Rising temperatures & ecosystem disturbances are creating a hotbed for fungi that can spark hard-to-treat infections in peoples’ lungs, sinuses & brains.
From lowland tropical rainforests to high-altitude glaciers, southwest China’s Yunnan province boasts a remarkable array of climates, habitats, and ecosystems. With an area larger than Japan, it is a global biodiversity hotspot, renowned particularly for its extensive variety of fungi.
But with temperatures rising due to climate change, and natural habitats in retreat amid rapid urbanization and expanding agriculture, scientists are sounding the alarm over an emerging threat: pathogenic fungi capable of causing life-threatening diseases in humans.
Mycologist Peter Mortimer, a professor at the Kunming Institute of Botany, which is directly affiliated to the Chinese Academy of Sciences (CAS), has a stark warning: “A stressed fungus is a dangerous fungus.”
Increased human activity, he says, is stressing the fungi around the world by “turning natural systems on their heads and disrupting natural processes.” In Yunnan, the fungi have been adapting to such disruptions by developing the ability to feed on unlikely, man-made sources such as plastic and rubber.
Last October, the World Health Organization drew up the first-ever list of fungal pathogens that pose the greatest risk to human health. The list comprises 19 species of fungi that can not only cause potentially lethal infections but are also resistant to currently available drugs.
“The incidence and geographic range of fungal diseases are both expanding worldwide due to global warming and the increase of international travel and trade,” the UN body stated.
Even before the WHO warning, experts in China had emphasized the need for nationwide epidemiological research on fungal infections.
In a 2020 paper titled “Risk-Based Estimate of Human Fungal Disease Burden, China,” researchers from Shanghai’s Huashan Hospital and Fudan University, working with scientists from Beijing and Switzerland, analyzed 70 years of data on fungal diseases in China.
The paper concluded that “high fungal burdens in China, which caused a huge impact on public health, underscore the urgent need for building diagnostic and therapeutic capacity.”
Earlier this year, the dangers fungi pose even made its way even into the realm of pop culture. In the hit TV series “The Last of Us,” a mutated variant of the Cordyceps fungus turns humans into flesh-eating zombies, causing a worldwide pandemic.
Though outlandish, its plot, rooted in science, highlighted the real-world implications of pathogenic fungi. And Yunnan, home to around 100,000 species of fungi, serves as a critical focal point to understand and mitigate the impact of this emerging challenge.
Stress test
On land, fungi are found in virtually every environment, where they play vital ecological roles. Saprophytic fungi break down decaying organic matter, such as dead wood, and return nutrients back into the cycle of life. Mycorrhizal fungi form mutually beneficial relationships with plants, aiding them to better draw nutrients from the soil.
But in some parts of Yunnan, the natural environment of local fungi species is under threat.
To illustrate, Mortimer, who has worked in the region for over 13 years, explains how fungi react when faced with common environmental disruption, like clearing a tropical forest.
“You are a fungus, living a perfectly decent lifestyle — growing on dead wood in a cool, dark forest. Then, suddenly, the soils are exposed to the air, it is also hotter, and it’s drier. And all the substrates on the soils that the fungus eats, like leaf litter or woody debris, are ripped away.”
In such a disturbed ecosystem, animals “either leave or die,” says Mortimer. “But a fungus cannot just get up and walk away.”
Instead, it can adapt. And fungi do so by shape-shifting, becoming completely different organisms.
“There is a total shift in metabolism and physiology, even the appearance and structure change totally, and the fungus looks like a different species,” says Mortimer, adding that this phenomenon is not yet fully understood by scientists.
Once transformed, a harmless wood or leaf-eating fungus “changes its metabolism and produces completely different enzymes,” morphing into a fungus that can digest tissues of living things, including humans.
As part of their reproductive process, fungi release microscopic spores into the air. When spores are inhaled or land on the skin, the fungus can make its way into people’s lungs, blood, sinuses, and even the brain.
“Unlike a virus that hijacks your cellular machinery to replicate, fungi’s mycelium (its root-like structure used for feeding) penetrates your tissues and digests and absorbs nutrients,” explains Mortimer.
Moreover, fungal diseases can be extremely difficult to treat, as highlighted by the World Health Organization’s warning last October.
According to Mortimer, fungal cells, which are similar to animal cells in structure, are very hard to kill with drugs. Consequently, many of the drugs that could potentially be used to combat fungal infections are not suitable for use, he adds, as they would harm human cells as well.
But there is a silver lining. Mortimer explains: “The human body is too hot for fungi. Fungi prefer 25-28 degrees Celsius, whereas our temperatures are more like 36 degrees Celsius. It’s one of the reasons why, historically, fungal diseases have been limited mainly to skin or nail infections.”
But now, as the world gets warmer because of climate change, fungi are adapting to higher temperatures, says Mortimer. This, he explains, “Allows fungal pathogens to get footholds within humans, where they couldn’t before.”
With its vast array of species, Yunnan is a crucial hotspot to study and understand the complexities of fungal adaptations and interactions.
Mortimer says there are probably as many as 100,000 species of fungi in Yunnan, of which just 6,000 are known to science. This biodiversity, he explains, stems from the great variety of habitats, ecosystems, and climates in Yunnan.
According to Mortimer’s research, which is yet to be published, the Shannon index — which measures biodiversity — of the diversity of fungi species in parts of south Yunnan stands at 5.26, which he says is “extremely high.”
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