"This provides an objective classification of these species' potential impact on the Norwegian environment. We relied on much of the same principles as are used in the preparation of the 'Red List' of endangered and threatened species," says Professor Bernt-Erik Saether at NTNU's Center for Conservation Biology (CCB), who has spearheaded the development of the new methodology with the help of a coalition of other Norwegian scientists and Biodiversity Information Centre staff.
The method classifies species according to their reproductive ability, growth rate, individual densities, population densities, prevalence and their effect. This information allows the researchers to plot the risks posed by each species on two axes, one which shows the likelihood of the species' dispersal and ability to establish itself in the environment (along with its rate of establishment, if applicable) and the other shows the degree to which the alien species will affect native species and habitats.
Based on the combined values of the two axes, the species can be placed in one of five risk categories:
- Very high risk species that can have a strong negative effect on the Norwegian environment;
- High risk species that have spread widely with some ecological impact, or those that have a major ecological effect but have only limited distribution;
- Potentially high risk species that have very limited dispersal ability, but a substantial ecological impact or vice versa;
- Low risk species, with low or moderate dispersion and moderate to limited ecological effect;
- Species with no known risk factors that are not known to have spread and have no known ecological effects.
Alnes, Godøy (seen from Aksla mountain, Ålesund), Giske municipality, shot by Frode Inge Helland, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license