Nature Studies by Michael McCarthy: Why are some alien invasions welcomed?

A A A

Stick insects are some of the world's most curious and recognisable creatures. They provoke fascination not only for their startling resemblance to sticks or leaves, a perfect piece of evolved camouflage, but also for the sheer anorexic skinniness of many of them; perhaps there is an ancient gene in us that triggers alarm at the sight of anything preternaturally thin.

Officially, stick insects are phasmids; there are more than 3,000 species, mostly in the tropics, and in fact it is a phasmid, the Lord Howe Island stick insect, which is believed to be the rarest invertebrate in the world. It was endemic to Lord Howe Island, isolated in the Pacific nearly 400 miles east of the Australian mainland, until it died out about 80 years ago; but in 2001 a tiny group of the creatures, no more than 30, was found on Ball's Pyramid, an uninhabited and largely lifeless volcanic cone 13 miles away; they are now being captive-bred in Melbourne Zoo.

You would doubtless be surprised to learn that there are British stick insects; but there are. Three New Zealand species have become naturalised in the UK over the past 100 years, all in the South-west: the prickly stick insect, first found in Paignton in 1909; the unarmed stick insect, found in Truro in 1910; and the smooth stick insect, first found in 1949 in Tresco Abbey Gardens on the Isles of Scilly. All are thought to have been brought in by Cornish nurseries importing New Zealand plants; they have survived thanks to the warmth of the South-west winters, and this autumn Buglife, the invertebrate conservation charity, is organising a survey entitled the Great Cornish Stick Insect Hunt to see how they are spreading and how they survived last winter's unusually fierce cold.

Jolly good. No one appears to take exception to the presence of these fascinating aliens from across the world; it seems to be the case that our stick insects are entirely benign, and to discover one in your Cornish privet hedge is merely charming. But what if they were venomous spiders? How would we regard them then? The fact that insects from Down Under can end up flourishing in British gardens only emphasises, in our increasingly globalised society, that the phenomenon of alien or invasive species is likely to become one of increasing concern, as many aliens can have devastating impacts on the ecosystems which they invade.

Take birds. Nearly 200 bird species have gone extinct in the past 500 years; some were lost through over-hunting, like the great auk or the passenger pigeon, but the vast majority were birds of islands, especially flightless ones, which were devastated by the introduction into their ecosystems, by human actions, of foreign species such as rats or cats or snakes. Hawaii has lost 30 per cent of its original bird species, while Guam, the island in the western Pacific, has lost more than 60 per cent of its birds in the past 50 years because of one species, the brown tree snake, accidentally introduced from mainly Asia some time after 1945.

The International Union for Conservation of Nature now regards the introduction of non-native species as the second greatest threat to the world's biodiversity after habitat destruction. But the situation presents us with difficult choices, for often the only way to combat the dire effects of an alien is to extirpate it, assuming that is possible. (There would be little profit in attempting to persuade the brown tree snake to change its behaviour).

And in recent years there has been a growing resistance, at least at the more radical end of society, to humans playing God, as is sometimes said, and taking the decision to wipe out a creature, that other creatures may survive. Now this resistance has gone further, and is morphing into the argument that being prejudiced against creatures which are foreigners is no different to being prejudiced against people who are foreigners and have come to share our society.

In Britain the argument is becoming particularly polarised with regard to the grey squirrel, the American animal introduced in the 19th century which has now driven the more attractive native red squirrel to extinction in most of England (largely through being a carrier of the parapox virus, which is fatal to reds, but harmless to the greys). You can actually see right-left political battle lines being drawn up about Sciurus carolinensis; the fervent wish to extinguish it on the one hand, often with country people, and an angry resistance to the idea on the other, which perhaps has more urban origins.

Countering the effects of invasive species on the natural world is going to be difficult enough in the years to come without politicising it. It is an issue over which we need to be practical rather than judgmental: let's not demonise grey squirrels, which are only doing what comes naturally. Yet there is no denying that their expanding presence in Britain has been of major deleterious consequence for our wildlife, and will continue to be so; ultimately, their presence will entail the red squirrel's entire destruction. Whatever we decide to do about it, we need to be guided by common sense; although that, as Dr Johnson said, is the rarest human virtue.

Fuelling an unwelcome growth in monster nettles

In our front garden in suburban south-west London a stinging nettle is growing which is now about nine feet tall. I didn't notice it at first as it was growing under the beech hedge, until it burst out of the top; it's still growing and doubtless will only be stopped by the frost. Ask me how and why and I will reply: cars. The deposition of nitrogen compounds from millions of car exhausts is increasingly an unwanted fertiliser of the soil, everywhere.

m.mccarthy@independent.co.uk

Suggested Topics
Have you tried new the Independent Digital Edition apps?
Voices
Ed Miliband and David Cameron are neck and neck in the polls
election 2015Armando Iannucci: on how British politics is broken
News
i100
Life and Style
Great minds like Einstein don't think alike
tech
Arts and Entertainment
Billie Piper as Brona in Penny Dreadful
tvReview: It’s business as usual in Victorian London. Let’s hope that changes as we get further into the new series spoiler alert
Life and Style
A nurse tends to a recovering patient on a general ward at The Queen Elizabeth Hospital in Birmingham
health
News
science
Arts and Entertainment
No Offence
tvReview: No Offence has characters who are larger than life and yet somehow completely true to life at the same time spoiler alert
News
Chuck Norris pictured in 1996
people
Arts and Entertainment
Sarah Lucas, I SCREAM DADDIO, Installation View, British Pavilion 2015
artWhy Sarah Lucas is the perfect choice to represent British art at the Venice Biennale
News
A voter placing a ballot paper in the box at a polling station
i100
News
people
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
iJobs Job Widget
iJobs General

Ashdown Group: IT Support Engineer - Leeds

£22000 - £25000 per annum: Ashdown Group: IT Support Engineer - Leeds This i...

SThree: Trainee Recruitment Consultant - Bristol

£18000 - £23000 per annum + Uncapped OTE: SThree: SThree Trainee Recruitment C...

SThree: Trainee Recruitment Consultant - Birmingham

£18000 - £23000 per annum + Uncapped OTE: SThree: SThree Trainee Recruitment C...

SThree: Trainee Recruitment Consultant - Dublin

£13676.46 - £16411.61 per annum + OTE: SThree: SThree Trainee Recruitment Cons...

Day In a Page

General Election 2015: Ed Miliband's unlikely journey from hapless geek to heart-throb

Miliband's unlikely journey from hapless geek to heart-throb

He was meant to be Labour's biggest handicap - but has become almost an asset
General Election 2015: A guide to the smaller parties, from the the National Health Action Party to the Church of the Militant Elvis Party

On the margins

From Militant Elvis to Women's Equality: a guide to the underdogs standing in the election
Amr Darrag: Ex-Muslim Brotherhood minister in exile still believes Egypt's military regime can be replaced with 'moderate' Islamic rule

'This is the battle of young Egypt for the future of our country'

Ex-Muslim Brotherhood minister Amr Darrag still believes the opposition can rid Egypt of its military regime and replace it with 'moderate' Islamic rule, he tells Robert Fisk
Why patients must rely less on doctors: Improving our own health is the 'blockbuster drug of the century'

Why patients must rely less on doctors

Improving our own health is the 'blockbuster drug of the century'
Sarah Lucas is the perfect artist to represent Britain at the Venice Biennale

Flesh in Venice

Sarah Lucas has filled the British pavilion at the Venice Biennale with slinky cats and casts of her female friends' private parts. It makes you proud to be a woman, says Karen Wright
11 best anti-ageing day creams

11 best anti-ageing day creams

Slow down the ageing process with one of these high-performance, hardworking anti-agers
Juventus 2 Real Madrid 1: Five things we learnt, including Iker Casillas is past it and Carlos Tevez remains effective

Juventus vs Real Madrid

Five things we learnt from the Italian's Champions League first leg win over the Spanish giants
Ashes 2015: Test series looks a lost cause for England... whoever takes over as ECB director of cricket

Ashes series looks a lost cause for England...

Whoever takes over as ECB director of cricket, says Stephen Brenkley
Fishing for votes with Nigel Farage: The Ukip leader shows how he can work an audience as he casts his line to the disaffected of Grimsby

Fishing is on Nigel Farage's mind

Ukip leader casts a line to the disaffected
Who is bombing whom in the Middle East? It's amazing they don't all hit each other

Who is bombing whom in the Middle East?

Robert Fisk untangles the countries and factions
China's influence on fashion: At the top of the game both creatively and commercially

China's influence on fashion

At the top of the game both creatively and commercially
Lord O’Donnell: Former cabinet secretary on the election and life away from the levers of power

The man known as GOD has a reputation for getting the job done

Lord O'Donnell's three principles of rule
Rainbow shades: It's all bright on the night

Rainbow shades

It's all bright on the night
'It was first time I had ever tasted chocolate. I kept a piece, and when Amsterdam was liberated, I gave it to the first Allied soldier I saw'

Bread from heaven

Dutch survivors thank RAF for World War II drop that saved millions
Britain will be 'run for the wealthy and powerful' if Tories retain power - Labour

How 'the Axe' helped Labour

UK will be 'run for the wealthy and powerful' if Tories retain power