This value points to the tendency of a lichen to occur in areas with different degrees of human disturbance. It is expressed on 4 classes, as follows:
3 = species occurring in heavily disturbed areas, incl. large towns
2 = species occurring in moderately disturbed areas (agricultural areas, small settlements etc.).
1 = species occurring in natural or semi-natural habitats
0 = species which exclusively occur on old trees in ancient, undisturbed forests.
Contrary to the other values, this one has been assigned to epiphytic species only, since it is useful to point out indicators of long ecological continuity of forests.