My train journey to Birmingham recently was enlivened by the sight of buddleja in full flower – beside the track at station approaches, on wastelands at the edge of towns, and even growing out of walls and sprouting from derelict chimneys. This common shrub, imported from China in the nineteenth century and quickly making its escape from gardens, seemed to me to be an unqualified delight, making its home where nothing else would grow and providing a feast of nectar for butterflies and moths – it’s even nicknamed “the butterfly bush”. So I was dismayed to learn that it’s regarded as an invasive species and costs the railway authorities dear in damage to tracks, walls and buildings. Apparently we should deadhead our garden plants immediately to prevent it spreading further; so it’s out with the secateurs for me, as I can’t bear to part with this wildlife resource.
Such alien species are much in my mind at present and the matter is not as simple as might at first appear. Roadsides and riversides are currently choked with Himalayan balsam – another garden escape, handsome and nectar-rich, but eroding riverbanks and screening out native plants, thus seriously damaging biodiversity. It’s hugely successful too. Each plant produces around 800 seeds and efficiently disperses them from its explosive seedpods (one nickname is jumping Jack) using river and stream systems to hitch a ride. Yet many other exotic garden escapees seem to find a niche in the wild and happily co-exist with native flora – no problem.
It’s the same with animals and birds. Many people are surprised to hear that the brown hare is an incomer – brought by the Romans. The little owl – a much more recent import – has found itself a harmless niche and, with its bijou size and mad yellow stare, has given many birdwatchers (me included) a lot of pleasure. Not so, alas, the American mink. Farmed for fur, it escaped – or was released –and spread rapidly, wreaking havoc as it went. An efficient predator both on land and in the water, it kills waterfowl and small mammals and is largely responsible for the near extinction of the water vole. It has to go; they should survive.
Happily, a recent re-introduction project for water voles began last month in Malham with the release of 100 animals. These charming little creatures strim small streamside lawns with orange rodent teeth and deposit their droppings in neat latrines. Let’s hope they survive, thrive and multiply.