Farm Ireland

Thursday 27 October 2016

We should welcome rather than fear nature's 'invaders'

Ann Fitzgerald

Published 12/08/2015 | 02:30

Alien species: zebra mussels
Alien species: zebra mussels
About 1,000 giant tortoises now inhabit Espanola in the Galapagos Islands

Invasive species such as rhododendron, zebra mussel, Japanese knotweed are evil and we should be making every effort possible to drive them out of country, eh?

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Had I been asked that question a week ago I would have uttered an unambiguous YES.

But having since read a recently published book called The New Wild, Why Invasive Species Will be Nature's Salvation, by Fred Pearce, the situation does not seem so clear-cut.

Taking a colourful journey around the world from the Pacific to the Galapagos Islands, from the Australian outback to urban Britain, Pearce doesn't deny that aliens/non-natives/ invasive have an impact but says the nature of this is often more complex than we may think.

We all like a simple story with good guys and bad guys and the widely-held conservationist view on invasive non-native species is, as quoted by Pearce, that they are "the second greatest threat to biodiversity worldwide after habitat destruction".

Pearce questions the basis of this claim and presents various examples of how non-natives have actually added to biodiversity, with more new species arriving than made extinct, and supported native species.

In Hawaii, alien birds such as the Japanese white-eye and red-billed leiothrix, introduced from India a century ago, are today the mainstay for dispersing the seeds of native shrubs.

What I did not realise because I never thought about it is that non-natives often take hold in an area because the natives are struggling. This, in turn, is because the environment has been altered by our behaviour. Rather than being the problem per se they are a symptom of something more fundamental. They may be "passengers more than drivers."

He relates a story about Lake Victoria where the giant Nile perch were introduced by British colonialists in the 1950s for sport fishing. This was followed by the extermination of around half of the lake's 500 species of small cichlid fish. The perch were blamed but a scientist named Dirk Verschuren suggests the real damage was done by pollution. "Demonising the alien species obscured this," the book states.

Pearce suggests we need to become more creative in our response to these species, "thinking about their vigorous growth as a potentially valuable resource rather than a threat."

In China's Dianchi Lake, invading water hyacinth was harvested and used to produce bio-gas and fertiliser.

He quotes British naturalist Richard Mabey as saying the young shoots of Japanese knotweed make a nice vegetable. "If the rest of us learned to stop fearing it, maybe we could do the same," he says, with studies which show invasives as anything other than irredeemably bad rarely cited.

This guy is no crank. He has been environment and development consultant at New Scientist magazine since 1992 and this book contains hundreds of scientific references.

He, too, used to believe that all non-native arrivals were bad and has written plenty of articles about killer algae but "there was truth in them all, but they missed the bigger picture."


Pearce demonstrates how hard it is to re-engineer even simple ecosystems in a funny-if-it-wasn't -true tale about Macquarie Island, a speck of rock halfway between Australia and Antarctica, which was discovered by Europeans in 1810.

It's literally a cat and mouse chase story which also involves hunters, seals, rats, rabbits, ground-nesting seabirds, conservationists, myxomatosis, more cats, more rats and ever more rabbits.

A final grand plan to eradicate all non-natives involving mass poisoning and a follow-up shooting was finally completed in 2012. Job done? Maybe.

Of course, he is not suggesting that we should throw our hands up in the air and just hand the world over to the aliens. There will always be species that we want to protect. But we need to be clear that we are doing this for cultural reasons, for ourselves, because it is not necessarily something that bothers nature at all.

So what is conservation in the 21st century really about? By trying to hold back the tide, we are slowing evolution.

The world is always changing. Nature is not broken. "Conservation should not be about trying to preserve the past in aspic, still less about trying to recreate the past."

In reality there are no genuine remaining examples of what we imagine to be pristine nature, "the old wild is dead", and instead of trying to recreate ecosystems which we have somewhat arbitrarily decided are ideal, he says we should be "encouraging nature's rebirth, often through the dynamism and invasive instincts of its alien species."

I was disappointed that he didn't or couldn't show an upside to the rhododendron plant that has become widespread but nonetheless, the book left me feeling somewhat liberated.

My mind has been opened to the possibility that the presence of non-native species could be something other than irredeemably bad. Maybe we should divert some of the energy we spend on unwinnable fights into trying to find ways to live with and utilise this "new wild".


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