A rainforest growing in sand benefits from the mycorrhizal fungi in...

A rainforest growing in sand benefits from the mycorrhizal fungi in the sand that release nutrients to be absorbed by plants, in Orchid Beach, Great Sandy National Park, Fraser Island, Queensland, Australia. Credit: Universal Images Group via Getty/Auscape

Toby Kiers is a professor of evolutionary biology at Amsterdam's Vrije Universiteit whose research on fungi has led her to revelations about how nature itself can solve the climate crisis. Kiers is looking beyond the astonishing diversity of mushrooms we see growing above ground to the hidden systems we overlook: fungal webs that spread throughout the soil and nourish the roots of trees and plants.

In her laboratory, streams of carbon molecules flow across Kiers' computer screen like the oily bubbles in a lava lamp. Lit up and magnified, the carbon is moving through an infrastructure of gossamer tubes that make up vast underground networks of fungi. These systems comprise a third of the living biomass of soil, binding it together and sustaining much of life on Earth. Soils contain about 75% of the planet's terrestrial carbon, and fungi play a critical role. They are "powerful and underappreciated allies" in the quest to solve climate change, said Kiers.

Monday, the scientific journal Cell Press is publishing a groundbreaking study co-authored by Kiers, to which Bloomberg Opinion was given early access, revealing that a group of fungi known as mycorrhizae draw down and store more than 13 million tons of carbon dioxide annually. That's nearly the annual greenhouse gas output of China and the U.S. combined.

The study is the first to calculate how much carbon moves through these subterranean networks. The implications are critical not just for climate scientists, but also for policymakers, investors and innovators — all of whom must come to understand and support the role fungi will play in the global effort to remove excess carbon from our atmosphere.

Support is critically needed: The planet's mycorrhizal networks are under siege from deforestation and industrial agriculture, which depletes these systems through tilling and the over-application of chemical fertilizers and pesticides. Heat, drought and other climate pressures are also taking a toll. Given current trends, more than 90% of the Earth's soil will be degraded by midcentury — and so will the networks of fungi within them.

By quantifying the significance of fungi, Kiers's study suggests a road map for action. The U.S. Agriculture Department must not only expand research efforts into this area, it should incentivize the shift toward regenerative agriculture. There should be rewards — if not requirements — for no-till farming, which leaves the soil and its living biomass undisturbed while improving crop yields and saving money. This method is used on only about a third of U.S. farmland and deserves mass adoption.

Investors can do their part by funding the development of precision agriculture tools, including emerging AI agricultural robots and drone technologies that can cut chemical use by up to 90%. Innovators working on carbon capture and storage technologies, which are drawing huge flows of capital, should borrow models from the research on mycorrhizal networks: This vast living machine offers ingenious insights into the sequestration of carbon.

Kiers described mycorrhizae as "tiny capitalists" that provide nitrogen, phosphorous and other nutrients to the roots of trees and crops in exchange for the carbon those plants draw in through photosynthesis. The fungus then uses that carbon to grow, creating a virtuous cycle of nourishment between above- and below-ground systems.

These fungi can naturally provide more than 80% of a plant's nutrients. But crops laden with chemical fertilizers often fail to transfer their carbon to the fungi, harming the underground networks.

Even in its current beleaguered state, the intricacy of the underground system is extraordinary: If stretched into one long filament, the total length of fungal networks in soil worldwide is about half the width of our galaxy. "This is a 400 million-year-old life-support system that easily qualifies as one of the wonders of the living world," Kiers told me.

Perhaps even more staggering is how little we understand: Which species of underground fungi are best not only at pulling carbon from plant roots, but also conducting and holding onto it? We don't yet know. Kiers is exploring the role of "exudate," a fungal compound that helps makes soil "sticky," binding it together while fending off bacteria that continually eat away at the networks, releasing stored carbon. How can exudate and other compounds be increased so that more carbon stays locked underground?

There are likely tens of thousands of species of underground fungi that have yet to be discovered and researched. Once scientists understand and map this realm, they could "nudge" the system to increase its carbon-carrying capacity.

Kiers travels across the world to collect soil samples packed with fungi, working with a global collective of local scientists through her newly founded Society for the Protection of Underground Networks, or SPUN. They use AI models to predict hot spots of mycorrhizal biodiversity. On location, they scan the landscape for mushrooms known as "fruiting bodies" that you see above ground — slimy, purply, hairy, waxy, diaphanous — which can function as periscopes for the networks beneath the surface. They extract fungal DNA and send it out for sequencing.

This sampling project, a collaboration with GlobalFungi and the Crowther Lab, aims to span 10,000 locations and assemble an open-source map of the planet's fungal networks. The maps will help chart carbon sequestration hot spots and identify the fungal species that can best tolerate drought and heat — and could be useful to introduce into the soils of vulnerable croplands.

Kiers's research provides a promising new arena for fighting climate change — but only if climate scientists, policymakers and investors use this new knowledge to design conservation strategies and food systems that increase yields while protecting, not degrading, the underlying web of life.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners. Amanda Little is a Bloomberg Opinion columnist covering agriculture and climate. She is a professor of journalism and science writing at Vanderbilt University and author of "The Fate of Food: What We'll Eat in a Bigger, Hotter, Smarter World."

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