I've talked before about the problem with alien (non-native) species (particularly Himalayan balsam) in the Uck catchment, and we have now found a number of new stands of Japanese knotweed which is unfortunate. The key to successful eradication of these alien species is early identification and control before it has chance to spread. Japanese knotweed is particularly virulent, with the ability to regenerate from root sections as small as 7mm! This also means that removal should be done with someone who has relevant experience and expertise. If you spot alien species in the catchment please get in touch or log it on this useful website.
It's never been easier to get involved in charting and spotting different species, with a myriad of identification tools such as ispot (you can also get help with identification here) and phone apps, as well as ID books, and a range of practical courses provided by Sussex Wildlife Trust and others. It's also a fun way to spend a day outdoors with the family, and can be enriched by the folklore of different species and the wider countryside. If you want some inspiration take a look at these blogs from SWT ecologist Graeme Lyons and Sussex naturalist Dr Patrick Roper and also the Adastra 2012 review.