Alien species are species that have been spread through human activities to areas where they do not belong naturally. Some of them are a threat to the biodiversity of Norway.
Spreading by human activities
Alien species may originate within Norway, or outside the country. With the aid of human activities, they spread from their natural habitats into regions that they would not be able to reach on their own. The main reasons for the increased spreading of alien species are international business and traveling, and also activities within the Norwegian nature.
Damaging effects are discovered too late
Alien species are not always harmful. In many cases, they live side by side with local species and without any obvious negative effects. Some newcomers, however, pose a threat primarily because they expel the native species and disturb local ecosystems. Alien species may change the Norwegian nature, and also adversely affect industry and public activities in the Norwegian nature.
The damaging effects of alien species are often discovered only when the spreading in nature is advanced. A reversal of the process may then be expensive, difficult or even impossible. To consciously introduce an alien species is always risky, and may have unknown effects on the Norwegian nature.
The work of the Norwegian Biodiversity Information Centre on alien species is organized through a project which also includes other scientific groups. This project is the beginning of a comprehensive and continuous work, where the main goal is to fill the knowledge gaps on alien species in Norway. So far, this work resulted in a national survey of alien species. A “Black List” is being published in the spring of 2007, including lists of alien species that pose a threat to the native biodiversity.