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.
There is a big word which can be placed in front of many introductions history - Supposed. The pheasant was a cage bird used like hens for meat and eggs by the Romans.There were no records after the Roman period until the Normans. So when the bird became 'wild' has really no date to it. Canada Goose was a gift to James 1st but collared birds have been found here from USA. When an introduction causes £200 million a year in damages to Agriculture, Horticulture and private gardens like the rabbit you would think that species would jump to the front of the cue for being removed. But as its predators are often removed completely by sporting estates then may be the estates should pay the bill. British rail has paid out £ millions over the years for rabbit damage to land owners who blamed the railway land for harboring the rabbit even when all these predators had been removed. One of the best predators was itself classed as an introduction that being the Eagle Owl!
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