get Hard'
tvWill Ferrell’s new film Get Hard receives its first reviews
Arts and Entertainment
Left to right: David Cameron (Mark Dexter), Nick Clegg (Bertie Carvel) and Gordon Brown (Ian Grieve)
tvReview: Ian Grieve gets another chance to play Gordon Brown... this is the kinder version
Arts and Entertainment
Benedict Cumberbatch and Martin Freeman in the first look picture from next year's Sherlock special

TV
Arts and Entertainment
Because it wouldn’t be Glastonbury without people kicking off about the headline acts, a petition has already been launched to stop Kanye West performing on the Saturday night

music
Arts and Entertainment
Molly Risker, Helen Monks, Caden-Ellis Wall, Rebekah Staton, Erin Freeman, Philip Jackson and Alexa Davies in ‘Raised by Wolves’

TV review
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?

ES Rentals

    Independent Dating
    and  

    By clicking 'Search' you
    are agreeing to our
    Terms of Use.

    No postcode? No vote

    Floating voters

    How living on a houseboat meant I didn't officially 'exist'
    Louis Theroux's affable Englishman routine begins to wear thin

    By Reason of Insanity

    Louis Theroux's affable Englishman routine begins to wear thin
    Power dressing is back – but no shoulderpads!

    Power dressing is back

    But banish all thoughts of Eighties shoulderpads
    Spanish stone-age cave paintings 'under threat' after being re-opened to the public

    Spanish stone-age cave paintings in Altamira 'under threat'

    Caves were re-opened to the public
    'I was the bookies’ favourite to be first to leave the Cabinet'

    Vince Cable interview

    'I was the bookies’ favourite to be first to leave the Cabinet'
    Election 2015: How many of the Government's coalition agreement promises have been kept?

    Promises, promises

    But how many coalition agreement pledges have been kept?
    The Gaza fisherman who built his own reef - and was shot dead there by an Israeli gunboat

    The death of a Gaza fisherman

    He built his own reef, and was fatally shot there by an Israeli gunboat
    Saudi Arabia's airstrikes in Yemen are fuelling the Gulf's fire

    Saudi airstrikes are fuelling the Gulf's fire

    Arab intervention in Yemen risks entrenching Sunni-Shia divide and handing a victory to Isis, says Patrick Cockburn
    Zayn Malik's departure from One Direction shows the perils of fame in the age of social media

    The only direction Zayn could go

    We wince at the anguish of One Direction's fans, but Malik's departure shows the perils of fame in the age of social media
    Young Magician of the Year 2015: Meet the schoolgirl from Newcastle who has her heart set on being the competition's first female winner

    Spells like teen spirit

    A 16-year-old from Newcastle has set her heart on being the first female to win Young Magician of the Year. Jonathan Owen meets her
    Jonathan Anderson: If fashion is a cycle, this young man knows just how to ride it

    If fashion is a cycle, this young man knows just how to ride it

    British designer Jonathan Anderson is putting his stamp on venerable house Loewe
    Number plates scheme could provide a licence to offend in the land of the free

    Licence to offend in the land of the free

    Cash-strapped states have hit on a way of making money out of drivers that may be in collision with the First Amendment, says Rupert Cornwell
    From farm to fork: Meet the Cornish fishermen, vegetable-growers and butchers causing a stir in London's top restaurants

    From farm to fork in Cornwall

    One man is bringing together Cornwall's most accomplished growers, fishermen and butchers with London's best chefs to put the finest, freshest produce on the plates of some of the country’s best restaurants
    Robert Parker interview: The world's top wine critic on tasting 10,000 bottles a year, absurd drinking notes and New World wannabes

    Robert Parker interview

    The world's top wine critic on tasting 10,000 bottles a year, absurd drinking notes and New World wannabes
    Don't believe the stereotype - or should you?

    Don't believe the stereotype - or should you?

    We exaggerate regional traits and turn them into jokes - and those on the receiving end are in on it too, says DJ Taylor