Alien-The last places on Earth with no invasive species

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The sea lamprey, an invasive species in the Great Lakes, where it feeds on the blood of fish (SPL)
The sea lamprey, an invasive species in the Great Lakes, where it feeds on the blood of fish (SPL)
The sea lamprey, an invasive species in the Great Lakes, where it feeds on the blood of fish (SPL)

When Piero Genovesi received my email, his interest was piqued. Is there anywhere left, I asked, free from invasive species? Genovesi chairs the Invasive Species Specialist Group at the International Union for Conservation of Nature, so he spends much of his time fretting about animal alien invaders. Whether it’s voracious cane toads or pesky squirrels, these creatures cause havoc by invading a place they don’t belong, outcompeting other animals, eating up resources and becoming pests.

So, if there are any pristine ecosystems remaining, where would they be? “This is not an easy question, and one I’ve never asked myself,” Genovesi says. Still, he was intrigued enough to investigate.

The reason it’s a tricky question is because invaded lands vastly outnumber the places still untouched. Where humans go, invasive species tend to follow, Genovesi says, and “there is literally no island in the world that has had no contact with humans in the last century”.

We’ve taxied invasive species around the globe for millennia. Some of the earliest mammal invasions occurred 8,000 to 9,000 years ago, when Neolithic humans introduced wild boars to Sicily and shrews to Cyprus, Sardinia and the Balearic Islands. In AD77, Pliny the Elder penned the oldest written evidence of invasive species’ impacts, writing in his Naturalis Historia that rabbits were causing famines on the Balearic Islands, which forced desperate residents to start throwing ferrets into the rabbit burrows as a means of controlling those insatiable pests.

Passenger aliens

Far from something confined to history, however, detrimental species introductions continue to happen frequently today, from egg-hungry Argentine black and white tegus taking up residence in Florida, to a sudden influx of exotic crazy ants in Texas. Invasive species have been implicated in more than half of recent extinctions and they ring up more than $120bn in annual damages in the US alone.

Some of these stowaways are inadvertent passengers – the rats, roaches and other pests that we ourselves cannot manage to contain. Others are intentionally introduced, whether for food, as pets or in an ill-devised attempt to control another species that we want to get rid of.

Despite their ubiquity, however, Genovesi figured that places free from invasive species must exist, even if he was not aware of them himself. So he submitted the question to the “Aliens-list,” a professional listserve whose 1,000-plus members make up the world’s invasive species management frontline. Putting their collective knowledge to use, they came up with a few examples of places that are most likely free of invasive species.t could we reverse the tide of these pests?
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When Piero Genovesi received my email, his interest was piqued. Is there anywhere left, I asked, free from invasive species? Genovesi chairs the Invasive Species Specialist Group at the International Union for Conservation of Nature, so he spends much of his time fretting about animal alien invaders. Whether it’s voracious cane toads or pesky squirrels, these creatures cause havoc by invading a place they don’t belong, outcompeting other animals, eating up resources and becoming pests.

So, if there are any pristine ecosystems remaining, where would they be? “This is not an easy question, and one I’ve never asked myself,” Genovesi says. Still, he was intrigued enough to investigate.

The reason it’s a tricky question is because invaded lands vastly outnumber the places still untouched. Where humans go, invasive species tend to follow, Genovesi says, and “there is literally no island in the world that has had no contact with humans in the last century”.

We’ve taxied invasive species around the globe for millennia. Some of the earliest mammal invasions occurred 8,000 to 9,000 years ago, when Neolithic humans introduced wild boars to Sicily and shrews to Cyprus, Sardinia and the Balearic Islands. In AD77, Pliny the Elder penned the oldest written evidence of invasive species’ impacts, writing in his Naturalis Historia that rabbits were causing famines on the Balearic Islands, which forced desperate residents to start throwing ferrets into the rabbit burrows as a means of controlling those insatiable pests.

Passenger aliens

Far from something confined to history, however, detrimental species introductions continue to happen frequently today, from egg-hungry Argentine black and white tegus taking up residence in Florida, to a sudden influx of exotic crazy ants in Texas. Invasive species have been implicated in more than half of recent extinctions and they ring up more than $120bn in annual damages in the US alone.

Some of these stowaways are inadvertent passengers – the rats, roaches and other pests that we ourselves cannot manage to contain. Others are intentionally introduced, whether for food, as pets or in an ill-devised attempt to control another species that we want to get rid of.

Despite their ubiquity, however, Genovesi figured that places free from invasive species must exist, even if he was not aware of them himself. So he submitted the question to the “Aliens-list,” a professional listserve whose 1,000-plus members make up the world’s invasive species management frontline. Putting their collective knowledge to use, they came up with a few examples of places that are most likely free of invasive species.

Deep sea vents – one of the few place without alien species? (SPL)

Not surprisingly, only the most remote and extreme ecosystems have managed to exclude invaders. Thermophilic bacteria – the kinds that flourish in environments subjected to excessive heat – likely live free from invaders. Such spots include the hot springs of Yellowstone and Iceland, the edges of deep sea geothermal vents and some volcanic soil. Extremely dry areas, such as the Arabian Desert, also have few if any non-native species. The open ocean’s pelagic zone – the layer of water located between the surface and the sea floor – is usually alien-free as well, as is the deep sea. Caves also tend to escape invasion, although the fungus that causes the deadly white-nose disease in bats is increasingly turning up in those habitats, especially in the US.

Historically, the polar areas largely escaped the presence of invasive species. But concerns are growing that the situation is already beginning to change thanks to an increasing number of tourists, scientists and adventurers visiting those regions, as well as the lessening extremity of those environments, because of climate change. Researchers in Svalbard, an archipelago located in the Arctic Circle, found more than 1,000 seeds from 53 species of alien plants stuck to the shoes of visitors arriving over a single summer, for example, and dozens of non-native species ranging from moths to flies have been spotted buzzing around research stations in Antarctica. So far, none of the invertebrates seem to have permanently established itself on the Antarctic continent, but scientists fear it’s only a matter of time. The nearby South Georgia Island, for example, has already succumbed to that fate: invasive beetles are chomping their way through native ones, and rats and introduced reindeer threaten seabird populations there.p026btrv

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