The Climate Solution Under Your Feet: Mapping Earth's Hidden Fungal Networks Beneath every forest, grassland and farm is a living network most of us have never seen. Mycorrhizal fungi partner with about 90% of land plants. They trade nutrients for carbon in a relationship that is 450 million years old, and they pull a staggering amount of CO₂ into the soil every year. Matt sits down with Jason Cremerius, Managing Director and Chief Strategy Officer of SPUN (the Society for the Protection of Underground Networks). SPUN was co-founded by evolutionary biologist Toby Kiers, who recently won both a MacArthur "genius" award and the Tyler Prize, often called the Nobel Prize for the environment. SPUN's mission is to map the world's underground fungal networks so that we stop making decisions based only on what we can see. The conversation covers: How fungi bury carbon in the soil, mostly through their own dead bodies ("necromass")Why grasslands turned out to hold some of the densest fungal networks on EarthHow SPUN built a global map at 1 km² resolution using machine learningThe goal of eventually detecting fungal communities from spaceWhy 80–90% of commercial fungal inoculants arrive deadWhy monoculture tree planting so often failsJason also brings a venture lens. He started in venture studios and corporate VC, so he makes the investment case for: Microbial-scale biological sensingNature credits that measure what actually mattersFungal startups like FungaSupply-chain biodiversity intelligenceA hybrid philanthropic-venture model he calls "DARPA for the environment"He closes on what gives him hope: standing in the rain in western Britain, watching researchers study the soil to bring back a lost temperate rainforest. Episode description (short, for the feed / social)Fungi under our feet pull roughly 13 billion tons of CO₂ into the soil every year, and we've barely mapped them. Jason Cremerius of SPUN explains how fungal networks hold up the living world, why grasslands are a hidden carbon story, and where the investable opportunities are in "nature data." He also explains why the next frontier is down, not up. Chapters / timestamps00:00 — Welcome: Williamsburg vs. Greenpoint, and the dreaded G train01:25 — Is there a mycelial network under Brooklyn? Sampling under-sampled cities02:30 — What is SPUN? Founding story and Toby Kiers03:09 — Mycorrhizal fungi 101: 90% of plants and a 450-million-year partnership04:16 — Beyond the "wood wide web": the carbon story05:48 — Carbon for nitrogen and phosphorus, and how trees learned roots from fungi07:29 — Necromass: how fungi bury carbon as they live and die08:25 — 13 billion tons a year, about a third of fossil emissions09:37 — Do fungi help trees pull down more carbon? Biodiversity, turnover and a 64% productivity boost11:37 — The grassland surprise12:26 — California's grassland fires and how quickly grasslands can recover13:51 — New species, globally rare fungi, and why so few fungi are on protected-species lists15:38 — From data to products? Long-read DNA sequencing16:50 — How the map is built: 25,000 samples, GlobalFungi, and machine learning at 1 km²18:28 — Getting to 10–30 meters: seeing fungi from space with satellite data20:36 — Mapping the underground like the deep ocean, including SPUN's deep-soil work22:28 — Toby's lab: robotics and machine learning that track carbon inside individual fungal threads23:20 — The investor lens: Jason's venture studio background24:48 — Opportunity #1: biological sensing at the microbial level25:42 — Opportunity #2: better incentives than today's carbon and biodiversity credits27:15 — Why mycelium materials and food are the "blunt" plays28:41 — Agriculture and restoration: why 80–90% of commercial inoculum is dead on arrival31:17 — Monoculture tree planting, and why about half the trees die within five years34:26 — Funga, the startup that (pun intended) spun out of this science36:56 — Patient capital, hybrid philanthropic-venture funding, and "DARPA for the environment"38:56 — Venture studios built on nature data40:07 — Opportunity #3: supply-chain biodiversity risk and EU reporting41:11 — How to support SPUN: donate, follow along, use the open data42:47 — What gives Jason hope: bringing back Britain's temperate rainforest44:39 — Wrap-upGuest bioJason Cremerius is Managing Director and Chief Strategy Officer of SPUN. He works with founder Toby Kiers and the board to build SPUN into a platform that can scale its impact. For two decades, Jason has built mission-driven organizations that rewire legacy systems to benefit people and the natural world. That work includes: Designing platforms for global enterprisesWorking in corporate venture capitalAdvising startups and investors from day zero through exitCo-founding b.theory ventures, a venture studio that incubates climate startups He's not a scientist by training. He came to fungi five years ago and had to get up to speed fast. He lives in Greenpoint, Brooklyn, right off the G line. About SPUN: SPUN is a science-based nonprofit founded in 2021 to map and protect Earth's mycorrhizal fungal networks. In 2025 it launched the Underground Atlas, published in Nature, the first high-resolution global map of underground fungal biodiversity. It found that more than 90% of fungal biodiversity hotspots lie outside protected areas. Key takeawaysMycorrhizal fungi partner with roughly 90% of land plants. Fungi deliver scarce nitrogen and phosphorus, and plants pay in carbon.About 13 billion tons of CO₂ flows from plants into these fungi each year, roughly a third of fossil fuel emissions. How long that carbon stays in the soil is an open research question SPUN is studying.More diverse fungal communities mean more nutrient trading. In some experiments, well-matched fungal partners made plants up to 64% more productive.Grasslands, not just forests, hold some of the densest fungal networks. They're vulnerable, but they also recover faster when restored.Fungal partnerships are hyper-local. Non-native inoculants, most of which are dead on arrival anyway, don't transfer well. That's a hard problem for markets that want one product to work everywhere.Jason's three investable themes: microbial-scale environmental sensing; nature-based credits that capture real complexity; biodiversity intelligence for corporate supply chains.SPUN's data is open. Entrepreneurs with novel use cases are invited to reach out.Links & resources mentionedSPUN: spun.earthUnderground Atlas: spun.earth/underground-atlasToby Kiers: SPUN founder; 2025 MacArthur Fellow, 2026 Tyler Prize laureateGlobalFungi: the fungal DNA database behind SPUN's baseline modelFunga (founder Colin Averill): fungal inoculants for Southeastern US pine forestsAzolla Ventures: Funga investorGrantham Foundation and Quadrature Climate Foundation: hybrid philanthropic funders mentioned"Mycorrhizal mycelium as a global carbon pool" (Hawkins et al., Current Biology, 2023): the 13-billion-ton studyThe Lost Rainforests of Britain by Guy Shrubsole We're not quite f*d
