A report by Scottish Natural Heritage in 2001 found 988 non-native species in Scotland. Most of these currently cause no harm or are beneficial to the economy through their use in agriculture, forestry, horticulture, aquaculture and the pet industry.
However, those that become invasive can cause significant problems to the environment, the economy, health or the way we live. Some of those currently causing problems are listed below.
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American Mink ( Mustela vison)
Many mink escaped or were released from fur farms during the 1930s onwards and have since become widespread across Scotland. They are thought to be a significant factor in the crash of the water vole population, and the huge losses suffered by several seabird colonies on Scottish islands. See more information about this animal in Scotland on the Scottish Natural Heritage Species Action Framework or its ID sheet and fact file on the GB Non-native Species Secretariat Website.
This species is listed on Schedule 9 of the Wildlife and Countryside Act 1981, which makes it illegal to release it into the wild or allow it to escape from captivity.
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Grey Squirrel ( Sciurus carolinensis)
The Grey Squirrel was first introduced during the late 1800s and is now widespread across southern and central Scotland. It is a major pest of forestry because it strips bark from deciduous trees. However it is best known for the catastrophic decline of the red squirrel which it has caused by competing for food and passing on disease.
See more information about this animal on the Scottish Natural Heritage Species Action Framework or its fact file on the GB Non-native Species Secretariat Website.
This species is listed on Schedule 9 of the Wildlife and Countryside Act 1981, which makes it illegal to release into the wild or to allow it to escape from captivity.
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Japanese knotweed ( Fallopia japonica)
Japanese knotweed was originally introduced to Scotland as an ornamental plant in the mid-nineteenth century. It is listed on Schedule 9 of the Wildlife and Countryside Act 1981, which makes it an offence to plant or cause this plant to grow in the wild. It is not an offence if it is growing in your garden or on your land and there is no specific duty either to notify anyone of its presence or to control it (unless doing so forms part of a legally binding contract or agreement with another party).
Japanese knotweed is able to regenerate from very small pieces of plant (fingernail size) and its rhizome system can be up to 3 metres deep, making it extremely difficult to eradicate once established. It is easily spread to new sites through illegal fly-tipping or the careless disposal of "infected" soil and as a result of natural processes such as flooding and erosion. Japanese knotweed causes ecological problems as a result of out-competing native plants. It can also be commercially damaging because of the cost of eradication on development sites and its ability to damage structures and road surfaces.
See this plant's ID sheet on the GB Non-native Species Secretariat Website. Business Gateway also provide advice (developed with NetRegs) and links to guidance on on how to identify and control Japanese knotweed.
The Tweed Invasives Project is a long-term catchment-scale project to control giant hogweed and Japanese knotweed across the Tweed catchment. The Scottish Government provided funding for the production of a Best Practice Guidance Report on the project. You can view the report on the Tweed Forum website
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Rhododendron ponticum ( Rhododendron ponticum)
Rhododendron ponticum was introduced into Britain in the mid 1700s as an ornamental plant. Since then it has become widespread, particularly in woodland habitats on the west coast of Scotland. Although the flowers give a colourful display, it creates dense thickets and shades out native plants and will eventually come to dominate the habitat, to the total exclusion of virtually all other vegetation. Its root system and leaf litter is also toxic to other plants. As a non-native species it provides few compensating benefits for native birds or animals.
See more information about this plant on the Scottish Natural Heritage Species Action Framework or its ID sheet and fact file on the GB Non-native Species Secretariat website.
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Himalayan Balsam ( Impatiens glandulifera)
This attractive plant is a garden escapee that can be often found along riverbanks. It can outgrow native grasses and other plant species, creating an ecologically-harmful monoculture in which native species are unable to thrive. It is able to project its seed over a radius of up to four metres and spreads readily to new areas. The seeds remain viable for years, making eradication a time-consuming and difficult long-term project.
For more information, see the ID sheet on the GB Non-native Species Secretariat website.
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Giant Hogweed ( Heracleum mantegazzianum)
Another garden escapee, this was introduced into Britain in the late 1800s and can often be found on waste ground and riverbanks. It grows up to 5 metres tall and each flower head produces thousands of seeds that are readily dispersed by wind and water. If sap from the plant gets on to the skin and is then exposed to sunlight, it can blister and cause severe skin irritation. (see here for further details). Children in particular are at risk and there are a number of cases each year of injuries caused by contact with this plant.
See more its ID sheet and fact file on the GB Non-native Species Secretariat website.
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