Cuphophyllus radiatus belongs to the European waxcap assemblage whose members are globally red-listed based on the declining area/quality of their grassland habitat. This assemblage is declining across Europe due to changes in land use (agricultural intensification and decline of traditional farming practices) and increasing use of fertilizers and pesticides.
Decline in area and quality of available habitat has approached (or possibly exceeded) 30% over the last 50 years; the decline in population size over this time could be higher. This decline in habitat is expected to continue even more rapidly over the next 50 years (approximately three generations: one generation for species of Hygrocybe s.l. is around 17 years). This species meets the threshold for VU A2c+3c+4c. However, further data regarding the full distribution of the species is required, to help to produce an accurate population size estimate; as it is suspected to be a very rare species and could warrant uplisting in the future.

Cuphophyllus radiatus (as Hygrocybe radiata Arnolds 1989) was accepted as a distinct species in Boertmann edn1 (1995), but not in Boertmann edn2 (2010). However DNA analysis (Dentinger et al. unpubl.) supports its recognition as a distinct species.

This taxon has been poorly understood in the past and so has only been recorded as Hygrocybe radiata or Cuphophyllus radiatus by a few recorders. Hence the true distribution is unknown. The distribution map is therefore restricted to the origins of the holotype collection (the Netherlands), those countries reported in Boertmann edn 1 (1995) and the source country (UK) of those DNA barcode sequences (Dentinger et al., unpubl.) derived from specimens morphologically matching the original description and/or identified by the author of the species’ name. No matches have been found with sequenced material from N. America and this species is therefore regarded as having a European distribution. It is expected that this species will be shown to have a much wider European distribution when the results of further DNA barcoding studies become available, but it is suspected on the basis of current data that C. radiatus will remain one of the relatively rarer members of the waxcap grassland community.

The population size is unknown, and is very difficult to quantify at the current time.  The population is decreasing in all known occupied European countries, caused by a cessation of small scale farming and traditional methods of grassland management. The eastern boundary of the range is, as is the case for all members of this assemblage, unclear because of lack of data.
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 y (1990-2003); only a few Member States managed to avoid this trend (Food and Agricultural Organisation of the United Nations 2006: FAO Statistical Yearbook – FAOSTAT). Based on this, the decline is inferred to be 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.

Cuphophyllus radiatus is an indicator of mycologically rich but nutrient-poor, semi-natural grassland (a member of the waxcap grassland assemblage). This habitat, which may be of low conservation concern for its plant and animal diversity, is rapidly disappearing worldwide due to changes in land use (intensification of farming practice, eutrophication and increased use of fertilizers and pesticides). Waxcaps are currently regarded as forming a biotrophic relationship with plants but the details remain unclear. Fruiting populations of waxcaps are nitrogen sensitive and dependent on a regime of grazing or mowing without applications of fertilizer or pesticide. The waxcap grassland assemblage is characterised by a large diversity of other fungal genera (including Entoloma, clavarioid taxa and geoglossoid taxa) that have similar nutrient and management requirements. Addition of fertilizers or cessation of grazing/mowing management is rapidly detrimental to fruiting community diversity.

As a species dependent on semi-natural grasslands, Cuphophyllus radiatus is threatened by habitat loss and degradation due to a decrease in small scale, low intensity farming. The main reasons for decline involve land that is no longer farmed or, if still in the farming system, is subjected to ploughing, reseeding, fertiliser application (mainly of phosphorus and nitrogen), reduced grazing intensity and eutrophication.
According to NATURA 2000 reports (Calaciura and Spinelli 2008), grassland habitats are steadily decreasing, mainly due to abandonment or change in land use. 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 (Food and Agricultural Organisation of the United Nations 2006: FAO Statistical Yearbook – FAOSTAT). Pressure caused by land use changes on grassland habitats is steadily increasing. Some 60% of newly afforested areas in the EU formerly was used as permanent/seasonal grazing land or hay-production in natural meadows.
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. Over the past decade, grassland butterflies have suffered large declines in Europe, with a reduction of abundance by almost 50%, with little sign of improvement (SEBI 2010 Biodiversity Indicators).
According to the European Environment Agency (2015), natural and semi-natural grasslands have undergone a major decline in recent decades. Grasslands have one of the lowest proportions (11%) of favourable condition assessments and one of the highest proportions of decreasing as-sessments of all the terrestrial ecosystems considered. About 49 % of EU assessments for the 45 grassland habitat types of Community interest are “unfavourable-bad”. Moreover, almost 50% of grassland-associated birds are declining and the conservation status of other species is mostly “unfavourable”. Grassland butterflies, for example, are declining severely and there is no sign of level-ling off. Accordingly, Janssen et al. (2016) (European Red List of Habitats) reported that 53 % of the grassland habitats in Europe are threatened to some degree (the second most threatened habitat type after “mires and bogs”).

Site protection and management of habitats are both very important conservation actions for this species.
Grazing, at least before the onset of the fruiting season, is of fundamental importance. On sites (e.g. sloping ground, thin soils) where cattle would cause soil erosion, sheep are the preferred grazing animal. Mowing, with collection of ‘arisings’, can substitute for grazing.

Further ecological research needed to clarify resource relations of waxcaps and further DNA-supported work required to fully understand the distribution of this species.

Boertmann D (1995) The genus Hygrocybe. Fungi of Northern Europe 1. Danish Mycological Society, 1–184.

Boertmann, D. (2010). The genus Hygrocybe. Fungi of Northern Europe 1. 2nd revised edition. Danish Mycological Society, Copenhagen.

European Environment Agency (2015). State of nature in the EU. Technical report No 2/2015. European Environment Agency, Copenhagen.

J.A.M. Janssen, J.S. Rodwell, M. García Criado, S. Gubbay, T. Haynes, A. Nieto, N. Sanders, F. Lan-ducci, J. Loidi, A. Ssymank, T. Tahvanainen, M. Valderrabano, A. Acosta, M. Aronsson, G. Arts, F. Attorre, E. Bergmeier, R.-J. Bijlsma, F. Bioret, C. Biţă-Nicolae, I. Biurrun, M. Calix, J. Capelo, A. Čar-ni, M. Chytrý, J. Dengler, P. Dimopoulos, F. Essl, H. Gardfjell, D. Gigante, G. Giusso del Galdo, M. Hájek, F. Jansen, J. Jansen, J. Kapfer, A. Mickolajczak, J.A. Molina, Z. Molnár, D. Paternoster, A. Piernik, B. Poulin, B. Renaux, J.H.J. Schaminée, K. Šumberová, H. Toivonen, T. Tonteri, I. Tsiripidis, R. Tzonev and M. Valachovič, (2016). European Red List of habitats. Part 2, terrestrial and freshwater habitats. European Union, Luxembourg.

Kautmanova, I., Knutsson, T., Krikorev, M., Læssøe, T. & Senn-Irlet, B. 2015. Hygrocybe ingrata. The IUCN Red List of Threatened Species 2015: e.T71595761A71595999. http://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T71595761A71595999.en. Downloaded on 21 February 2018.

Kautmanova, I., Knutsson, T., Krikorev, M., Læssøe, T. & von Bonsdorff, T. 2015. Hygrocybe citrinovirens. The IUCN Red List of Threatened Species 2015: e.T70406652A70406717. http://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T70406652A70406717.en. Downloaded on 21 February 2018.

Lodge D.J., Padamsee M., Matheny P.B., Aime M.C., Cantrell S.A., Boertmann D., Kovalenko A., Vizzini A., Dentinger B.T.M., Kirk P.M., Ainsworth A.M., Moncalvo J.-M., Vilgalys R., Larsson E., Lücking R., Griffith G.W., Smith M.E., Norvell L.L., Desjardin D.E., Redhead S.A., Ovrebo C.L., Lickey E.B., Ercole E., Hughes K.W., Courtecuisse R., Young, A., Binder M., Minnis A.M., Lindner D.L., Ortiz-Santana B., Haight J., Læssøe T., Baroni T.J., Geml J., Hattori T. (2014). Molecular phylogeny, morphology, pigment chemistry and ecology in Hygrophoraceae (Agaricales). Fungal Diversity 64:1-99.