| In the British countryside, alien species are not always undesirables|
|Imagine this autumn scene: you're off to the woods to hunt for a basket of sweet chestnuts. Across the intervening fields where green spikes of barley already break the earth, you flush pheasants and red-legged partridges as you walk. A trio of hares jinks away, their awkward limbs and fantastical ears all dancing on the horizon. Rabbits bolt for cover every 10 paces, and at one particularly fine old sweet chestnut you're caught in the searchlight beam of a little owl's piercing yellow glare.|
When the bird bounds away it draws your eye to the white scuts of a dozen fallow deer trotting for the anonymity of the deep wood. A few metres more and there is your sweet chestnut harvest scattered over the earth like tiny green sputniks that have just showered down from outer space.
Could you think of a scene more intrinsically rural, more quintessentially English, than this? And if you cannot, think again. All the constituents of that imaginary landscape are there because of us. They are what environmentalists call non-native species. Barley came with our Neolithic forebears; hares and chestnuts were iron age imports; the Normans gave us deer, rabbits and pheasants; the partridges arrived at the time of Charles II; while the owl had to wait for a few sympathetic Victorians to make its entree. Yet all are deeply embedded in our sense of the countryside.
The affections that such plants and animals awaken comment obliquely on the present orthodox environmental position, which disallows the introduction of all non-native species. The release of aliens is even illegal, their presence is invariably condemned and now the price of their invasion has been economically quantified, with a report earlier this week that alien wildlife in Europe wreaks ˆ12bn of damage a year.
There are undoubtedly strong reasons for the current position on aliens. Our introduction of non-native plants and animals has had some devastating consequences. The classic locus for this mayhem is isolated islands, of which Hawaii is the perfect example. Biologically unique, this Pacific archipelago once held perhaps 145 bird species found nowhere else on Earth. Today only 35 still exist, and 24 of those are endangered. Of a grand Hawaiian total of 22,000 animals and plants found in the islands, 4,373 are aliens. Yet the true villains among this invading horde to Hawaii's paradisiacal ecosystem are relatively few. They include domestic pigs, rats, mosquitoes, the avian malaria protozoa and the appropriately named big-headed ant.
The problem with such undeniable evidence of aliens' baleful impact is that it can lead to a kneejerk response to all non-native species. It reinforces a binary moral vision of nature – indigenous/good and alien/bad – that oversimplifies an often complex picture.
My earlier chestnut-hunting scenario makes that case nicely. Who would ever argue now that sweet chestnut trees are undesirable aliens? A wood such as Felbrigg, in Norfolk, owned by the National Trust, where 300-year-old veterans reach out to the heavens with vast gnarled arthritic limbs, is one of the most beautiful woodland environments in the country. Rabbits may have played hell with the Australian outback but they are fundamental to the maintenance and ecology of Britain's lastgrassland environments, cropping the sward with their relentless incisors, creating perfect conditions for ground-nesting birds and maintaining floral diversity.
As for the hare, could we even think of spring arriving at all without that creature's madcap capering antics? Yet there is a mammal that argues more strongly for a nuanced approach to non-native invaders. The Chinese water deer is a primitive labrador-sized species with strange vampire canines that escaped into the East Anglian landscape in the mid-20th century. Exotic though it may sound, this endearing creature with teddy bear's ears is now integral to the Broads environment. Where I live the winter nights are filled with the wild music of its courtship calls. Today this alien mammal population may be fundamental to the species' existence, given the parlous condition of the deer in its native Asian range. Britain's Chinese water deer may yet become its last best hope for survival.
So we should continue to bless the hare as a bringer of spring and learn to love the Chinese water deer as a permanent resident in our midst. Ultimately, though, we should avoid a blanket condemnation of "aliens" and take each case – each non-native species – on its individual merits.