The Underground Blueprint: How Mycorrhizal Fungi Could Restore the World’s Forests

According to THE GUARDIAN

Beneath the Forest Floor: A Hidden Infrastructure

If you walk through Ballachuan hazelwood in Scotland, the last thing you might imagine is that the forest’s lifeblood runs beneath your feet. The landscape—quiet, moss-draped, and seemingly eternal—hides a subterranean circulatory system woven by fungi. These are the mycorrhizal fungi: microscopic threads that entangle themselves with roots, creating an underground superhighway for nutrients, water, and communication.

For centuries, conservation focused on what we could see: towering trees, charismatic animals, birdsong, and canopy cover. But now, as global rewilding efforts gather pace, scientists argue we’ve missed half the picture. Without fungi, restoration risks becoming a façade—a forest without the foundations it needs to thrive.

The Society for the Protection of Underground Networks (SPUN) has embarked on a mission to map these fungal systems. In the words of SPUN director Toby Kiers, “We’ve mapped oceans, mountains, forests, and even galaxies. But the fungal networks beneath our feet—the very structures that sustain land life—have remained invisible.”

That invisibility may soon end.

The SPUN Initiative: Making the Invisible Visible

SPUN’s project combines cutting-edge DNA sequencing, machine learning, and ecological surveys to chart fungal diversity worldwide. In Scotland’s ancient hazelwood groves, researchers collect soil samples to decode the mycorrhizal networks that tether tree roots together. Each sample reveals fragments of fungal DNA, which scientists then assemble into maps of biodiversity.

This work is part of a larger global project that includes sites in Colombia’s rainforests and Palmyra Atoll in the Pacific. By building a “global atlas” of fungi, SPUN aims to identify where fungal diversity is thriving—and where it is dangerously unprotected.

The findings so far are sobering: less than 10% of the world’s underground biodiversity hotspots lie within protected areas. That means agriculture, development, and climate change threaten the fungal lifelines of our ecosystems.

Why Mycorrhizal Fungi Matter

To understand why mapping matters, one must first understand the fungi themselves. Mycorrhizal fungi form symbiotic relationships with over 80% of plant species. Through this partnership:

• Nutrients flow both ways: Plants trade carbon (sugars) with fungi, who in return supply phosphorus, nitrogen, and other vital nutrients.
• Water security: Fungi extend root systems, acting like underground pipelines that draw water from distant soil.
• Disease defense: Fungi can signal threats and bolster plant immune systems.
• Carbon storage: These networks help sequester billions of tons of carbon in soils each year, stabilizing global climate.

Without these fungal systems, forest restoration often fails. A sapling planted without its fungal partner is like a heart without arteries—it might survive, but it cannot flourish.

Lessons from Britain’s Temperate Rainforests

The UK once hosted lush temperate rainforests, now reduced to fragments. Restoration groups are replanting native trees, but early efforts overlooked fungi. Seedlings introduced without local fungal inoculation frequently died or grew poorly.

Recent pilot projects changed strategy: introducing native mycorrhizal spores alongside saplings. The results? Dramatically higher survival rates, stronger growth, and more resilient ecosystems. These examples underscore SPUN’s warning: above-ground conservation is incomplete without underground restoration.

Global Implications: From Tropics to Tundra

SPUN’s maps highlight two dominant fungal groups with distinct global patterns:

• Arbuscular mycorrhizal fungi thrive in equatorial regions, mirroring biodiversity patterns of tropical plants and animals.
• Ectomycorrhizal fungi peak in northern latitudes, especially boreal forests, and parts of Australia and South America.

Together, they form the backbone of the “wood wide web,” enabling plant communities to share resources across landscapes.

In the Amazon, fungal networks sustain rainforest resilience. In boreal forests, they help store carbon in permafrost soils. Yet both are at risk as climate change accelerates.

Climate Change and Fungal Vulnerability

Fungal maps also illuminate a grim reality: climate change is unraveling underground biodiversity. Ghana’s coastal regions host extraordinary fungal diversity, but rising seas and erosion are erasing these ecosystems. Deforestation in Brazil’s Cerrado and logging in Tasmania likewise threaten hotspots.

The irony is sharp: these fungi help buffer ecosystems against climate change, yet climate change itself endangers them. Without urgent action, we risk a cascading feedback loop—fungal loss weakens forests, weakened forests absorb less carbon, and global warming accelerates.

Conservation Beyond the Canopy

For too long, conservation has focused on visible life—charismatic megafauna and majestic landscapes. SPUN argues for a paradigm shift: fungi must be included in restoration targets and biodiversity strategies.

Michael Van Nuland, SPUN’s lead data scientist, puts it bluntly: “Food security, water cycles, and climate resilience all depend on safeguarding these underground ecosystems.”

That means:

• Designing restoration projects that include fungal inoculation.
• Protecting soil from heavy tilling, pesticides, and deforestation.
• Mapping fungal hotspots as conservation priorities alongside forests and coral reefs.

Ethical and Practical Challenges

Restoring fungal communities is not simple. Introducing foreign fungi can disrupt native systems, creating ecological imbalances. Ethical restoration emphasizes working with local fungi, cultivated from nearby soils.

Moreover, fungal diversity often exists only as DNA fragments—species we cannot yet name or culture. This raises challenges in conservation: how do you protect what you cannot fully see?

A Blueprint for the Future

Despite challenges, fungal mapping is already transforming restoration practices. From Britain’s hazelwoods to African savannas, fungal data provides concrete restoration blueprints.

Rebecca Shaw of WWF summarizes: “Mycorrhizal fungi need to be recognized as a priority in the library of solutions to biodiversity loss, climate change, and food insecurity.”

By turning the invisible into maps, SPUN gives policymakers, conservationists, and communities the tools to reimagine restoration—not as tree-planting alone, but as rebuilding entire symbiotic systems.

Conclusion: Rising to the Challenge

Humanity’s survival is tied to forests, and forests’ survival is tied to fungi. Mycorrhizal networks are not just biological curiosities—they are the infrastructure of life itself.

For centuries, we overlooked them. Now, with maps in hand and urgency at our backs, we have the chance to correct that blindness. Forest restoration can no longer be just about what we see above ground. It must embrace the invisible threads that bind ecosystems together.

If the 20th century was the age of mapping human frontier—oceans, space, genomes—the 21st may be the age of mapping fungal frontiers. Only then can we rebuild forests that are truly alive, rooted in both soil and symbiosis.

References

SPUN. Society for the Protection of Underground Networks.

WWF. Biodiversity solutions

According to THE GUARDIAN

Frequently Asked Questions

How do mycorrhizal fungi help forests recover?

Mycorrhizal fungi are foundational to forest ecosystem recovery and cannot be separated from tree restoration efforts—they function as the essential infrastructure through which forest trees access nutrients, water, and biotic support. Role of mycorrhizal fungi in forest recovery: nutrient acquisition—forest soils recovering after disturbance (logging, fire, mining, deforestation) often have disrupted nutrient cycles; mycorrhizal hyphae extend far beyond tree roots, accessing phosphorus, nitrogen, and micronutrients in small soil pores that roots cannot enter; without mycorrhizal partners, recovering trees experience severe nutrient limitation even when soil nutrient pools are adequate. Water uptake enhancement—mycorrhizal networks access soil water in pores too small for roots; during drought stress (common in recovering forests exposed to increased solar radiation and evaporation), mycorrhizal trees are dramatically more drought-tolerant than non-mycorrhizal trees. Pathogen protection—mycorrhizal fungi physically coat root surfaces (in ECM systems, the Hartig net and mantle), excluding pathogenic fungi; mycorrhizal communities also produce antifungal compounds that suppress root pathogens in the rhizosphere. Carbon networks and seedling establishment—in recovering forests, large established trees (‘mother trees’) connected to new seedlings via mycorrhizal networks can supply fixed carbon to seedlings in low-light understory conditions; this inter-tree carbon transfer may be critical for understory seedling establishment in some forest types. Soil structure improvement—mycorrhizal hyphae and their secretion of glomalin (in AM systems) improve soil aggregate stability, water infiltration, and resistance to erosion during the vulnerable early recovery period.

What is the difference between arbuscular and ectomycorrhizal fungi in forest restoration?

The distinction between arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi is fundamental to forest restoration planning because tree species obligately associate with one guild or the other, and the ecological niches, biodiversity, and conservation status of these two groups differ substantially. Ectomycorrhizal (ECM) fungi: distribution—ECM associations dominate temperate and boreal forests; important ECM tree genera include Pinus, Picea, Quercus, Fagus, Betula, Alnus, Populus, Salix, and Dipterocarpaceae (dominant in tropical Asian forests). Fungal diversity—ECM fungi belong to numerous taxonomic orders including Agaricales (chanterelles, boletes, webcaps), Boletales, Russulales, Thelephorales, and others; include most familiar forest mushroom fruiting bodies; highly diverse (tens of thousands of species globally). Ecology—typically host-specific to some degree; some ECM species associate with only one or a few tree genera; ECM fungal communities can be slow to establish from spores on restoration sites distant from intact ECM forests; ECM fungi are less likely to persist in degraded soils than AM fungi. Arbuscular mycorrhizal (AM) fungi: distribution—AM associations are the ancestral and most widespread mycorrhizal type; found in tropical forests, grasslands, most agroecosystems, and a majority of plant species globally; important in tropical forest restoration where most pioneer and climax trees are AM-associated. Fungal diversity—AM fungi all belong to the phylum Glomeromycota; only approximately 250–300 species described globally; much lower diversity than ECM fungi. Ecology—AM fungi form an extensive spore bank in most soils and colonise new roots rapidly; generally more resilient to soil disturbance than ECM fungi; restoration challenge is more often about ECM establishment than AM establishment for many tree species.

Should commercial tree planting programs include mycorrhizal inoculation?

Evidence from forest restoration research strongly supports mycorrhizal inoculation of nursery stock for many restoration contexts, though cost-benefit considerations and ecological matching are critical to effective implementation. Evidence for inoculation benefits: survival and growth—controlled experiments and field trials consistently show that mycorrhizally inoculated seedlings have higher survival rates and faster growth than uninoculated seedlings on degraded restoration sites; effect sizes are largest when the restoration site lacks appropriate spore banks (severely degraded soils, mined soils, agricultural land being converted to forest). Phosphorus-limited soils—on phosphorus-limited soils (most tropical soils and many temperate forest soils), mycorrhizal inoculation produces the largest growth benefits, with inoculated seedlings often growing 2–5× faster than uninoculated counterparts. When inoculation is most needed—and when it may be less critical: high-priority inoculation contexts: ecological restoration on severely degraded land (mine rehabilitation, intensive agricultural land being reforested); ECM tree species in sites far from intact ECM forest (no natural spore sources); when rapid establishment is critical (e.g., for erosion control). Contexts where inoculation may be less critical: restoration sites adjacent to intact forest (natural spore sources available through wind dispersal or hyphal growth); AM-associated tree species on sites with intact soil profiles (AM fungi are more resilient and usually present in soil spore banks). Large-scale planting programs: the trillion tree initiatives and national reforestation programs often do not include mycorrhizal inoculation due to cost and logistical complexity; this is a significant shortcoming that may undermine long-term reforestation success; advocacy for integrating mycorrhizal inoculation protocols into national reforestation programs is a priority in the forest ecology research community.

Can forests restore themselves naturally without human intervention?

Natural forest regeneration (passive restoration or ‘forest recovery’) is one of the most ecologically sophisticated and often undervalued restoration approaches—and mycorrhizal fungal recovery is a key component of why passive regeneration often succeeds where active planting fails. Evidence for natural regeneration’s effectiveness: speed of recovery—in many tropical and subtropical contexts, passive regeneration on abandoned agricultural land or logged forest produces impressive recovery within 20–40 years in terms of tree species diversity, canopy cover, and above-ground carbon; a landmark meta-analysis (Chazdon et al., 2016, Science Advances) found that passive regeneration in tropical regions recovers 78–122% of primary forest biodiversity within 40 years. Cost comparison—passive regeneration is dramatically cheaper than active planting; on suitable sites, allowing natural regeneration is the most cost-effective restoration approach by a wide margin. When passive regeneration succeeds and when it fails: conditions for success: seed sources present in adjacent intact or recovering forest; appropriate mycorrhizal inoculum present in soil or in proximity; absence of aggressive invasive species that prevent forest tree establishment; cessation of the original disturbance (farming, grazing). Conditions requiring active intervention: seed sources have been locally eliminated (most tree species extinct from the landscape); soils have been severely degraded (mining, high-erosion land); invasive species actively prevent tree establishment; mycorrhizal communities have been eliminated (intensive soil sterilisation, long cultivation history). Mycorrhizal implications: passive regeneration succeeds partly because natural seed input arrives with mycorrhizal inoculum (spores on seed coats, in attached soil); abandoned farmland often retains some AM fungal spore bank; proximity to intact ECM forest provides ECM spore sources. Active planting often fails partly because transplanted seedlings arrive without established mycorrhizal partnerships and encounter degraded mycorrhizal communities.

How does mycorrhizal health affect climate change and carbon storage?

Mycorrhizal fungi are central to the carbon dynamics of forest ecosystems and their role in climate change regulation is increasingly recognised in ecological and policy discussions. Mycorrhizal fungi and carbon cycling: forest carbon storage is critically dependent on tree health and growth, which depends on mycorrhizal function—healthy mycorrhizal networks enable trees to grow faster and store more carbon in wood and roots. Direct soil carbon contribution—mycorrhizal fungi contribute substantially to soil carbon pools through their biomass and secretions; glomalin from AM fungi is a major component of stable soil organic carbon (estimated to represent up to 27% of total soil carbon in some grassland and forest soils); ECM fungal necromass (dead hyphal material) is a major input to deep soil carbon pools. Nitrogen and phosphorus limitation on carbon storage: forests’ capacity to store additional carbon under elevated CO₂ (the ‘CO₂ fertilisation effect’) is strongly limited by nitrogen and phosphorus availability; mycorrhizal nutrient acquisition enables trees to grow more rapidly in elevated CO₂ conditions; modelling studies suggest that mycorrhizal network capacity will determine whether forests can act as net carbon sinks under climate change scenarios. ECM vs. AM forests and carbon dynamics: ECM-dominated forests (boreal, temperate) tend to have higher soil carbon accumulation than AM-dominated forests; ECM fungi produce organic nitrogen-mining enzymes that access organic nitrogen in stable soil organic matter, protecting soil carbon from microbial decomposition; AM fungi do not have these nitrogen-mining capabilities, leading to more rapid soil carbon turnover in AM-dominated tropical forests; climate change that shifts the geographic ranges of ECM vs. AM tree species could alter global carbon storage dynamics significantly.