Invasive non-native Invertebrate Species

There are more than 3,000 non-native species currently in the UK. A number of these only turn up occasionally and don’t breed here, some are harmless and are unlikely to cause any problems, such as the three species of stick insects that can be found in South-West England.

In fact, only 234 out of more than 3,000 are thought to have a negative impact on our environment or health. But these 234 can cause rampant problems and are often difficult to control. An ecosystem is a delicate balance of species which have lived with each other for millions of years. Carnivores keep herbivores in check, herbivores chomp down on the plant structure within a landscape, add a new species and sometimes that balance can be turned upside down.

Take crayfish, for example. We have at least 6 species of introduced crayfish living in the wild in England with fewer species in Wales and Scotland. Most of these species were brought to provide food or angling bait and they then escaped into the wild. Now, many of these introduced species are having a negative impact on our native White-clawed Crayfish (Austropotamobius pallipes) and our rivers.

Plants can also have an indirect negative impact on our invertebrates. Himalayan Balsam (Impatiens glandulifera) was introduced as a garden plant, but quickly escaped into the wild. It shades out other vegetation and has led to the decline of our native Tansy Plant (Tanacetum vulgare) which is fed upon by the Tansy Beetle (Chrysolina graminis). This beautiful leaf beetle can now only be found along the banks of the River Ouse and in a Cambridgeshire fen.

Control is often difficult. Many of the aquatic organisms are transported through ballast water on ships and require treatment. Terrestrial invertebrates are brought in by trees and pot plants. Some are brought in for pollination, but then run the risk of escaping and spreading diseases.

New European Union regulations are came into effect on the 1st January 2015. Part of this was a recommendation that member states create lists of invasive alien species of concern, and put appropriate control measures in place. With this in mind, Buglife has defined a process for identifying the species by assessing ‘at risk’ invasive species which are likely to cause the most damage to our environment.