The purpose of a Red List is to estimate the probability that a species will become extinct within a certain period of time. The species are then classified into categories according to this probability of extinction. The Federal Office for the Environment (FOEN) requires that the evaluation of the endangered status of the individual species comply with the criteria and categories published by the World Conservation Union (IUCN) in 2001.
The first Red List of endangered lichen species in Switzerland was published in 2002. It was drawn up in accordance with the guidelines for the application of the IUCN criteria for regional or national lists.
The Red List of endangered Swiss lichens is currently under revision. The publication of the revised Red List is planned for 2024.