Traditionally most conservationists have an aversion to ‘alien invaders’. From Giant Hog Weed to Grey Squirrels, since the begining of the 20th century, these have mostly been persecuted, and in some cases like the Coypu and Musk Rat, extirpated. But not always. Edible Dormice and Little Owls, have been allowed to exist, while Muntjac and Chinese Water Deer are rapidly expanding their range and are probably impossible to exterminate. Meanwhile, other species, once extinct are being reintroduced, such as the Beaver. The fact that the original ecosystems that Beavers once lived in have pretty well disappeared, seems to be considered irrelevant. And some aliens are treated as native, simply because they have been here a long time. Brown Hare and Rabbits, for example. Many species simply did not get here because by 5000 years ago Doggerland had disappeared, and the English Channel was inundated. So Garden Dormice, and Crested Larks, and numerous other species stop 21 miles away from England. But Collared doves, following man-made habitats spread across Europe in the early-20th century, and in the late 1950s managed to hop across the Channel and colonise Britain, and so are ‘natural’. Mandarin ducks were deliberately released, but because they are pretty, allowed to thrive. Ring-necked Parakeets are more controversial, but Ruddy ducks because they were more fecund than the closely related White–tailed Duck (which was declining in Europe) and there were fears about hybridization was subjected to a deliberate (and expensive) extermination campaign. Meanwhile another species is slowly loping across Europe: the Golden Jackal. Once confined to the eastern Mediterranean area, it has now spread across the Alps, and even been recorded in Holland. But with no DoggerLand, it will stop short at the Channel (unless it can run through the tunnel or hitch a ride). And therein is another paradox, If a species hitches a ride (as did Rats and House Mice), they are considered aliens. But, if they can fly, then they are ‘natural’. This of course creates difficulties over the status of Scilly Shrews, and Orkney Voles. Both of which were for a long time thought to be natural colonists, but now considered ship assisted invaders
To me the fundamental problem with all of this, is that it fails to take into account that almost the entire landscape, and almost all habitats in Britain show major anthropogenic changes. A huge part of the flora consists of ‘aliens’. And almost the entire agricultural landscape comprises domesticated alien plants and animals. Surely we should be looking at the potential species diversity of what we currently have, not making futile attempts to recreate an ecosystem that may have existed 5000 or more years ago? Jackals are far more suited to modern Britain than wolves. Stone Martens would thrive far better than Pine Martens, and for that matter, Sciurus hudsonicus, appears to be able to co-exist with Grey Squirrels better than our native Red Squirrels.
Much of what I have written above is of course conservation heresy. But it also illustrates another fact: fashions change, and what is heresy now was once good science…. Food for thought. But what is also clear is that there is nothing rational about conservationists’ attitudes to alien species, at least in Britain. If anyone thinks they could propose a rational strategy I would be fascinated to read it. I write this a props to the current interest in so-called ‘rewilding’ of Britain.