In UK we have imported thousands of non-native species in all kinds of ways e.g. in the soil of pot plants, on food crops, on wood products, escaping animals and deliberate species release.
It is thought that 10 to 15% of these species are detrimental to native plants and organisms, they do this by:
- Preying on native species.
- Out-competing native species for food or other resources.
- Causing or carrying disease.
- Preventing native species from reproducing or killing their young.
- Changing food webs: Invasive species can change the food web in an ecosystem by destroying or replacing native food sources. The invasive species may provide little to no food value for wildlife.
- Decreasing biodiversity: Invasive species can alter the abundance or diversity of species that are important habitat for native wildlife.
- Altering ecosystem conditions: Some invasive species are capable of changing the conditions in an ecosystem, such as changing soil chemistry.
Here are just a few of the culprits:
- Spanish slugs, which have also been nicknamed killer slugs, they feed on vegetation, UK native slugs, dead animals and even each other and can withstand up to 20 slug pellets. These 15cm long monsters have a voracious appetite and can soon clear your garden.
- The American mink which feeds on anything they are big enough to catch. They have decimated the water vole population to 5% of its original total.
- Signal Crayfish - The six-inch-long killing machine has already annihilated the smaller native White Claw crayfish from most of the waterways in the south of England. A voracious predator it will eat almost anything it finds including plants, invertebrates, snails, small fish and fish eggs. The Signal also digs burrows up to three feet long in river banks where each year it lays more than 250 eggs at a time. At a time of increased flooding risk the numbers and size of the burrows is increasingly causing river banks to collapse.
- Japanese Knotweed - With its red stems and deep green leaves, it is a pretty enough plant. But Japanese knotweed's beauty belies the fact it has become the scourge of British homeowners. It grows at a ridiculous rate, is near-impossible to get rid of and has ruined house sales - wiping thousands off property prices.
- Harlequin Ladybird - is a relatively recent introduction into this country. This insect has a huge appetite for greenfly, leaving little for native ladybirds that then starve. Worse still, the harlequin will turn on other ladybirds if their food resource diminishes. The invader will also prey on other types of insects, eating butterfly eggs, caterpillars and lacewing larvae.