The Norwegian Biodiversity Information Centre compiles the Red List of Species in cooperation with a wide range of experts from scientific institutions and individuals with special expertise. The assessments for this edition of the Red List were made by 24 expert committees with a total of 90 members.
Species are assessed against a set of criteria developed by the International Union for Conservation of Nature (IUCN). The criteria and guidelines for using them ensure that assessments are standardised, verifiable and objective. All species are assessed against the following five criteria:
A. Severe reduction in population size
B. Limited geographical range in combination with fragmentation or decline
C. A small declining population and small subpopulations
D. Very small or geographically very restricted population
E. Quantitative analysis
The criteria are used to assign species to one of the categories shown below. The categories reflect the level of risk that a species will die out if conditions remain unchanged. Species in the categories Critically Endangered (CR), Endangered (EN) and Vulnerable (VU) are described as threatened species.