The Underground Carbon Economy: How Fungi Trade, Hoard, and Negotiate

Introduction: The Invisible Engine of the Biosphere

For centuries, the prevailing view of the terrestrial biosphere has been decidedly surface-centric. Biological surveys, conservation priorities, and climate models have largely focused on the flora and fauna visible to the naked eye—the canopy of the rainforest, the charismatic megafauna of the savannah, and the agricultural expanses that feed humanity. The soil beneath these landscapes was frequently relegated to the status of an inert substrate, a "black box" of minerals and organic matter that plants passively exploited. This perspective has undergone a radical transformation in the early 21st century, revealing the soil not as a passive medium, but as a dynamic, intelligent, and highly transactional biological marketplace.

In January 2026, this paradigm shift was formally recognized on the global stage when American evolutionary biologist Dr. Toby Kiers was awarded the Tyler Prize for Environmental Achievement. Often described as the "Nobel Prize for the Environment," the award honors Kiers for her transformative research into the hidden world of mycorrhizal fungi—vast, microscopic networks that connect plant roots and facilitate the exchange of nutrients for carbon. Kiers’ work has shattered the romanticized notion of nature as a purely cooperative idyll, replacing it with a rigorous, evidence-based understanding of underground ecosystems as complex economies driven by trade, hoarding, price manipulation, and conflict.

The implications of these discoveries extend far beyond the realm of evolutionary biology. As the global community grapples with the accelerating crises of climate change and biodiversity loss, Kiers’ research has identified the "hidden fungal network" as a critical variable in the planetary equation. With new estimates suggesting that these underground networks sequester approximately 13.12 billion tons of carbon dioxide annually—roughly 36 percent of global fossil fuel emissions—the preservation of fungal biodiversity has emerged as an urgent priority.

This report provides an exhaustive analysis of the scientific breakthroughs led by Dr. Toby Kiers, the advanced methodologies employed to render the invisible visible, and the profound environmental implications of the "Underground Atlas" now mapping the Earth’s subterranean life. Integrating data from recent studies, including landmark papers in Nature and Current Biology, and the launch of the Society for the Protection of Underground Networks (SPUN), we explore how the "microbial majority" is reshaping our understanding of life on Earth.

The Laureate and the Prize: Recognizing the Underground

The Tyler Prize for Environmental Achievement

Established in 1973, the Tyler Prize for Environmental Achievement is one of the oldest and most prestigious international awards in environmental science. It has historically recognized individuals whose work has fundamentally altered our understanding of the natural world or catalyzed major policy shifts. Past laureates include luminaries such as Jane Goodall, Michael Mann, and E.O. Wilson. The awarding of the 2026 prize to Toby Kiers signals a significant institutional pivot: a recognition that the "microbial majority"—the unseen life within the soil—is as critical to planetary health as the visible ecosystems above.

The prize, which carries a cash award of 250,000 USD, specifically cites Kiers for her "pioneering research into hidden fungal networks" and her leadership in the global movement to map and protect underground biodiversity. Rashid Sumaila, chair of the Tyler Prize Executive Committee, described her work as "transformative," highlighting her unique ability to translate complex scientific insights into real-world conservation action through initiatives like SPUN.

A Scientific Evolution: From Panama to Amsterdam

Toby Kiers’ journey into the soil began not in a laboratory, but in the dense, humidity-choked rainforests of Panama. At the age of 19, Kiers secured a grant to join a scientific expedition, where she found herself captivated not by the towering canopy, but by the mechanisms supporting it. Standing beneath massive trees in one of the world's most diverse ecosystems, she began to question the stability of the mutualism between plants and the fungi she knew existed on their roots.

Standard evolutionary theory posits that natural selection favors individuals that maximize their own fitness. Yet, the symbiosis between plants and mycorrhizal fungi appeared to be a form of altruism—a harmonious partnership where two distinct kingdoms of life cooperated for mutual benefit. Kiers questioned how such a system could persist over millions of years without being overrun by "cheaters"—individuals that take resources without providing anything in return.

This skepticism led her to the University of California, Davis, where she earned her PhD, and subsequently to Vrije Universiteit Amsterdam, where she now holds a University Research Chair. Her research has consistently challenged the "communal" view of symbiosis, instead applying economic principles to biological interactions. She hypothesized that if the plant-fungal relationship was stable, it must be governed by mechanisms that punish cheating and reward cooperation—essentially, a biological market.

The Biological Marketplace: Economics Without Brains

One of the central pillars of Kiers' research is the application of "Biological Market Theory" (BMT) to the study of mycorrhizal fungi. Originally developed to explain cooperative behaviors in animal societies—such as grooming partnerships in primates or cleaning services in reef fish—BMT treats the interaction between organisms as an economic exchange of goods and services governed by supply and demand.

The Commodities of the Trade

In the subterranean economy, the currency is elemental.

• The Plant's Currency: Plants, through the miracle of photosynthesis, possess an abundance of carbon. They synthesize sugars and lipids (fats) using energy from the sun.

• The Fungus's Currency: Fungi cannot photosynthesize. However, they possess an expansive, thread-like network of hyphae that can navigate the microscopic pore spaces of the soil. This architecture makes them master scavengers of mineral nutrients, specifically phosphorus and nitrogen, which are often locked in soil forms inaccessible to plant roots.

The trade is simple in principle: the fungus delivers phosphorus and nitrogen to the plant, and in return, the plant delivers carbon to the fungus. However, Kiers’ research demonstrated that this is not a fixed exchange rate. It is a dynamic market where prices fluctuate based on scarcity.

The Mechanism of "Shrewd" Trading

Through a series of elegant experiments using in vitro root organ cultures, Kiers and her team revealed that fungi are "shrewd traders." They do not passively hand over nutrients to any root they encounter. Instead, they actively assess the "value" of their resources relative to the local market conditions.

The research identified several sophisticated behaviors that mimic human economic strategies:

1. Price Discrimination: Fungi can detect differences in the quality of the carbon provided by different host plants. When connected to multiple plants, a single fungal network will preferentially allocate more phosphorus to the plant providing the highest return in carbon (sugar/lipids).

2. Resource Hoarding: Perhaps the most striking finding was the ability of fungi to "hoard" resources to manipulate prices. When phosphorus is abundant in the soil, one might expect the fungus to flood the market, driving the "price" (carbon payment) down. Instead, Kiers found that fungi will sequester phosphorus within their hyphae, releasing it slowly to maintain a high trade value. This behavior creates an artificial scarcity that forces the plant to continue paying a premium for the nutrient.

3. Reciprocal Sanctions: The market is policed by both parties. If a fungus stops providing phosphorus, the plant can cut off the flow of carbon to that specific root section. Conversely, if a plant reduces its carbon payment, the fungus will divert nutrients elsewhere. This system of reciprocal rewards and sanctions is what stabilizes the evolutionary relationship, preventing cheaters from destabilizing the network over deep time.

Biochemical Banking: Polyphosphates

To execute these trade strategies, fungi utilize specific biochemical mechanisms to store and transport nutrients. Research indicates that fungi accumulate phosphorus in the form of polyphosphates—long chains of phosphate molecules—within their hyphae. These polyphosphate reserves act as a "bank account," allowing the fungus to buffer against fluctuations in soil nutrient availability.

By converting inorganic phosphate into polyphosphate granules, the fungus essentially removes the nutrient from the immediate "market," storing it for future leverage. This mechanism allows the fungus to move resources from areas of abundance (rich soil patches) to areas of scarcity (nutrient-poor zones), engaging in a form of spatial arbitrage that maximizes their carbon revenue.

Advanced Methodologies: Rendering the Invisible Visible

The primary obstacle in studying underground fungal networks has historically been their opacity. Soil is a complex, opaque matrix; digging it up to see the fungi destroys the very networks researchers wish to study. To overcome this, Kiers and her team at Vrije Universiteit Amsterdam, in collaboration with the Amsterdam Biophysics Institute (AMOLF), have developed cutting-edge technologies to bypass the physical limitations of soil research.

Robotic Imaging Systems

To observe the architecture and behavior of these networks without disturbance, Kiers’ lab developed a high-throughput robotic imaging system. This platform allows researchers to monitor fungal behavior in real-time over extended periods.

• Real-Time Visualization: The system captures high-resolution images of fungal networks as they grow, branch, and explore their environment.

• Dynamic Flow: The imagery reveals a dynamic, pulsing system. Cytoplasm and nutrients stream through the hyphae, redirecting flows in response to local stimuli. This "high-resolution" view has been instrumental in debunking the static view of soil fungi, showing instead a responsive, decision-making entity that constantly reconfigures itself to optimize resource acquisition.

Quantum Dot Tracking: Nanoprobes in the Soil

Perhaps the most significant technical breakthrough is the use of "quantum dots" to track nutrient flow. Quantum dots are nanoscale semiconductor particles that fluoresce with high brightness and stability when exposed to specific wavelengths of light.

Kiers and her team developed a technique to tag nutrients—specifically apatite, a rock phosphate source—with these fluorescent nanoparticles.

• The Methodology: By introducing these tagged nutrients to a fungal network connecting two different plant roots (one "rich" in carbon, one "poor"), the researchers could visually track the movement of individual phosphorus packets through the hyphae.

• The Findings: Using confocal microscopy and raster image correlation spectroscopy, the team observed the fungi moving the quantum-dot-tagged phosphorus across the network. The tracking revealed that the fungi did not distribute nutrients evenly. They preferentially allocated the tagged phosphorus to the host that offered the best carbon return. Furthermore, the fungi were observed moving phosphorus away from "poor" hosts toward "rich" hosts, effectively stripping resources from one area to invest them in a more profitable partner. This provided the first direct visual evidence of inequality management in fungal networks.

The Global Carbon Footprint of Fungi: The 13 Billion Ton Question

While the behavioral economics of fungi are fascinating at the microscopic scale, their aggregate impact on the planetary scale is staggering. Kiers’ work has been pivotal in quantifying the role of mycorrhizal fungi in the global carbon cycle, moving the field from theoretical assumptions to hard data.

The Hawkins et al. (2023) Study

A landmark study co-authored by Kiers and published in Current Biology (Hawkins et al., 2023) provided a comprehensive global estimate of carbon allocation from plants to mycorrhizal fungi. The research team analyzed nearly 200 datasets to trace carbon flow through the biosphere, calculating exactly how much of the carbon fixed by plants during photosynthesis ends up in the fungal network.

The Findings:

• Total Allocation: The study estimated that global plant communities allocate approximately 13.12 gigatons of carbon dioxide equivalents (CO2e) per year to mycorrhizal fungi.

• Contextualizing the Number: To put this in perspective, 13.12 billion tons is roughly equivalent to 36 percent of annual global fossil fuel emissions. It is more than the total annual emissions of China (approx. 12.47 billion tons) and nearly three times the annual emissions of the United States.

• Breakdown by Fungal Type:

• Arbuscular Mycorrhizal (AM) Fungi: Receive ~3.93 Gt CO2e/year. These fungi dominate grasslands, tropical forests, and most agricultural crops.

• Ectomycorrhizal (EcM) Fungi: Receive ~9.07 Gt CO2e/year. These fungi are primarily associated with woody plants in temperate and boreal forests.

• Ericoid Mycorrhizal (ErM) Fungi: Receive ~0.12 Gt CO2e/year. These are found in heathlands and tundra ecosystems.

The Mycelial Sink

This massive transfer of carbon is not merely a "pass-through." A significant portion of this carbon is used to build fungal biomass—the mycelium itself. Fungi are composed of carbon-rich polymers such as chitin and beta-glucans. When fungal hyphae die, they leave behind "necromass," which becomes a stable component of soil organic matter.

Furthermore, mycorrhizal fungi produce compounds like glomalin (a glycoprotein), which acts as a "super glue" for soil aggregates. These aggregates protect organic carbon from oxidation by bacteria, effectively locking it in the soil for decades or centuries. The study suggests that the "mycorrhizal mycelium" is a global carbon pool of significance comparable to oceanic sinks or above-ground forest biomass, yet it has been largely omitted from standard climate models.

Table 1: Comparative Carbon Flux Analysis

Data derived from Hawkins et al. (2023).

Carbon Sink / Source	Estimated Annual Flux (Gt CO2e)
Global Fossil Fuel Emissions (2021)	~36.3
Allocation to Mycorrhizal Fungi	~13.1
China's Annual Emissions (2021)	~12.5
US Annual Emissions (2021)	~4.7
EcM Fungi Allocation	~9.07
AM Fungi Allocation	~3.93

SPUN and the Underground Atlas: Mapping the Unknown

Despite their critical importance, underground ecosystems are woefully under-protected. Conservation priorities have traditionally been determined by above-ground flora and fauna, leading to a massive gap in the protection of soil biodiversity. To address this, Toby Kiers co-founded the Society for the Protection of Underground Networks (SPUN), a non-profit scientific research organization dedicated to mapping and preserving fungal biodiversity.

The Protection Gap

SPUN’s initial analyses revealed a concerning reality: the majority of the world's underground biodiversity hotspots are not located within existing protected areas.

• AM Fungi: Only 5.1 percent of Arbuscular Mycorrhizal hotspots are currently protected.

• EcM Fungi: Only 13.9 percent of Ectomycorrhizal hotspots are protected.

• Overall: Approximately 90 percent of diverse underground fungal systems lack formal conservation status.

This disconnect arises because the distribution of fungal biodiversity does not perfectly overlap with plant biodiversity. For example, high-latitude boreal forests may have lower plant diversity but massive ectomycorrhizal fungal diversity. Similarly, arid grasslands often host rich communities of AM fungi that are critical for soil stability but are overlooked by conservation schemes focused on "lush" vegetation.

The Underground Atlas

To guide conservation efforts, SPUN launched the Underground Atlas, the first high-resolution global map of mycorrhizal fungal biodiversity.

Methodology:

The Atlas utilizes a combination of "big data" and machine learning to predict fungal distribution.

1. Data Collection: The team aggregated over 2.8 billion fungal DNA sequences from 25,000 soil samples collected across 130 countries. This represents the largest dataset of fungal DNA ever assembled.

2. Machine Learning: Using these inputs, they trained ensemble machine-learning models to analyze relationships between fungal diversity and environmental variables, including climate, soil chemistry, vegetation type, and topography.

3. Prediction: The algorithms generate spatial predictions of fungal richness and endemism at a resolution of 1 square kilometer for the entire planet. This high-resolution mapping allows conservationists to identify specific plots of land that are critical for fungal biodiversity.

Findings and Hotspots:

The Atlas has identified unexpected hotspots of fungal diversity. Key areas include:

• The Grasslands of the Kazakhstan Steppes: A region often overlooked in conservation but rich in AM fungi.

• The Tropical Conifer Forests of Northern Mexico: A hotspot for fungal endemism.

• The Coastal Scrublands of Ghana: A global hotspot for arbuscular mycorrhizal biodiversity. This region is of particular concern because it faces severe erosion rates of two meters per year due to climate change and rising sea levels. SPUN has identified this as a priority zone for "salvage biology"—documenting and preserving the genetic diversity before it is lost to the ocean.

Table 2: SPUN Underground Atlas Specifications

Data derived from SPUN technical documentation.

Component	Specification	Purpose
Input Data	2.8 billion DNA sequences	Comprehensive genetic inventory of soil life
Sample Size	25,000 soil samples	Physical verification of fungal presence (Ground Truthing)
Geographic Scope	130 countries	Global representation of ecoregions
Resolution	1 km² (30 arc seconds)	High-precision mapping for local conservation
Output Metrics	Richness, Endemism, Uncertainty	Identifying hotspots and data-poor regions

Theoretical Divergences: The "Wood Wide Web" vs. The Marketplace

The popularization of mycorrhizal networks is often associated with the term "Wood Wide Web," coined in relation to the work of forest ecologist Suzanne Simard. Simard’s work emphasized the cooperative, almost altruistic nature of these networks, describing "Mother Trees" that nurture seedlings through fungal connections. While Kiers acknowledges the connectivity, her "Biological Market" perspective offers a more nuanced, and sometimes divergent, interpretation.

Altruism vs. Self-Interest

• Simard’s "Mother Tree" Hypothesis: Focuses on the role of the network in facilitating resource sharing and ecosystem cohesion. Trees are seen as sending warning signals and nutrients to neighbors, suggesting a "socialist" forest where the strong help the weak.

• Kiers’ "Market" Hypothesis: Focuses on conflict, trade, and individual fitness. Kiers argues that if networks were purely altruistic, they would be unstable over evolutionary time. Her research suggests that stability is maintained by the active policing of "fair trade." For example, Kiers notes that while trees do transfer carbon to fungi, if a fungus connects a tree to a rival plant species, the tree might reduce investment in that specific fungal strain to avoid subsidizing a competitor.

This "dark side" of the symbiosis—where orchids steal carbon from trees ("mycoheterotrophy") and plants engage in underground warfare—is central to understanding the evolutionary resilience of the system. Kiers’ perspective aligns the fungal world with standard evolutionary theory, where individual fitness drives behavior, even if the emergent result appears cooperative. The network is not a commune; it is a competitive economy where cooperation is purchased with commodities.

Conservation and Policy: The "Underground Advocates"

Coinciding with the Tyler Prize announcement, SPUN launched the "Underground Advocates" program, a new initiative developed in partnership with New York University (NYU) Law’s "More-than-Human-Life" (MOTH) program. This initiative aims to bridge the gap between scientific discovery and legal protection.

Bridging Science and Law

The Underground Advocates program equips local scientists and communities in biodiversity hotspots with the legal and policy tools necessary to advocate for the protection of their soil systems. The goal is to translate complex fungal datasets—like those from the Underground Atlas—into actionable legal frameworks.

• Legal Personhood: The program explores legal concepts that could extend rights or protections to "funga" (flora, fauna, and funga), similar to the "Rights of Nature" movements that have granted legal personhood to rivers and mountains in some jurisdictions.

• Policy Integration: Kiers hopes to integrate fungal biodiversity into international treaties and national conservation strategies. Currently, most Environmental Impact Assessments (EIAs) completely ignore soil biodiversity. The Advocates program aims to make fungal surveys a mandatory component of land-use planning and development projects.

Conclusion: The Library of Solutions

The recognition of Toby Kiers with the 2026 Tyler Prize is not just a career achievement; it is a signal of the urgent need to integrate soil science into climate policy. As the world faces the dual crises of climate change and biodiversity loss, the "hidden fungal" world offers a "library of solutions."

Understanding which fungal species are the most efficient at sequestering carbon is the next frontier. Kiers' research suggests that we could potentially "manipulate" the plant-fungal market to support sustainable agriculture and enhance carbon drawdown. By identifying and encouraging fungal strains that demand less carbon for their own respiration and store more in recalcitrant soil forms, humanity could theoretically boost the carbon storage capacity of forests and agricultural lands.

However, this potential relies on the preservation of the existing genetic diversity. The Underground Atlas serves as a roadmap for this preservation, highlighting the regions where ancient fungal networks are most threatened by industrial agriculture, urbanization, and climate change.

Toby Kiers’ work has stripped away the soil's anonymity. Through her eyes, the ground beneath us is revealed not as dirt, but as a bustling, high-stakes marketplace of interspecies commerce that sustains the terrestrial biosphere. As the recipient of the "Environmental Nobel," her message is clear: the future of life above ground depends on the protection of the networks that bind the world together from below. The "hidden fungal" is hidden no more; it is now recognized as the invisible engine of the biosphere.

Bibliography

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  • Context: Supports the "13.12 billion tons" (13.12 Gt) carbon sequestration figure and the breakdown by fungal type (AM/EcM) cited in the "Global Carbon Footprint" section.

  • Accession Date: January 19, 2026

  • URL: https://www.cell.com/current-biology/fulltext/S0960-9822(23)00593-5

• Reciprocal Rewards Stabilize Cooperation in the Mycorrhizal Symbiosis

  • Context: The seminal paper by Dr. Toby Kiers establishing the "Biological Market Theory" in fungi, proving that they punish "cheaters" and trade based on value.

  • Accession Date: January 19, 2026

  • URL: https://www.science.org/doi/10.1126/science.1208473

• Mycorrhizal Fungi Respond to Resource Inequality by Moving Phosphorus from Rich to Poor Patches across Networks

  • Context: Supports the "Advanced Methodologies" section regarding the use of Quantum Dots (nanoparticles) to track nutrient flow and the behavior of moving resources to "rich" hosts.

  • Accession Date: January 19, 2026

  • URL: https://www.cell.com/current-biology/fulltext/S0960-9822(19)30490-8

• Society for the Protection of Underground Networks (SPUN) – Mission & Atlas

  • Context: Supports the section on the launch of SPUN, the "Underground Atlas," and the protection gap statistics (only ~5-14% of hotspots protected).

  • Accession Date: January 19, 2026

  • URL: https://spun.earth/

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  • Accession Date: January 19, 2026

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