Alien species: species “on the doorstep”

A species “on the doorstep” is an alien species that is not currently established in Norway, but which is most likely to establish itself here within the next 50 years – they are on the doorstep, knocking.

To characterize an alien species as “on the doorstep”, it must be probable that it can reach Norway within the next 50 years. It is, for example, very likely that a species already existing in one of our neighbouring countries will also be able to spread here. Alternatively, it may be a species that is native elsewhere in the world, but which is very likely to be moved to Norway through human activity – for example as stowaways in ballast water, imported soild, garden plants or food.

Examples of species “on the doorstep” in Norway are the racoon dog, racoon, wild boar, European hare, Argentina ant, harlequin ladybeetle, round goby, signal crayfish, American lobster, swallowwort, and the contagious plant disease fire blight.