Newcomers – invasive marine plants and animals
Marine species sometimes venture outside their
usual geographic range, finding their way to our shores.
The effect of invasive species
Very few of the non-native species that man
has either directly or indirectly introduced to British waters
become established here. Even fewer threaten the
environment. In fact some newcomers can be beneficial -
a brackish water tubeworm, for example, which actually
improves water quality.
But some invasive species are harmful.
- overwhelm native species by out-competing them - as, for
example, the New Zealand barnacle has done with our native
- bring in new pests, diseases and parasites that affect native
- foul boats, buoys and other structures - as, for
example, the sea squirt, does.
In addition, the seabed can be damaged by fishing for new
How do they get here?
The two main ways are:
- By being carried on ships – on the hulls or in ballast
- Through shellfish cultivation, when species are introduced
deliberately or by accident.
Once species have reached UK waters, they can
still be moved around, either by humans or, if the environment is
suitable for them to breed, by their own spreading powers, as with
the New Zealand barnacle and Japanese wireweed.