“There’s a deeper problem, too, in our attitude towards aliens. Viewed over millions of years, plants and animals are constantly shifting their distributions over Earth. Just a few thousand years ago, North America was full of camels. Indeed, they evolved there and reached their greatest diversity on that continent. So should camels be regarded as native or alien there today?
Then there is the small-flowered tongue orchid, native to mainland Europe, that first turned up in England in 1989. No one knows whether it arrived by seeds that blew across the English Channel – in which case it’s an endangered native, worthy of nurture – or arrived stuck to someone’s trouser cuff, in which case, says Thompson, ‘it’s just another bloody weed, to be ruthlessly exterminated”. Should how it arrived in the country really make that much difference?'”