Following a blog on reintroductions how about one on reintroductions' evil twin - introductions?
There is a general rule in biology that about one in 10 non-native translocated species becomes established in its new home - and that then one in 10 of those becomes an economic or conservation problem. Non-native species are one of the prime causes of species' extinction and so carting species around the globe is generally a bad thing (please note - Richard Branson).
Many of the non-native species in the UK were allegedly brought here by the Romans (eg pheasant, rabbit) but others were deliberately or accidentally released by the landed gentry (eg little owl, grey squirrel, muntjac deer and Canada goose). But then there is a long list of species whose origins are unknown but which are here as a result of careless trade across the globe.
This blog has commented on ring-necked parakeets (here, here, here and here), pheasants (here), muntjac deer (here) and grey squirrels (here, here and here) at various times to illustrate the practical and intellectual issues surrounding this subject.
It seems likely that we will face continuing and growing problems with non-native species becoming established in the UK. One of the latest arrivals is the scary creature the killer shrimp. What havoc might this species cause in our waterways? What happened to the New Zealand flatworm that was going to take over our gardens about 15 years ago?
Prevention is better than cure, and far cheaper, but difficult to police and ensure. I just have a feeling that this is a growing problem that we will all have to live with. It won't kill us - but it might finish off a few more native species if we aren't careful. And experience shows, we won't be careful enough.
Animal introductions have caused plenty of problems here and elsewhere in the World but perhaps mention could also be made of plant introductions - the dreaded Japanese Knotweed for example. I have seen some astonishing stands of this plant in the Swansea area in particular (though it's well established everywhere).
I don't know if the 1 in 10 ratio, referred to by Mark, holds for plants or not but there is a massive, legitimate trade in garden plants, mostly non-native, which seems likely to result in the ongoing releasing of new species into the wild at a slow but steady rate. Not to mention the various moths, worms, weevils etc that often hitch a ride with the plants when they are imported.
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