The Tyler Prize for Environmental Achievement, sometimes described as the “green Nobel Prize”, was awarded last month to Toby Kiers, an evolutionary biologist at Vrije University Amsterdam in the Netherlands.
Last year, Kiers won a MacArthur “genius” award and the Climate Breakthrough Award, sharing it with Giuliana Furci, a fungi conservationist, and Merlin Sheldrake, a mycologist at the University of Oxford, UK.
The fungal kingdom, which stands apart from plants and animals, contains anywhere from 2 million to 5 million species, including yeasts, mildew, lichens and mushrooms. Kiers studies mycorrhizal fungi, microbes that form vast, underground networks with carbon drawn from the roots of plants and trees, providing vital nutrients in exchange.
Kiers and her colleagues have calculated that these microbial filaments, laid end to end, would span half the galaxy and that they sequester 13 billion tons of atmospheric carbon dioxide — one-third of the world’s fossil-fuel emissions — in the soil each year.
These brainless, distributed organisms are also astonishingly strategic in their business dealings, her team has shown, imposing tariffs and inflating prices. In 2021, Kiers founded the Society for the Protection of Underground Networks or SPUN, a global network of researchers and “underground explorers” that works to identify and protect hot spots of fungal diversity. Last year they unveiled the first global underground atlas. And a new initiative called Underground Advocates, developed with the More-Than-Human Life programme at the New York University School of Law, US, helps train scientists in legal and policy skills.
The conversation was edited for clarity and brevity.
Q Why fungi?
These underground ecosystems play a crucial role in regulating the climate. Soils store about 75 per cent of Earth’s terrestrial carbon and contain close to 60 per cent of Earth’s biodiversity. Mycorrhizal fungi form the basis of food chains for those aboveground organisms, which together generate more soil and nutrients. People think they know what soil and dirt is. With high-resolution imaging, we’re starting to make it visible and show that it’s alive. These are ecosystems, with as much complexity as what’s happening aboveground. I think 2026 is really going to be the year where people start talking about fungal restoration. It’s not enough to just add native plants to restore ecosystems; it has to be native plants together with native fungi.
Q How did you and fungi meet?
When I was 19, I became so enchanted by the idea of being a field biologist that I left college, not knowing if I’d come back, and spent a year at the Smithsonian Tropical Research Institute, a research station on an island in the middle of the Panama Canal. I needed a niche. At the time, mycorrhizal fungi were pretty unknown there. The older scientists were studying everything above ground — trees, bats, primates. I started wondering what generated all that diversity. So I did an experiment with researchers where we took soil from underneath the trees of one species and used it to inoculate other tree seedlings to see if it would affect their growth. We stained the roots with a dye, and you could see this intricate weave of fungi inside the cells — they penetrate it — called an arbuscule; it looks like a mini tree. That’s where nutrient exchange happens. And I could see that happening in the roots with my own eyes.
Q For a long time, mycorrhizal fungi were viewed as pathogens, right?
I was there as the perception was starting to change. Studies were starting to show that plants actually get huge benefits from fungi. Later, I realised that they’re powerful actors in their own right. My PhD thesis explored whether non-cognitive organisms can discriminate between good and bad partners. For instance, from experiments, we know that plants will digest one of those arbuscules if they’re not getting enough phosphorus from the fungus; they can abort the interaction. But the fungi make choices as well. We found that a fungus can avoid trading with plants in the shade, which have less carbon to trade. They trade differently depending on how many other fungal competitors are present. They can hoard resources in their network and artificially inflate the price.
Q Trade wars! So a fungus is a bit like a stockbroker or merchant.
Exactly. Are fungi capitalists? No. They’ve developed a system that is much more sophisticated than the economic system humans use. But it has allowed us to use economics as a mathematical framework to analyse these trade strategies, to make predictions and to see if the fungi follow them. The frontier is linking what we’re seeing on the micron scale to the global data to understand the role of fungi in the carbon cycle.
Q Meanwhile, in SPUN, you’ve built a network of investigators to map the global distribution of networked microorganisms.
We wanted to turn the traditional approach on its head. SPUN has become a rambunctious, decentralised community of people working together to study and protect underground fungi. We’re slightly outside academia while still adhering to rigorous science and publishing in top journals. That helps us. In an academic setting, you almost have to know what you’re going to find before you’re funded to find it. I use the term “punk science”. We’re trying to cross boundaries and disciplines and not accept the state of the world as a given, while celebrating science that is rooted in creativity.
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