Lately, alien species have gained a lot of attention, making headlines for all the wrong reasons. Headlines like ‘Alien species are floating on plastic to the Norwegian shore’, ‘Aggressive blind passengers threaten Norwegian blueberries’, and ‘Unwanted species crossing the boarder threaten Norwegian plants’ are example of headings covering newspapers just in the last year. But what exactly is an alien species, and what makes them so unwanted?

Alien species are species that have been spread to areas where they don’t belong naturally, generally as a result of human activities. Not all alien species pose a threat in the area to which they have been introduced; many of them aren’t even able to reproduce. However, when alien species have the ability to exploit new areas and outcompete native species they become a threat to the local environment, and we call such species invasive. The cane toad (Rhinella marina), zebra mussel (Dreissena polymorpha), Arctic red king crab (Paralithodes camtschaticus), common carp (Cyprinus carpio), black rat (Rattus rattus), wild boar (Sus scrofa), brown trout (Salmo trutta), rabbits (Oryctolagus cuniculus) and Spanish slug (Arion vulgaris) are all well-known examples of invasive species.

Norway classifies these species using the Norwegian Black List. The list is comprised of alien species with either (1) a severe negative effect on Norwegian ecosystems, (2) high dispersal potential and a definite ecological effect, or (3) limited dispersal but strong ecological effect. The list is categorised according to the species’ invasion potential and ecological effect, but it doesn’t necessarily mean they are unwanted or forbidden. There is a separate list of forbidden species made by the government that are illegal to import, sell or release in the Norwegian nature. The Black List is meant as a neutral knowledge foundation. In other words, the blacklist is a tool for governmental decisions regarding conservation, usage and rules. 

This year, a new Black List will be released. So over the next few months, we’ll be posting a series of articles about the Black List’s worst offenders. Who are they? How did they get here? What can we do to stop them? We’ll start next week with the Canadian goose.