Are ‘alien species’ everywhere?

When Piero Genovesi received my email, his interest was piqued. Is there anywhere left, I asked, free from invasive species? Genovesi chairs theInvasive 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 theearliest mammal