10th February 2008, Sunday

… yes we are being invaded by aliens. But the question is can we and should we do anything. Some have the potential to dramatically change our countryside. The matter has cropped up twice this week, at a Workshop of the Rother Catchment organised by the Environment Agency and then in correspondence with the Sussex Biodiversity Record Centre. Today I noticed this alien below, in a new spot at Rye Harbour, it is the Water Fern, Azolla filiculoides.


If you see a red growth on the surface of a ditch it is likely to be this species and it can completely cover the surface and block out the light. However, we have been lucky, this species was introduced to Britain in 1886, as an ornamental pond plant… it is very attractive, and has now spread thought the country. BUT at some stage the weevil, Stenopelmus rufinasus (about 2mm long, with a yellow-striped back) was accidentally introduced and it is an effective biological control of Azolla.

If only there were similar solutions for New Zealand Pigmyweed, Parrot’s-feather, American Mink, Signal Crayfish and many others, perhaps even Canada Geese and Ruddy Duck…