The name Hygrocybe obrussea has been used in some countries, but the description of this species is too ambiguous (Boertmann 2010). GBIF (2021) shows some occurrences from North America and Australia. Here these records, and others outside of Europe, are not included, as we suspect that they belong to other taxa.

Hygrocybe quieta mainly occurs in semi-natural grasslands (often calcareous ), and to a lesser degree (probably less than 20% of the population) in rich/calcareous forests (like rich broad-leaved forests and calcareous pine forests), up to subalpine areas. The habitats are declining due to changing agricultural practices, development projects, mining, forestry and pollution. In grassland habitats we assume a habitat loss and population decline of 30-50% over the past 50 years (three generations), probably towards the higher end of the estimate. In forests the habitat loss and population decline could be estimated to be 15-20% over the same period. Over the distribution range we assume an average habitat loss and population decline of more than 30% over the last 50 years. Habitat quality of grasslands has also become impaired and the decline in population size over this time could be even higher because of this, strengthening the assumption of 30-49% population decline. This decline in habitat is ongoing and expected to continue over the next 50 years. GBIF lists more than 4,800 occurrences from Europe (half of them from UK), including duplicates, but due to lacking data in GBIF there could be roughly 6,000-7,000 known localities. Therefore, the species is assumed to have a population of significantly more than 20,000 mature individuals. Overall, the species meets the threshold for listing as Vulnerable under criteria A2ce+3ce+4ce.

Hygrocybe quieta occurs in most parts of Europe, from the lowlands up to subalpine areas (to 2,190 m asl. in the Alps). Eastwards, the distribution limit is uncertain because of a lack of data; in Russia the species is reported from Khabarovsk Krai, Komi Republic, Lipetsk Oblast, Moscow, Novosibirsk Oblast, Primorsky Krai, Tomsk Oblast (Tatiana Svetasheva pers. comm.). GBIF (2021) shows some occurrences from North America and Australia. Here these records are not included, as we suspect that they belong to other taxa. Records from the Far East could be the same as in North America.

GBIF (2024) lists more than 4,800 occurrences from Europe (half of them from UK), including duplicates, but due to lacking data in GBIF there could be roughly 6,000-7,000 known localities. The total number of individuals is unknown, but certainly greatly exceeds 20,000 mature individuals. 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 2006), 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. The habitat quality of seminatural grasslands is also declining, strengthening the population decline. More than 75% of the grasslands habitats are in an unfavourable conservation status (EEA 2021).

In forests the habitat loss and population decline could be estimated to 15-20% over the same 75 year period. Over the whole distribution range we assume a total habitat loss and population decline of at least 30-49% over the last 50 years. As the habitat quality is also declining, the population decline could be higher. Much of the European grasslands have bad habitat quality. This trend is ongoing and expected to continue in the future (Janssen et al. 2016). Hygrocybe quieta is on the Red Lists in at least seven European countries (Mirek et al. 2006, Senn-Irlet et al. 2007, Arnolds and Veerkamp 2008, Dämmrich et al. 2016, Dämon and Krisai-Greilhuber 2017, Artsdatabanken 2021, Moeslund et al. 2023).

Hygrocybe quieta grows in calcareous, mycologically rich but nutrient-poor semi-natural grasslands and to a lesser degree (probably less than20% of the population) in rich/calcareous forests (such as rich broad-leaved forests and calcareous pine forests) or sand dunes (e.g. in Poland). In Norway, the habitat selection has been quantified: N=289 localities; the majority in confirmed semi-natural grasslands, with 69 (14,4%) in rich forests (Jordal et al. 2016). A similar pattern is found in other European countries. It is found from sea level up to subalpine areas in Scandinavia and in the Alps up to 2,190 m asl. The nutrient strategy is unknown, but all "CHEG-fungi" could have some kind of biotrophy or mycorrhiza (Halbwachs et al. 2018). The fruit bodies are short-lived (weeks), but the mycelium is suspected to be longlived; more than 50-100 years.

Habitat destruction and abandonment are the main threats to semi-natural grasslands. The most important process is probably overgrowing due to ceased grazing/mowing of old semi-natural grasslands as part of intensification of agriculture. Further modern cultivation methods use fertilizers, pesticides and ploughing. Also, changed land use with the construction of roads, industrial areas, mining, settlements etc. is impacting forest and grassland sites. Modern forestry practices are also threatening mycologically rich forests. The decline is expected to continue, as at least the areas of semi-natural grasslands are of little economic importance in modern agriculture. Most CHEG grasslands are among habitat types assessed as VU, EN or CR in the EU Red List of habitats (Janssen et al. 2016).

The species is not known to be used.

Hygrocybe quieta is found on the Red Lists in at least eight European countries. The habitats should be protected against destruction for intensification of agriculture or development plans. The maintenance of semi-natural 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 areas of agricultural areas, and should be extended to larger areas than today. Meanwhile, mining and development projects should be avoided. Further ecological research is needed to clarify the nutrient strategy of grassland species and more detailed research on habitat requirements and habitat exploitation by H. quieta would be useful. Additionally, habitat trends should be monitored and management plans are needed.