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Love those alien species!
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Learning to love aliens From tongue orchids to camels, non-native species get a bad press, finds Bob Holmes
WE HAVE all heard a lot of bad stuff about introduced species: they run rampant through our ecosystems, costing billions to control each year. They are also accused of driving native species extinct. Indeed, alien species are often cited as one of the big threats to biodiversity. Not so fast. In Where Do Camels Belong? The story and science of invasive species, plant biologist Ken Thompson argues that most alien species – even some topping the eco-horror lists – cause little or no lasting damage and aren’t worth the angst, effort or money we devote to controlling them. Purple loosestrife, for example, is often viewed as one of the worst invasive weeds in North America because it forms dense stands of tall, conspicuous flowering heads. But when ecologists looked closer, reports Thompson, there was little evidence of actual harm. Even in Hawaii – poster child for the noxious effects of alien species – invaders tend to make ecosystems more diverse, not less. Nor are introduced species the financial burden they are often made out to be. For one thing, says Thompson, hardly anyone bothers to count the economic benefits of “aliens” such as wheat and cows – a sum that runs to $800 billion per year in the US alone. Moreover, much of the cost of the invaders turns out to be the Camels evolved in North America, but are now only wild in Australia 54 | NewScientist | 29 March 2014
money spent controlling them. how it arrived in the country There’s a deeper problem, too, really make that much difference? in our attitude towards aliens. Thompson makes his case in a Viewed over millions of years, lively, readable style, spiced with plants and animals are constantly a healthy dose of sarcasm towards shifting their distributions over “aliens = bad” fundamentalists. Earth. Just a few thousand years Better yet, he bolsters his ago, North America was full of argument with plenty of citations camels. Indeed, they evolved from the scientific literature, there and reached their greatest which adds welcome heft. diversity on that continent. Not everyone will find his So should camels be regarded “We may as well let today’s as native or alien there today? alien species and their Then there is the smallecosystems settle down to flowered tongue orchid, native comfortable coexistence” to mainland Europe, that first turned up in England in 1989. No one knows whether it arrived argument convincing, however. by seeds that blew across the When Thompson published English Channel – in which case similar arguments in scientific it’s an endangered native, worthy journals, sceptical opponents of nurture – or arrived stuck to accused him of cherry-picking someone’s trouser cuff, in which examples that fit his argument, case, says Thompson, “it’s just while ignoring contrary evidence. another bloody weed, to be Even if there is any substance ruthlessly exterminated”. Should to that claim, Thompson makes
a worthwhile point. Species aren’t necessarily ecologically harmful just because they are introduced, nor are native species necessarily good for biodiversity: “If bracken were alien [to the UK], it would be seen as no less than a national emergency,” he writes. Instead, Thompson argues, we need to take a more conciliatory attitude and treat each species on its merits. We should still take care to avoid moving species to new places, and fight hard to control those aliens that are truly nasty, such as Australia’s cane toads. But we may as well get used to the rest of today’s aliens, and let them and their ecosystems settle down to comfortable coexistence. After all, he notes, many are doing that already, just as they have done throughout history. n Bob Holmes is a consultant for New Scientist
Peter Walton Photography/getty images
Where Do Camels Belong? The story and science of invasive species by Ken Thompson, Profile Books, £10.99
Learning to love aliens From tongue orchids to camels, non-native species get a bad press, finds Bob Holmes
WE HAVE all heard a lot of bad stuff about introduced species: they run rampant through our ecosystems, costing billions to control each year. They are also accused of driving native species extinct. Indeed, alien species are often cited as one of the big threats to biodiversity. Not so fast. In Where Do Camels Belong? The story and science of invasive species, plant biologist Ken Thompson argues that most alien species – even some topping the eco-horror lists – cause little or no lasting damage and aren’t worth the angst, effort or money we devote to controlling them. Purple loosestrife, for example, is often viewed as one of the worst invasive weeds in North America because it forms dense stands of tall, conspicuous flowering heads. But when ecologists looked closer, reports Thompson, there was little evidence of actual harm. Even in Hawaii – poster child for the noxious effects of alien species – invaders tend to make ecosystems more diverse, not less. Nor are introduced species the financial burden they are often made out to be. For one thing, says Thompson, hardly anyone bothers to count the economic benefits of “aliens” such as wheat and cows – a sum that runs to $800 billion per year in the US alone. Moreover, much of the cost of the invaders turns out to be the Camels evolved in North America, but are now only wild in Australia 54 | NewScientist | 29 March 2014
money spent controlling them. how it arrived in the country There’s a deeper problem, too, really make that much difference? in our attitude towards aliens. Thompson makes his case in a Viewed over millions of years, lively, readable style, spiced with plants and animals are constantly a healthy dose of sarcasm towards shifting their distributions over “aliens = bad” fundamentalists. Earth. Just a few thousand years Better yet, he bolsters his ago, North America was full of argument with plenty of citations camels. Indeed, they evolved from the scientific literature, there and reached their greatest which adds welcome heft. diversity on that continent. Not everyone will find his So should camels be regarded “We may as well let today’s as native or alien there today? alien species and their Then there is the smallecosystems settle down to flowered tongue orchid, native comfortable coexistence” to mainland Europe, that first turned up in England in 1989. No one knows whether it arrived argument convincing, however. by seeds that blew across the When Thompson published English Channel – in which case similar arguments in scientific it’s an endangered native, worthy journals, sceptical opponents of nurture – or arrived stuck to accused him of cherry-picking someone’s trouser cuff, in which examples that fit his argument, case, says Thompson, “it’s just while ignoring contrary evidence. another bloody weed, to be Even if there is any substance ruthlessly exterminated”. Should to that claim, Thompson makes
a worthwhile point. Species aren’t necessarily ecologically harmful just because they are introduced, nor are native species necessarily good for biodiversity: “If bracken were alien [to the UK], it would be seen as no less than a national emergency,” he writes. Instead, Thompson argues, we need to take a more conciliatory attitude and treat each species on its merits. We should still take care to avoid moving species to new places, and fight hard to control those aliens that are truly nasty, such as Australia’s cane toads. But we may as well get used to the rest of today’s aliens, and let them and their ecosystems settle down to comfortable coexistence. After all, he notes, many are doing that already, just as they have done throughout history. n Bob Holmes is a consultant for New Scientist
Peter Walton Photography/getty images
Where Do Camels Belong? The story and science of invasive species by Ken Thompson, Profile Books, £10.99