Assessment Notes

Justification

Hygrocybe spadicea is a well-characterized waxcap with a brown, conical to umbonate pileus, contrasting with the yellow, stipe and lamellae (sometimes white in var. albifolia). The species is characteristic for grass-heaths on dry, very poor, acidic to weakly acidic soils and for limestone-grasslands on calcareous soils (Boertmann 2010, Krieglsteiner 2001). In Europe these vegetation types are priority plant communities in the Natura2000 network. They are strongly declining all over Europe. H. spadicea has a wide distribution, but it is rare to very rare everywhere (Boertmann 2010) although it may be significantly under-recorded (see Population). The species is assessed as Vulnerable because of an estimated reduction in population size of more than 30% over the last 50 years, a decline caused by habitat loss degradation and suspected to continue in future (Dahlberg and Mueller 2011). This meets the threshold for VU A2c+3c+4c.

---

Taxonomic notes

Hygrocybe spadicea is variable in some characters. In view of research in other species complexes of Hygrocybe it is unlikely that the few records of H. spadicea from North America and New Zealand represent the same biological species as in Eurasia. These records are not considered here.

---

Geographic range

Hygrocybe spadicea has its main distribution in Europe, where it is widespread but rare to very rare. It occurs on very scattered localities from the lowland to the subalpine zone throughout its range (Boertmann 2010). It is also known from a few localities in Asia. For now the records from North America and New Zealand are not considered to be the same species.

---

Population and Trends

Hygrocybe spadicea is widespread in Europe, but rare to very rare on scattered localities throughout its range (Boertmann 2010). Populations are usually very small (1-5 mycelia) and fruiting irregularly. Populations are strongly declining, reflected in its position on many national and regional Red Lists. 

The species is confined to old, semi-natural grasslands in Europe. These habitats are traditionally managed by low intensity grazing and/or hand mowing. Intensification of agricultural practices, grassland conversion and land abandonment are the main threats. Over the last century, more than 90% of semi-natural grasslands have been lost in Europe (EEA Report 3/2016). Available habitats for this species have continuously been lost during that time.

The population size of Hygrocybe spadicea currently exceeds 20,000 mature individuals. The suspected decline of its population across Europe is at least 30% over 30 years (past, ongoing and future). Even higher population decline is possible, up to 50% over three generations (50 years; e.g. 1980-2030). Over the last 50 years, the decline in area of semi-natural grassland habitats in Europe has exceeded 30%. 

The population may be significantly underestimated for this particular waxcap since this species fruits irregularly, shown by recent evidence of increased fruiting after dry summers, probably as a response to draught (Vesterholt 1995, Boertmann 2019).

Population Trend: decreasing

---

Habitat and Ecology

Hygrocybe spadicea is a characteristic species of ancient, unimproved, low productive grass-heaths on very poor, acidic, sandy or loamy soils and on shallow, calcareous soils above limestone. It has a preference for dry, exposed slopes in hilly or mountainous areas (Boertmann 2010). It usually occurs in sites with a rich mycoflora, including many other rare and threatened species. Like other waxcaps, H. spadicea probably lives in biotrophic association with herbaceous plants, but details on its habitat exploitation are unknown. In North-America it also is reported from scrub and frondose forests (Hesler and Smith 1963).

---

Threats

The main threat to Hygrocybe spadicea is loss of habitat by changing land use, including grassland improvement by ferlilizer application and conversion into monocultures for agro-industry; abandoning of seminatural grasslands, followed by natural succession to scrub and forests; forest plantations; inappropriate management, including in protected sites (under- or overgrazing; mowing without removal of the sward, etc). In addition the species is threatened by acidification and nitrogen deposition, also in protected areas. It is included in national Red Lists in at least 16 European countries. It is assessed as Regionally Extinct  (RE) in Poland and Estonia; Critically Endangered (CR) in Czechia and Finland, Baden-Württemberg and Niedersachsen; Endangered (EN) in Croatia, France, Norway, Germany, Austria and Switzerland; Vulnerable (VU) in Sweden; Near Threatened (NT) in Denmark and UK, and Data Deficient in Lithuania and Slovakia.

---

Conservation Actions

A key action for the conservation of this species will be protection of sites where it is known to occur, in particular those with good and regularly fruiting populations, as nature reserves. Continuation of extensive grassland management is essential. The species would benefit from a reduction of air pollution (nitrogen deposition).

More detailed knowledge is needed on the ecological range and characteristics of the habitat, e.g. concerning critical load of nitrogen. Taxonomic research is required, including molecular characters, of populations in Europe, North-America and New-Zealand to find out whether they are conspecific.

---

Source and Citation

Arnolds, E. 2019. Hygrocybe spadicea. The IUCN Red List of Threatened Species 2019: e.T76214469A76214491. https://dx.doi.org/10.2305/IUCN.UK.2019-3.RLTS.T76214469A76214491.en .Accessed on 3 February 2024

---

• Country occurrence