Only 0.6% of known fungi have an IUCN assessment

The figure of 0.6 per cent comes from the report State of the World's Plants and Fungi 2026 by the Royal Botanic Gardens, Kew. The authors set the number of fungal species holding a formal IUCN Red List assessment against the number of species known to science. It is a share of assessments, not the proportion of all fungi threatened with extinction. The two figures must not be equated.

A formal IUCN assessment requires data on range, the number of sites or individuals, trend, habitat and pressures. Gathering these is particularly difficult for fungi. Most often we record short-lived fruiting bodies, while the mycelium remains invisible. The boundaries of an individual are often unclear, and years without fruiting bodies need not mean it has gone. An assessment therefore requires a series of observations, knowledge of the habitat and a documented method of inference.

The indicator describes the state of knowledge in 2026. It will change both when the IUCN publishes new assessments and when taxonomists describe further species. It is not a live counter. Nor can 0.6 per cent be multiplied by the estimated number of undescribed species, because the assessed group is not a random sample of the whole kingdom.

The most important conclusion is organisational: the conservation of fungi needs taxonomy, continuous monitoring and habitat data in parallel. A list of names alone will not show a trend, and a record of observations without controlled identification may confuse species. The figure of 0.6 per cent therefore says more about the information gap than about the degree of safety. An absence of assessment means, above all, an absence of adequate knowledge.

Six assessments per thousand known species

Kew’s 2026 report states that 0.6% of fungal species known to science have a formal IUCN Red List assessment. In practical terms, that is about six assessments for every thousand named species. The remaining 99.4% cannot automatically be treated as secure: not assessed is a data gap, not a least-concern category.

The denominator is known species rather than the estimated 2–3 million total diversity. This is why the card does not duplicate the count of 1,300 assessments. One statistic measures coverage of the catalogue; the other reports completed assessments and their threatened subset.