From plague-harbouring crustaceans, to sprawling superweeds and allergy-inducing insects, invasive species are one of the greatest threats facing biodiversity today.
And they are not only impacting ecology – the economy and human health are suffering too. Invasives are a significant threat to a large proportion of the world’s biodiversity. An alien invasive species is a plant, animal or microorganism that is not native to an area, but has been introduced, either accidentally or deliberately, by humans.
Throughout the week of 13th October the BBC News took a closer look at some of the alien invaders that are in the UK.
While the movement of species around the world is certainly not new, recent horror stories that highlight the damage that some invasive species can cause have made ecologists, politicians and industry sit up and take note.
David Roy, from the Centre for Ecology and Hydrology, has recently co-ordinated the Delivering Alien Invasive Species Inventories for Europe (Daisie) project, which is the most comprehensive inventory of invasive species ever undertaken for Europe. He told BBC News that the number of invasive species had been chronically underestimated.
He said: “We’ve identified almost 11,000 alien species in Europe and the trend of new arrivals is showing no signs of levelling out.”
But while the majority of these are not troublesome, a significant proportion can cause problems. Dr Roy explained: “We found that approximately 15% of the aliens within Europe are known to have some impact on the environment or economy – and this problem goes across all taxonomic groups.”
The problems that alien species can cause are well documented in the UK thanks in many ways to the work of Daisie, the National Biodiversity Network, and its work with the Biological Records Centre
Some have caused the dramatic loss of native flora and fauna – like the catastrophic collapse of the population of red squirrels thanks to the introduction of greys, and the damage caused to ecosystems by species such as the zebra mussel and signal crayfish.
Their impact on the UK economy has also been considerable; the minister for biodiversity recently estimated that invasive species cost the British economy approximately £2bn a year. Programmes to control plants like the Japanese knotweed or floating pennywort, which clogs up rivers causing potential flood risks, are time intensive and expensive.
KEY ALIEN INVADERS
Plants
Rhododendron (ponticum)
Japanese knotweed – see grid map (red)
Himalayan balsam
Giant hogweed
Floating pennywort
Creepy crawlies
Oak processionary moth Rosemary leaf beetle
New Zealand flatworm
Harlequin ladybird
Red lily beetle
Waterlife
Slipper limpet
Signal crayfish
Chinese mitten crab
Zebra mussel
Pacific oyster
Mammals and birds
American mink – see grid map (green)
Grey squirrel
Ring-necked parakeet
Ruddy duck
Muntjac deer
For images of alien species see the ARKive web site