At least 411 fungi face extinction out of the 1,300 varieties whose conservation status is well understood, according to the latest update of the IUCN's authoritative "Red List of Threatened Species".

"Fungi are the unsung heroes of life on Earth, forming the very foundation of healthy ecosystems -- yet they have long been overlooked," said IUCN director general Grethel Aguilar.

"Now it's time to turn this knowledge into action and safeguard the extraordinary fungal kingdom, whose vast underground networks sustain nature and life as we know it."

This assessment, by the global authority on the status of the natural world, concerns only a fraction of the approximately 150,000 fungal species recorded to date, out of an estimated 2.5 million on Earth.

But it illustrates the strains that human activity places on this distinct individual kingdom, which is neither plant nor animal.

"While fungi mainly live hidden underground and inside wood, their loss impacts the life above ground that depends on them," said Professor Anders Dahlberg, who coordinated this latest assessment.

"It's like the microbiome in our stomachs that are key for our well-being," the Swedish mycologist told AFP, describing a "very, very old symbiosis, more than 400 million years old" which underpin all ecosystems.

"As we lose fungi, we impoverish the ecosystem services and resilience they provide, from drought and pathogen resistance in crops and trees to storing carbon in the soil."

Many fungi "are edible, used in food and drink production including fermentation" and form the basis of medicines, IUCN said.

No porcini mushrooms, chanterelles or other fungi savoured at the dinner table are among the most threatened species.

Dahlberg said most were very specific varieties and not dominant in any one particular fungal community, although some had been fairly common and widespread.

- 'Serious threats' -

Close to 300 of the threatened fungi have been pushed to the limit by the "rapid growth of agricultural and urban areas", said the IUCN, a respected international collective of scientific organisations.

"Nitrogen and ammonia run-off from fertilisers and engine pollution also threaten 91 species," it added.

This in particular poses "serious threats" to popular species in Europe like the fibrous waxcap -- Hygrocybe intermedia -- an uncommon yellow-orange mushroom found in meadows from Scandinavia to southern Italy.

Deforestation, for timber or to make way for crops, is the primary existential threat to at least 198 fungi species.

"Clear-cutting of old-growth forests is especially damaging, destroying fungi that do not have time to re-establish with rotation forestry," said the IUCN.

Iconic species like giant knight -- Tricholoma colossus -- have been classified as vulnerable due to the loss of 30 percent of old-growth pine forests across Finland, Sweden and Russia since the mid 1970s.

Global warming is also a factor, with more than 50 fungi species at risk of extinction due to changes in fire patterns in the United States "which have drastically changed forests", it said.

IUCN said that fir trees had come to dominate the high Sierra Nevada mountain woods, reducing habitat for the endangered Gastroboletus citrinobrunneus.

The latest Red List includes nearly 170,000 threatened species, of which more than 47,000 are threatened with extinction.