Assessment Notes

Justification

Craterellus atrocinereus is a rare Craterellus from California and Oregon, USA. It is currently known from approximately 30-50 locations, from a habitat that is in decline. The extent of occurrence is large (133,181 km²), but being restricted to only a limited number of sites the area of occupancy is small (minimum 120-200 km², and while this may be an underestimate it is unlikely to exceed 2,500 km²). Therefore, it nearly meets the requirements for listing as threatened under criterion B2, and is assessed as Near Threatened.

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Taxonomic notes

Craterellus atrocinereus was historically referred to by the name of a European species, C. cinereus (Thiers 1985, Arora 1986). The distinct western North American species was described from a type collection made in Santa Cruz County, California, USA (Frank 2015).

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Geographic range

Craterellus atrocinereus is known from Santa Cruz County, California, USA, north into Oregon; but reports are highly disjunct across this range, with reports from approximately 30-50 sites. The extent of occurrence is large, at 133,181 km², but being restricted to only a limited number of sites the area of occupancy (AOO) is small with a minimum AOO of 120-200 km². While this is likely an underestimate it is unlikely to exceed 2,500 km².

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Population and Trends

The distribution of this species is wide, but it is rarely reported, and subpopulations are highly disjunct. Currently it is known from c.75 observations (exact localities are hidden on a few records, and this number could represent anywhere from 30-50 distinct sites) (iNaturalist 2021, Mushroom Observer 2021, and MyCoPortal 2021, where many are listed as Craterellus cinereus).

Data to fully assess the population trend are lacking, but it is likely declining. Stand replacing fires, especially in the southern portion of the range have drastically altered habitat, likely making it ill-suited for Craterellus atrocinereus, as has the decline of Tanoak Notholithocarpus densiflorus, and to a lesser extent, live oak Quercus spp., due to the introduced pathogen, Sudden Oak Death (Phytophthora ramorum).

Population Trend: Decreasing

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Habitat and Ecology

Craterellus atrocinereus is ectomycorrhizal with hardwoods; especially Tanoak (Notholithocarpus densiflorus), Coast Live Oak (Quercus agrifolia) and Oregon White Oak (Q. garryana). Often it is scattered in small clusters or groups, with fruiting in late winter and spring.

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Threats

Local subpopulations in the San Francisco Bay area are under threat due to the introduced pathogen Sudden Oak Death (Phytophthora ramorum), which is killing large swaths of Tanoak, and to a lesser extent live oak. Stand replacing fires, especially in the southern portion of the range have drastically alter habitat, likely making it ill-suited for Craterellus atrocinereus in the near term, and is likely detrimental to this species, due to the limited subpopulations and spore production for reintroduction. Habitat declines due to urban development are an additional threat.

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Conservation Actions

It is necessary to limit the spread of Sudden Oak Death in northern California forests. Research is needed to investigate the total extent of range, and the population size of this species, as well as collating data to assess trends and threats.

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Use and Trade

Craterellus atrocinereus is a highly desired edible species, and is collected by hobbyist foragers, although not specifically targeted like the common relative, C. calicornucopioides.

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Source and Citation

Siegel, N. 2025. Craterellus atrocinereus. The IUCN Red List of Threatened Species 2025: e.T189958384A198624536. Accessed on 22 November 2025.

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• Country occurrence