The Red List still sees only a sliver of fungi

In March 2025 the IUCN reported more than 1,300 assessed fungal species, of which at least 411 were considered threatened with extinction. Reaching the first thousand was an important organisational threshold, but it does not mean we know the proportion of threatened species across the whole kingdom. Even among fungi already described, formal assessments cover only a small fraction. The 2026 Kew report estimates that share at about 0.6 per cent.

An IUCN assessment is not an intuitive opinion about rarity. It requires data on range, number of locations, population trend, habitat and threats, and then the application of published criteria. With fungi a particular problem arises: we mostly observe short-lived fruiting bodies, while the individual and its boundaries may be hidden in soil, wood or a living host. Years without fruiting bodies do not always mean the organism is absent.

Nor can we conclude that 411 threatened species is the complete figure, or that the proportion in the assessed sample can simply be multiplied across all species. Taxa for which data or a suspicion of threat exists are assessed more often, so the sample is not random. On the other hand, tropical, subterranean and microscopic species are more poorly documented. The honest message is this: we know specific threats within the assessed group, and at the same time the scale of our ignorance is large.

The priority becomes combining herbaria, sequences, repeated observations and habitat information. The Red List can then direct conservation towards particular places and processes, rather than serving as a catalogue of remarkable names. For a field observer, documentation of the host, the substrate, the number of fruiting bodies and changes to the habitat is valuable; the precise location of a rare species should be shared with care.

The counter needs a release number

IUCN Red List 2025-2 assessed 1,302 fungal species in “Mushrooms, etc.”; 411 were classified as threatened—CR, EN or VU. That is only 0.8% of the 157,648 described species used in IUCN's table. Dividing 411 by 1,302 does not show that 31.6% of all fungi are threatened: IUCN explicitly labels coverage insufficient, while assessed taxa are biased toward well-known or already suspected species. Version 2026-1 still describes the total as “over 1,300.” Counts rise through first assessments, reassessments and taxonomic revision, not only because nature is deteriorating. A real trend requires documented genuine category changes and the Red List Index, not the raw number of listed species.