Some lichen species have undergone population changes in recent decades. Often these are species with a very narrow ecological spectrum (specialists) whose populations are declining, while species that can cope with a wide range of living conditions (generalists) are increasing. This leads to a trivialisation of lichen vegetation and at the same time to a geographical equalisation of species composition. For example, the high nitrogen import in many areas promotes populations of nutrient-loving species, while those species bound to natural forests with a high proportion of old trees and deadwood are declining. The Red List of Endangered Lichen Species in Switzerland provides information on the endangered status of tree and terrestrial lichens in Switzerland.