After decades in the dark, the fungal kingdom — the second largest after animals — is having a moment in the limelight. Not however, for serving as the backbone of healthy ecosystems, but because it is at risk.  

For the first time in history more than 1,000 species of fungi have been added to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, which is often referred to as the "Barometer of Life."

Like many organisms, these fungi species — which are just a tiny fraction of those believed to exist — are at risk from a combination of factors, including deforestation, urban development and toxins.

"Fungi are especially vulnerable to pollution, particularly from fertilizers and fossil fuel emissions," said Lynne Boddy, an expert in fungal ecology at Cardiff University. 

She said protecting fungi requires target action, because they have "specific needs and must be considered on their own merits in conservation efforts, and not just lumped in with other organisms."

Not the cutest species in the forest?

But raising awareness around fungi — which are often seen as a pizza topping or an unwanted addition to a damp wall — is not always easy.

"Lots of people care about animals, particularly if they're cuddly, friendly organisms that people sort of have an affinity to, like pandas," said Boddy, adding that most fungi don't have that emotive effect.

"Maybe humans can't get their hearts around those."

Fungi may not win cuteness contests, but they play an important role in holding the entire web of life together. Depending on their type, fungi are found in diverse environments: from soil and forests to freshwater lakes, marine ecosystems and even human skin.

Mycorrhizal fungi support forest ecosystems by helping plants to exchange nutrients, water and even information, form symbiotic relationships with the roots of most flora and are essential for growth in as many as 90% of plant species.

In other words: "Life on Earth depends on fungi," said Gregory M. Mueller, chief scientist at Chicago Botanic Garden.

They are also key to death on Earth. Known as nature's recyclers, they break down dead or decaying wood, leaves and other plant matter. "Without them, we'd be buried under mounds of organic waste," said Mueller, who leads the IUCN fungal programs and contributed to the recent Red List.

Fungi has key role in carbon capture, food security 

While forests and grasslands are generally held up as carbon stores, it is fungi that helps capture carbon in the soil. Mueller said fungi are "essential for long-term carbon sequestration," the process of locking carbon away so it doesn't contribute to global warming.

"Without them, climate change would be much worse," he said.

Mycorrhizal fungi are responsible for storing up to a third of annual global fossil fuel emissions in the soil. That makes it the most efficient carbon storage facility in the world.

At the same time, fungi are affected by climate change, largely through changes in hydration levels. Mueller cites the example of Brazil, where cloud forests in the mountains depend on certain moisture levels, which have been decreasing in tandem with changing rainfall patterns. 

He said this not only changes the habitat but "affects the plants on which the fungi depend; they dry out and prevent the fungi from completing their life cycle."

A world without fungi would not only be made less hospitable to human life by rising global temperatures and connected extreme weather events, but trees and crops would grow weaker, slower and become more vulnerable to disease and drought. 

And that would impact the availability of food and drugs. Around 40% of modern drugs in the Western world are derived from plants. These include, for example, galantamine, which is derived from Galanthus nivalis to treat Alzheimer's disease, or apomorphine, a semi-synthetic compound extracted from morphine, Papaver somniferum, that is used to treat Parkinson's disease.

Fungi are such an integral part of the web of life that if they disappeared, most life forms, including humans, would not survive.

"If there were no fungi in the soil, I don't think there would be life on Earth. Plants likely colonized land alongside fungi and without them, the world as we know it might never have existed," said Aishwarya Veerabahu, a scientist with the Department of Botany at the University of Wisconsin-Madison.

How can we protect endangered fungi?

Only in 2021 did the IUCN start treating fungi as equal to flora and fauna in terms of conservation.

"That change was a major step," said Boddy, adding that it was now important to identify which fungi are at risk and find ways to reduce the threats against them. 

Scientists have so far formally identified about 155,000 fungal species, but it's estimated there are at least 2 million and maybe upwards of 3 million that have yet to be discovered.

That means we "know almost nothing about most of them and some may go extinct even before we discover them," Veerabahu told DW. 

Forest and grassland management, which means planned interventions in these ecosystems, should be done with fungi in mind, so they don't harm them.

This may include, for example, "maintaining enough trees and woody debris" during deforestation to provide a breeding ground for fungi and limiting "fertilization in agricultural systems and natural grasslands, as fertilization reduces the number and types of beneficial fungi in soils," said Mueller.

"We can't afford not to include fungi. Conservation without fungi is incomplete."

Edited by: Tamsin Walker, Sarah Steffen