Unwelcome Guests?

There is a recent report (http://www.guardian.co.uk/commentisfree/2011/apr/26/invasive-species-killer-shrimps-parrots?INTCMP=SRCH) that the GB Non-native Species Secretariat has targeted a number of 'alien' species for eradication from our borders. These include the 'killer shrimp' (Dikerogammarus villosus) now lurking in Cardiff Bay in the freshwater development as well as the better known examples of the breeding colonies of Ring-necked parakeets (Psittacula krameri) and Monk parakeets (Myiopsitta monachus). One could add to the list species such as the Grey squirrel (Sciurus carolinensis) as well as a whole array of plants including Japanese knotweed and Rhododendron. There are good reasons for attempting to limit the impact of some of these species but the 'black-listing' is somewhat arbitrary. Some species have made their own way to the UK in the fashion of animals and plants that arrived earlier. Other have been inadvertently or deliberately released by gardeners, pet owners and land owners who wanted something a little different (e.g. grey rather than red squirrels). Very little of the UK's flora and fauna can be regarded as pristine. There is a danger that humans attempt to micro-manage environments on the basis of personal preferences or enthusiasms.