Clitocybe glareosa is sometimes treated as a member of the genus Infundibulicybe.

Clitocybe glareosa is an endemic European species of semi-natural grasslands which were, for a long time, managed in a traditional way. These habitats are dependent on moderate grazing intensity and/or hand mowing without using artificial fertilisers and pesticides. They are rapidly disappearing worldwide due to changes in land use (agricultural intensification and decline of traditional farming practices) and increased use of fertilisers and pesticides, and as these habitats disappear so do the fungal species that rely on them. This species is easy to recognise and only known from relatively few localities.

The species is not known to occur outside of Europe and it is very rare in all countries where it occurs. The decline in area and quality of available habitat has approached, or possibly exceeded 50% over the last 50 years; and the decline in population size over this time has probably been higher. This decline in habitat is expected to continue even more rapidly over the next 50 years (approximately three generations). Currently the population size is estimated at 1,600-2,000 mature individuals. The species is assessed Endangered because of the small population size (with small subpopulation sizes) that has undergone, and continues to undergo, a significant decline due habitat loss and degradation. This meets the threshold for A2ce+3ce+4ce; C2a(i).

This European species is meridional to boreal in its distribution, preferably occurring in warmer areas with less precipitation. So far, it has been found in France, Italy, Switzerland, Austria, Germany, Hungary, Portugal, Spain, Denmark and the Netherlands, possibly also in Norway, Poland and Sweden. Most records are from Central Europe. The species has very specific habitat requirements.

Clitocybe glareosa is a rare species throughout the range where it is known. GBIF (2024) reports around 80 records, all in Europe. Usually, there are only a few records from each country. Most records are from France, Switzerland and Austria. Only single/few records are from the other countries. It is an easily identifiable species, the number of known localities is 40-50 and the total number, including as yet unknown localities, is estimated to be 10 times more, i.e. up to a maximum of 500. We conservatively estimate the number of different genotypes to be two per locality, on average to correspond to four mature individuals (Dahlberg and Mueller 2011). Hence, then total population size is estimated at 1,600-2,000 mature individuals, with no individual subpopulation containing more than 250 mature individuals. The population is decreasing and Red Listed as Endangered (EN) in the main countries of its occurrence (Switzerland, Austria and Germany), caused by lack of traditional methods of grassland management. This decrease is suspected to be at least 30% over 30 years (past, future and ongoing) but may actually be as high as 50% over three generations (50 years; e.g. 1975-2025) and even higher over longer time-frames.

Clitocybe glareosa grows in mycologically rich but nutrient-poor dry semi-natural grasslands, often on acid soil in grasslands surrounded by heath. Semi-natural grasslands are rapidly disappearing due to changes in land use. Almost all localities of the species are in relatively dry semi-natural grasslands with a few in inland dunes on dry open sandy habitats.

Like other species dependent on semi-natural grasslands, Clitocybe glareosa is threatened by habitat loss due to lack of appropriate management and conversion into higher intensity agricultural lands. The main reasons for decline are agricultural intensification (primarily the application of phosphorus) and the reduction of area and quality of available habitat. In urban and suburban environments, e.g. in Austria at the Perchtoldsorfer Heide, the application of lawn fertilisers, fungicides and moss killers can also affect the species.

According to NATURA 2000 reports (Calaciura and Spinelli 2008), grassland habitats are steadily decreasing, mainly due to abandonment or change in land use. The total area of grassland in the EU fell by an average of 12% between 1975 and 1998, with increases in only very few areas. In areas where the habitat is still present, lack of management results in a continuing decrease in the range of many species due to decrease in habitat quality. According to the Food and Agriculture Organization of the United Nations (FAO), the area of grasslands in the EU declined by 12.8% from 1990 to 2003; only a few Member States managed to avoid this trend (FAO 2006). Pressure caused by land use changes on grassland habitats is steadily increasing. More than 75% of the grassland habitats in the EU are in an unfavourable conservation status, according to draft data provided by Member States under Article 17 of the Habitats Directive.

There is no use and trade known.

This species is included in e.g. the national Red Lists of Austria, Germany and Switzerland as Endangered (Senn-Irlet et al. 2007, Dämmrich et al. 2016, Dämon and Krisai-Greilhuber 2017). Site protection and management of habitats are very important conservation actions for this species. Some grasslands with high species diversity and conservation value are situated within national parks, nature monuments, or nature reserves. However, these grasslands need careful management plans, including grazing which is not always present even within strictly protected areas. This situation results in a continual decrease in habitat quality even if sites are protected from exploitation.

Monitoring of existing localities would be desirable. Population genetics studies on the physical extent of genets (and how many ramets per genet) would improve estimates of the population size.