World distribution: The species occurs in Europe, North America, Asia, and New Zealand (Egan 1987, Purvis & James 1992a). In Europe it is widely distributed (see e.g. Ahti 1977b, Barreno 1986, Wirth 1987, Purvis & James 1992a, Faltynowicz 1993, Nimis 1993, Santesson 1993). According to Nimis (1993) it is the most common species in the Cladonia chlorophaea complex in the Mediterranean area. In Fennoscandia it is known from Denmark, Sweden, and Norway (Alstrup & Søchting 1989, Santesson 1993)
Ecology: Results. The substrate (indicated in 4 localities) was sandy soil. The habitat was indicated as maritime (1). Discussion. Cladonia humilis is mainly a species of sandy soil (Tønsberg 1979, Tønsberg & Høiland 1980). The main habitat in Norway appears to be maritime sanddunes. In the sanddune areas of Lista, the species is restricted to the inner and established dunes where it occurs in dune pastures, dune heaths, and fixed Ammophila arenaria dunes. The species occurs in prograding as well as in eroding dune systems. It is not among the earliest colonizers, and absent from the outermost dune systems close to the backshore (Tønsberg & Høiland 1980). On the British Isles, C. humilis occurs mainly on dry or sandy ground, especially on recently disturbed soil on roadsides, sea cliffs and in suburban gardens (Purvis & James 1992a)
Threats: Results. Assumed threat was trampling (1). Discussion. All threats to the dune systems are threats also to the sanddune lichens. Trampling by man and cultivation (including fertilization) of the dunes are considered major threats
Status: One of the localities (1420) was investigated; the species was not found (status uncertain). During an investigation of sanddunes on Lista, 1977-1978, the species was found to be fairly abundant; thalli up to 12 cm in diameter were seen (Tønsberg 1979). The locality in Rogaland is within the Jærstrendene National Park, and the sites on Lista (1593, 2313, 2314) are within flora and fauna preservations with biotope protection
Specimens in other herbaria, litterature, etc.