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Geoglossum difforme Fr.

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Scientific name
Geoglossum difforme
Common names
Klæbrig jordtunge
Klebrige Erdzunge
Veelseptige aardtong
slimy earthtongue
IUCN Specialist Group
Cup-fungi, Truffles and Allies
Assessment status
Assessment date
IUCN Red List Category
Jordal, J.
Ainsworth, A.M. & Mešić, A.

Assessment Notes

The content on this page is fetched from The IUCN Red List of Threatened Species: https://www.iucnredlist.org/species/147297001/147906654


In Europe Geoglossum difforme is very rare and strongly confined to (often acidic) semi-natural grasslands in the lowlands of northern Europe, mainly around the North Sea. Griffith et al. (2013) estimated a habitat loss of 90% over the last 75 years for the CHEG-fungi (grassland fungi of the groups Clavariaceae, Hygrocybe s.l., Entoloma and Geoglossaceae) as a whole in Western Europe (i.e. loss of seminatural grasslands, based on available information). These habitats are declining and getting bad quality due to changing agricultural practices, development projects and pollution (airborne nitrogen deposition). These threats are thought to be most intense in the lowland coastal areas, where this species grows. Habitat quality has also become impaired and the decline in population size over this time could be even higher in Europe. This decline in habitat is ongoing and expected to continue over the next 50 years. In North America the species mainly grows in forests. Habitat trends here are unknown. GBIF lists about 500 occurrences, and about half of these are in North America. The species is assumed to have a population of more than 20,000 mature individuals. In Europe, the habitat loss and population decline is assumed to be >50% in 50 years (past, present and future) (approximately three generations: one generation is assumed to be about 17 years). At a global scale (i.e. Europe + North America) the decline is assumed to be 15-30% taking into account the population reported in North America (GBIF 2019) and the fact that in this area the population may be stable. The species meets the threshold NT (A2c+3c+4c) at the global scale.

Taxonomic notes

G. peckianum is accepted here as a synonym (following Hustad et al. 2013) - this name is used in some European countries (e.g. Germany). The status of GBIF occurrences in North America compared to Europe is uncertain, but for the time being we assume that they are conspecific in accordance with related taxa whose distribution in Europe and North America has been confirmed by DNA. Provisionally, a few occurrences from Japan and New Zealand are regarded as probably related species.

Geographic range

The species is known from Europe, Russia and North America. In Europe it occurs in many countries in the lowland, coastal areas around the North Sea (most important: Scandinavia, UK, Germany, France). In Scandinavia the species is found most often in the southern, coastal parts of Norway, Sweden and Denmark, in the boreonemoral and southern boreal vegetation zone. Distribution data from different continents; North America (e.g. Grund and Harrison 1967, GBIF 2019), Japan (Imai 1941, GBIF 2019) and New Zealand (GBIF 2019) require molecular confirmation. Currently we accept the occurrence in North America, but regard the occurrences in Japan and New Zealand as probably related species, like the situation in some other earth tongues (see e.g. Hustad et al. 2013).

Population and Trends

According to GBIF (2019) there are in total about 500 occurrences, with about half in North America. Based on available information on trends in seminatural grasslands, Griffith et al. (2013) estimated a habitat loss of 90% over the last 75 years for the CHEG-fungi (grassland fungi of Clavariaceae, Hygrocybe s.l., Entoloma and Geoglossaceae) as a whole in Western Europe. According to the Food and Agriculture Organization of the United Nations (FAO), the area of grasslands in the EU declined by 12.8% over 13 years (1990-2003). Also other sources point to a habitat loss in seminatural grasslands of roughly 1% per year in Europe over a longer time, although the data quality is not always very good. Of 22 occurrences in the UK, only 3 are from after 1980 (NBN 2019). A strong decline over 20 years is documented in Sweden (Nitare 1988). In North America the species occurs in forests and the population trend is here poorly known - no decline can be assumed. In the seminatural grasslands of north European coastal lowland we assume a total habitat loss and population decline of >50% over the last 50 years (3 generations lengths). As the habitat quality is also declining (especially in the main habitat – seminatural grasslands in European lowlands), this underlines a high population decline. Over the whole distribution range we assume a total habitat loss and population decline of 15%-30% over the last 50 years. This trend is ongoing and expected to continue in the future.

Population Trend: decreasing

Habitat and Ecology

The European population of Geoglossum difforme grows in mycologically rich but nutrient-poor semi-natural grasslands, often on acid soil in grasslands surrounded by heath. Semi-natural grasslands are rapidly disappearing due to changes in land use (see Threats and Population). In Norway, almost all localities of the species are in semi-natural grasslands and none in forests (Jordal et al. 2016), and similar patterns are found in other countries. In North America, habitat information is sparse; one record is from a wooded ravine in Nova Scotia (Grund and Harrison 1966). The nutrient strategy is unknown but it could have some kind of biotrophy or mycorrhiza, like waxcaps (Nitare 1988).


Habitat destruction and abandonment are the main threats to seminatural grasslands. The most important process is probably overgrowing due to ceased grazing/mowing of old seminatural grasslands as part of intensification of agriculture. Further modern cultivation methods like use of fertilizers, pesticides and ploughing. Also in some places changed land use with the construction of roads, industrial areas, settlements etc. Airborne nitrogen deposition is another significant threat. The decline is expected to continue, as at least the areas of seminatural grasslands are of little economic importance in modern agriculture. Most CHEG grasslands (see Population) are among types assessed as VU, EN or CR in the EU Red List of habitats (Janssen et al. 2016).

Conservation Actions

The habitats should be protected against destruction due to intensification of agriculture or development plans. The maintaining of seminatural grasslands demands yearly grazing or mowing. If grazing by heavy animals destroys part of the soil, light animals like sheep should be recommended. Habitat conservation by governmental support to traditional agricultural practices is most important, this exists in many countries to maintain extensive agricultural areas, and should be extended to larger areas than today. The species is suggested as a priority species in Norway (Jordal 2013).

Further ecological research is needed to clarify the nutrient strategy of grassland fungi. Management plans are needed. Habitat trends should be monitored.

Use and Trade

The species is not known to be used.

Source and Citation

Jordal, J. 2019. Geoglossum difforme. The IUCN Red List of Threatened Species 2019: e.T147297001A147906654. https://dx.doi.org/10.2305/IUCN.UK.2019-2.RLTS.T147297001A147906654.en .Downloaded on 31 January 2021

Country occurrence