Slightly less than 1500 species have been risk-assessed for mainland Norway and its maritime waters. This comprises both established species and door knocker species. In addition, 12 regionally alien species have been assessed.

The experts have assessed 1473 species for mainland Norway and its maritime waters, of which 283 are door knocker species. Door knocker species are not currently established in Norway, but are presumed to be able to be so within 50 years. The number of assessed species also includes two species which are not established in Norway, but which nonetheless have a negative ecological effect: common vetch Vicia sativa segetalis and spotted wing drosophila (fruit fly) Drosophila suzukii.

In addition, 12 regionally alien species have been assessed. These are species which are native to some parts of Norway but which (after 1800) have been spread by human activity to places in Norway where they do not naturally occur.

Species excluded by the definitions and delimitations

The remaining 1529 species are excluded by the definitions and delimitations and for various reasons have not been risk-assessed. Of these, 1219 species are unlikely to become established in Norway within a 50-year time frame eg. date palm Phoenix dactylifera. Some 39 other species were already established in Norway, with stably reproducing populations, prior to the year 1800 and are therefore not risk-assessed eg. sneezewort Achillea ptarmica. Some 36 "production species" are excluded because they were already in widespread use by the 1700s. This applies to the honey bee Apis mellifera and some older cultivated plants eg. redcurrant Ribes rubrum and flax Linum usitatissimum. 86 species are not assessed because they are no longer considered to be alien. 47 species were excluded because the species do not exist in Norway – they were misidentified or incorrectly mentioned. The results also show that 26 taxa are below the species level and share the status of the parent species. Also included in the 1529 species which are not risk-assessed are more than 70 door knocker species.

For some species, several of the reasons mentioned above will be applicable eg. a production species that was in widespread use in the 1700s will probably also have been established prior to 1800. In the meantime, only one reason is provided for each species. In such cases the experts have mainly prioritised the reasons in the order in which they are mentioned above.

What is a production species?

A production species is used for the production of food, timber, other animal or plant products, and for recreation. Examples include the domestic cow Bos taurus, domestic cat Felis catus and rye Secale cereale. The production area of a species is the defined area which is set aside for the actual production eg. a field, a forest stand, grazing land for livestock, a fish pond, a fish farm, or a private garden. Production species that have been introduced to Norway but were in widespread use in the 1700s, and therefore established prior to the year 1800, are not risk-assessed.