New IUCN Red List: Over 400 fungi threatened—a warning signal for biodiversity

Fungi are masters of the hidden. They live mostly out of sight—in the soil, in dead wood, as tiny spores in the air, or in close partnership with plants. Precisely because they are so inconspicuous, they are often overlooked in conservation. Yet they are indispensable for the functioning of our ecosystems. The International Union for Conservation of Nature (IUCN) now warns: more and more fungal species are at acute risk of extinction—with far-reaching consequences for life above ground.

1,300 fungal species on the Red List—over 400 threatened

With the latest update of its Red List, the IUCN has for the first time crossed the threshold of 1,000 assessed fungal species. A total of 1,300 species are now listed—including 129 as Vulnerable, 234 as Endangered, and 48 as Critically Endangered. And this is only a small excerpt: worldwide, only around 155,000 fungal species have been scientifically described so far, but estimates suggest there may be up to 2.5 million species. The true number of threatened fungi is therefore likely many times higher.

The causes of the decline are diverse—and human-made: the destruction of forests for agriculture, settlement expansion, and logging destroys valuable habitats. Added to this are air pollution from nitrogen and ammonia from fertilizers and exhaust fumes, intensive agriculture, climate change, and altered fire regimes. All these factors strain fungi’s delicate, often invisible networks—and tip the ecological balance.

Threatened species: from the colossal knight to the waxcap

The decline affects far more than unknown microfungi—species that once belonged to Europe’s typical cultural landscapes are disappearing too. One of them is the fibrous waxcap (Hygrocybe intermedia), now classified as Vulnerable—and trending downward. Its habitat: nutrient-poor, semi-natural meadows. But those meadows are becoming increasingly rare. Intensive agriculture, fertilization, and pesticide use are steadily wiping them out. The waxcap is sensitive to nitrogen and depends on extensively managed land—meadows that are regularly mown or grazed but not fertilized. If this traditional management stops, the characteristic diversity of grassland fungi disappears—the Intermediate waxcap is just one of many species that suffer.

The impressive giant knight (Tricholoma colossus) is also under pressure. In the Netherlands, it is already considered extinct. The reason: widespread logging of old pine forests, especially in Finland, Sweden, and Russia. Since 1975, around 30 percent of old-growth stands there have disappeared. The colossal knight is closely tied to these near-natural forests and hardly returns after clear-cutting—replanted production forests do not provide suitable habitat. In addition, its occurrence is further restricted by the expansion of cities, roads, and military areas. According to the IUCN, about a third of its potential habitat could be lost over the next 50 years.

Climate change is also taking its toll: in the U.S., more than 50 fungal species are threatened by altered fire regimes. One example is Gastroboletus citrinobrunneus, a rare species that occurs only in certain forest areas of the Sierra Nevada. These forests have changed drastically in recent decades. Prolonged droughts, insect outbreaks, and decades of fire suppression have turned once open conifer forests into dense fir stands. The result: large-scale, intense fires that destroy the habitat of this specialized fungus. The open forests that Gastroboletus citrinobrunneus needs are becoming ever rarer—and with them, the species disappears.

​The rediscovery of the big puma fungus (Austroomphaliaster nahuelbutensis) in 2023 in Chile, a species that had been considered missing since the 1980s, shows that despite worrying trends there are also positive developments.

Why fungi are irreplaceable

Fungi are neither plants nor animals—they form their own biological kingdom. With an estimated 2.5 million species, they are the second-largest kingdom on Earth after animals. And they are far more than just a “by-catch” of biodiversity: without fungi, life as we know it would not be possible.

Almost all plants form symbioses with mycorrhizal fungi, which enter into a partnership with plant roots. They help plants absorb water and nutrients from the soil. Fungi decompose dead material, store carbon, strengthen plants against disease and drought stress, and stabilize entire communities. They are indispensable for healthy soils—and thus also for our food, our climate, and our future. In addition, fungi are used in food production, in medicine, and in the remediation of contaminated soils.

Swedish mycologist Anders Dahlberg, who coordinates the fungal assessments for the IUCN, draws a striking comparison: fungi are like the human body’s microbiome—invisible, yet vital. Their loss weakens not only biodiversity but also the resilience of entire ecosystems.

Protecting fungi means securing the future

The IUCN calls for the often overlooked “kingdom of fungi” to finally be given the attention it deserves. Protecting fungi is crucial for stable ecosystems and a healthy environment. The most important measures include:

• preserving old forests with abundant dead wood,
• fungi-friendly forestry that leaves dead wood in place and preserves habitats,
• reducing pollutant inputs from agriculture and traffic,
• and expanding research to identify fungal species that are still unknown or unrecognized as threatened.

Many of these measures can be implemented locally—for example through adapted land management or protected areas. But they need support from politics, society, and science. Protecting fungi is not a side note; it is part of the answer to bigger challenges: biodiversity loss, the climate crisis, and soil degradation. Fungi are (silent) co-creators of our natural world—if they disappear, many species lose the basis of their existence.

When foraging: respect the mycelium

Another often underestimated aspect is responsible foraging for wild mushrooms. Anyone who tears the entire fruiting body out of the ground along with the mycelium damages the fungus permanently—because without mycelium it cannot survive or regenerate. Sustainable harvesting means carefully cutting the fruiting bodies with a knife and leaving the fine fungal network in the soil untouched. Only then will the fungi’s invisible lifeline be preserved.

Frankincense trees and lions are also under pressure

The Red List update not only highlights the global decline of fungal species—it also draws attention to two very different, yet equally threatened, species: the frankincense tree and the lion.

On the Yemeni island of Socotra, several species of the legendary frankincense tree (Boswellia) are now endangered or even threatened with extinction. The main causes are overgrazing by goats, prolonged droughts, and increasingly extreme weather events such as cyclones and flash floods. Goats have been part of local culture for centuries, but without controlled grazing, young trees are coming under increasing pressure. Local conservation measures such as fencing off young trees or sustainably using the resin—for example to produce frankincense honey—offer hope. They show that early, community-supported action can work.

For the lion, the Green Status assessment—which indicates how well a species has recovered—provides important insights. While the species is still listed as threatened, its ecological condition is now considered “largely depleted”. In North Africa and Southwest Asia, the lion is already extinct. At the same time, the assessment also shows that targeted conservation measures in parts of Africa and in India have prevented local extinctions. That offers hope—but also underscores how urgently stronger action is needed to stop the species from disappearing in more regions.

Both cases show that the Red List is more than a list of threatened species—it provides concrete indications of what works, where progress is being made, and where urgent action is needed to preserve the world’s biodiversity.