Invasion of the Aliens

Foreign marine species are pushing UK natives out. Jonathan Owen reports

British waters are being invaded by a wave of species making their way in from the sea, according to a new study. While foreign varieties of barnacles, brown seaweed and kelp may not sound dramatic, they are, in effect, slipping in under the radar, their progress hastened by climate change, according to Dr Nova Mieszkowska from the Marine Biological Association.

Their arrival will add to pressure on native species already under siege by a range of marine invaders to Britain's shores such as the American red signal crayfish and the Pacific oyster. Some have arrived as a result of climate change, while others have made their way here on ships' hulls, in ballast water or through the global trade in aquaculture.

"All of these alterations to our ecosystems are impacting biodiversity. We are likely to face a loss in native biodiversity as warming forces our species out of many of their habitats," said Dr Mieszkowska, whose research, based on data stretching back more than 50 years, was presented at the First World Conference on Marine Biodiversity in Valencia this month.

"The worst-case scenario is that aliens will continue to arrive and become established, and that we may see a progression towards globalisation of fauna, whereby communities in several remote countries all have a similar list of species instead of the diversity that we see today."

Veined rapa whelk

This mollusc feeds on clams and is already in British waters. It may spread through ballast waters of ships.

Green sea fingers

This Pacific seaweed has been blamed for the decline of native varieties such as velvet horn.

Pacific oyster

First imported for commercial farming in the 1970s, has since escaped into the wild and is displacing native oysters.

Slipper limpet

The rapid growth of this species along Britain's south coast could destroy scallop beds.

American red signal crayfish

Initially bred on farms for the restaurant trade, now a major problem in river systems. It will eat almost anything it can find and burrows into the sides of riverbanks.