Report on the Global Distribution and Conservation Status of Mycorrhizal Fungi

Executive Summary

Mycorrhizal fungi are critical ecosystem engineers, essential for sustaining plant life and regulating global biogeochemical cycles, thereby directly supporting the achievement of Sustainable Development Goal 15 (Life on Land) and SDG 13 (Climate Action). Despite their importance, a significant knowledge gap exists regarding their global biodiversity distribution, which impedes effective conservation and monitoring. This report summarizes a global-scale analysis that utilized machine-learning algorithms trained on over 2.8 billion fungal DNA sequences from 25,000 soil samples to map the richness and rarity of arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) fungi. The findings reveal distinct biogeographical patterns and identify key biodiversity hotspots. Critically, the analysis indicates that less than 10% of these vital mycorrhizal richness hotspots are located within currently protected areas, highlighting a major shortfall in global conservation efforts and a significant challenge to meeting the Kunming-Montreal Global Biodiversity Framework targets. These results provide an essential baseline for prioritizing conservation, guiding sustainable land management in line with SDG 12 (Responsible Consumption and Production), and developing nature-based climate solutions.

Introduction: The Unseen Foundation of Terrestrial Ecosystems and the SDGs

Mycorrhizal fungi form symbiotic relationships with over 80% of plant species, creating vast underground networks that are fundamental to the functioning of Earth’s terrestrial ecosystems. These networks are vital for nutrient cycling and are estimated to facilitate the annual allocation of 3.6 billion tons of carbon from plants into the soil, a process central to SDG 13 (Climate Action). The health and diversity of these fungal communities underpin soil fertility, which is crucial for global food systems and achieving SDG 2 (Zero Hunger).

However, our understanding of the global distribution of this belowground biodiversity lags significantly behind that of plants and animals. This knowledge gap presents a major obstacle for conservation policy, which often relies on aboveground metrics. As this report will demonstrate, patterns of plant diversity are not reliable proxies for the diversity of their mycorrhizal partners. This mismatch means that current conservation strategies may fail to protect a huge component of Earth’s biodiversity, jeopardizing the integrity of ecosystems and the achievement of SDG 15 (Life on Land).

Methodology: A Global Census of Underground Biodiversity

To address the knowledge gap, this study employed a robust analytical framework built on international scientific collaboration, embodying the principles of SDG 17 (Partnerships for the Goals).

1. Data Compilation: The analysis was based on a comprehensive global dataset of nearly 25,000 geolocated soil samples from 130 countries, comprising over 2.8 billion fungal DNA sequences. Data was aggregated from the GlobalFungi, GlobalAMFungi, and Global Soil Mycobiome consortium databases.
2. Machine-Learning Models: Random forest machine-learning algorithms were trained using this data to predict the global richness (number of species) and rarity (endemism-weighted richness) of the two dominant mycorrhizal types: arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) fungi.
3. Spatial Prediction: The models generated high-resolution (1 km²) global maps, identifying key reservoirs of fungal biodiversity and allowing for an assessment of their protection status.
4. Uncertainty Analysis: Rigorous uncertainty and extrapolation analyses were conducted to ensure the responsible interpretation of the predictive maps, providing a transparent tool for policymakers.

Key Findings: Global Patterns and Conservation Gaps

1. Contrasting Global Diversity Patterns

The study revealed distinct and contrasting latitudinal diversity gradients for the two major types of mycorrhizal fungi, underscoring that a one-size-fits-all approach to conservation is inadequate for protecting belowground life.

• Arbuscular Mycorrhizal (AM) Fungi: Predicted richness was highest in ecosystems near the equator and declined towards the poles, following the classical latitudinal diversity gradient. This pattern emphasizes the immense, yet under-appreciated, fungal biodiversity in tropical regions, which are critical for achieving SDG 15.
• Ectomycorrhizal (EcM) Fungi: Predicted richness showed an inverse latitudinal gradient, with the most species-rich communities found in northern temperate and boreal latitudes, as well as in southern temperate regions.

2. Identification of Biodiversity Hotspots

Global hotspots, defined as the top 5% of predicted richness and rarity values, were identified as priority areas for conservation.

• AM Fungal Hotspots: Major hotspots for both richness and endemicity were predicted in the savannas of the Brazilian Cerrado, tropical forests across Southeast Asia, and the Guinean forests of West Africa. Endemicity was particularly high in the Congo and eastern Amazon basins.
• EcM Fungal Hotspots: Richness hotspots were concentrated in northern forest ecosystems, including Siberian and Canadian boreal forests and temperate forests in North America and Europe. In contrast, rarity hotspots were identified in tundra ecosystems and mountainous regions in the tropics and southern hemisphere, such as the Andes and the mountains of Central America.

3. Critical Shortfall in Protected Areas

A central finding of this report is the severe under-protection of mycorrhizal fungal biodiversity, which threatens global targets for nature conservation.

• Globally, only 9.5% of mycorrhizal richness hotspots are located within protected areas. This includes just 5.1% of AM hotspots and 13.9% of EcM hotspots.
• This level of protection is drastically lower than for plants (27%) and vertebrates (33–41%), revealing a critical bias in current conservation planning.
• The finding demonstrates that the world is far from achieving the Kunming-Montreal Global Biodiversity Framework’s “30 by 30” target for this hidden kingdom of life, a cornerstone of implementing SDG 15.
• Furthermore, the stringency of protection is often low. For AM fungi, over 70% of protected hotspots fall under the least-strictly preserved IUCN management categories (V, VI, or unassigned).

4. Key Environmental Drivers of Fungal Diversity

The models identified key environmental factors that shape fungal biodiversity, providing insights for targeted management strategies.

• Climate: Temperature was a primary predictor for both fungal types, directly linking their distribution to the challenges of SDG 13 (Climate Action). Higher temperatures predicted greater AM richness but lower EcM richness.
• Soil Carbon: Soil organic carbon was strongly associated with higher EcM richness, highlighting the synergistic relationship between these fungi and carbon sequestration, a key nature-based solution for climate mitigation.
• Human Land Use: Anthropogenic land cover was a positive predictor of AM fungal richness. This may reflect the proliferation of disturbance-tolerant species, signaling a potential homogenization of fungal communities and reinforcing the need for sustainable land management practices under SDG 12 and SDG 15.
• Aboveground Biomass: Forest biomass was the top predictor for EcM richness and rarity, confirming the tight link between healthy, high-biomass forests and their belowground fungal partners.

Implications for Sustainable Development Goals

The results of this analysis have profound implications for global sustainability policy. Explicitly incorporating mycorrhizal fungi into conservation and land management frameworks is essential for meeting multiple SDGs.

• SDG 15 (Life on Land): To halt biodiversity loss, conservation policies must look belowground. The maps produced in this study provide a tool to identify priority areas for fungal conservation, helping to ensure the “30 by 30” target is meaningful for all biodiversity.
• SDG 13 (Climate Action): Protecting and restoring ecosystems with high EcM fungal diversity, particularly high-biomass forests, is a direct, nature-based strategy to enhance soil carbon sequestration and build climate resilience.
• SDG 2 (Zero Hunger) & SDG 12 (Responsible Consumption and Production): Understanding the distribution of AM fungi, which dominate agricultural lands, can inform soil management practices that enhance crop nutrition and reduce reliance on chemical fertilizers, promoting sustainable agriculture.
• SDG 17 (Partnerships for the Goals): This research demonstrates the power of global data-sharing and collaboration. Further progress requires continued international efforts to fill data gaps, especially in under-sampled tropical and tundra regions.

Conclusion and Recommendations

Mycorrhizal fungi form a hidden, globally significant reservoir of biodiversity that is foundational to the health of terrestrial ecosystems and the delivery of critical ecosystem services. This report reveals that this vital component of life on Earth is severely under-protected, with its diversity hotspots largely overlooked by current conservation agendas.

To align global efforts with the Sustainable Development Goals, the following actions are recommended:

1. Integrate Belowground Data into Conservation Planning: National and international bodies must use maps of fungal diversity, like those presented here, to inform the designation and management of protected areas to meet SDG 15 targets.
2. Establish Monitoring Benchmarks: The global maps provide a baseline for setting monitoring benchmarks to track the status of fungal biodiversity and the effectiveness of conservation and restoration actions over time.
3. Develop Targeted Land-Management Strategies: Land-use policies should be designed to protect and maintain reservoirs of mycorrhizal diversity, supporting goals for sustainable forestry, agriculture, and climate mitigation (SDG 12, SDG 13, SDG 15).
4. Prioritize Research in Data-Poor Regions: International collaborative efforts (SDG 17) should focus on sampling in underrepresented regions to improve model accuracy and uncover new hotspots of fungal diversity.

By explicitly considering the world beneath our feet, we can implement more holistic and effective strategies to protect Earth’s biodiversity, combat climate change, and build a sustainable future for all.

1. SDGs Addressed in the Article

SDG 15: Life on Land

• The article is fundamentally about understanding and conserving terrestrial biodiversity, specifically the “largely hidden component of Earth’s underground ecosystems.” It focuses on mapping the global distribution of mycorrhizal fungi to “monitor and protect key underground ecosystems.”
• It directly addresses the degradation of natural habitats and the loss of biodiversity by highlighting that “less than 10% of predicted mycorrhizal richness hotspots currently exist in protected areas.”
• The research aims to inform conservation policy, stating its results “can help identify conservation priorities, set monitoring benchmarks and create specific restoration plans and land-management strategies,” which is central to SDG 15.
• The article explicitly mentions the Kunming–Montreal Global Biodiversity Framework and its “30 × 30 target goals,” linking the research directly to global conservation efforts.

SDG 13: Climate Action

• The article establishes a clear link between mycorrhizal fungi and climate regulation. It states that these fungi “help regulate Earth’s biogeochemical cycles” and that protecting their diversity can “help maintain critical ecosystem functions (for example, carbon sequestration) for realizing nature-based climate mitigation strategies.”
• It quantifies the role of these fungi in the carbon cycle, noting an “estimated 3.6 billion tons of carbon annually allocated through plants to mycorrhizal fungi.”
• The analysis of environmental predictors found that “Greater soil organic carbon was associated with higher EcM richness,” directly connecting fungal biodiversity to a key climate-related metric.

SDG 2: Zero Hunger

• The article connects mycorrhizal fungi to agriculture and food systems. It notes that “AM fungi form associations with around 80% of plant species and dominate in tropical forests, grasslands and croplands globally.”
• The fungi’s function is described as foraging “in the soil for phosphorus, nitrogen and trace elements,” which are essential for plant nutrition and, by extension, crop productivity. This relates to building resilient agricultural practices and improving soil quality.
• The study also notes that “Anthropogenic land-cover emerged as an important and positive predictor of AM fungal richness,” which has implications for managing agricultural landscapes to support beneficial microbial communities.

SDG 17: Partnerships for the Goals

• The entire study is an example of a global partnership for sustainable development. It was built by training “machine-learning algorithms on a global dataset of 25,000 geolocated soil samples comprising >2.8 billion fungal DNA sequences” compiled from multiple large-scale databases like “GlobalFungi, GlobalAMFungi and Global Soil Mycobiome consortium databases.”
• The article addresses the need for better data for sustainable development, aiming to solve the problem that “the global distribution of mycorrhizal fungal biodiversity is largely unknown.” It generates “high-resolution, global-scale maps” to fill these data gaps, particularly in under-sampled regions, which aligns with enhancing capacity and data availability.

2. Specific Targets Identified

Targets under SDG 15 (Life on Land)

1. Target 15.1: Ensure the conservation, restoration and sustainable use of terrestrial and inland freshwater ecosystems and their services.
   • The article’s focus on identifying “key reservoirs of highly diverse and endemic mycorrhizal communities” in various terrestrial ecosystems (forests, grasslands, etc.) directly supports the conservation of these areas.
2. Target 15.4: Ensure the conservation of mountain ecosystems, including their biodiversity.
   • The study specifically identifies mountain ecosystems as biodiversity hotspots, noting that “montane grasslands, tropical conifer forests and temperate broadleaf forests showed the highest AM fungal richness estimates” and that hotspots of endemic EcM fungi were predicted across “mountainous terrain in the Andes, Sierra Madre, Sierra Nevada and Cascade Mountain ranges.”
3. Target 15.5: Take urgent action to reduce the degradation of natural habitats and halt the loss of biodiversity.
   • The article’s primary conclusion that “mycorrhizal richness hotspots” are “poorly protected” is a direct call to action to halt the loss of this specific, crucial component of biodiversity.
4. Target 15.9: Integrate ecosystem and biodiversity values into national and local planning.
   • The research argues that “current conservation policy tends to rely on plant and animal diversity metrics” and that its findings on underground biodiversity should be used to “identify conservation priorities, set monitoring benchmarks and create specific restoration plans,” thereby integrating new biodiversity values into planning.

Targets under SDG 13 (Climate Action)

1. Target 13.2: Integrate climate change measures into national policies, strategies and planning.
   • By demonstrating the link between fungal diversity, ecosystem function, and carbon sequestration, the article provides a scientific basis for including the protection of soil biodiversity as a “nature-based climate mitigation strategy” in national plans.

Targets under SDG 2 (Zero Hunger)

1. Target 2.4: Ensure sustainable food production systems and implement resilient agricultural practices that…help maintain ecosystems…and progressively improve land and soil quality.
   • The article’s finding that AM fungi are dominant in “croplands globally” and are crucial for plant nutrient uptake implies that their conservation is integral to maintaining soil quality and ecosystem health within agricultural systems.

Targets under SDG 17 (Partnerships for the Goals)

1. Target 17.16: Enhance the global partnership for sustainable development…that mobilize and share knowledge, expertise, technology.
   • The study itself is a product of such a partnership, leveraging multiple global databases and a consortium of researchers to “share knowledge” and create a new global resource.
2. Target 17.18: Enhance capacity-building support…to increase significantly the availability of high-quality, timely and reliable data.
   • The article directly addresses “geographical biases” and “large data gaps” in soil biodiversity data and produces “high-resolution (1 km²)” maps to increase the availability of reliable data for conservation planning.

3. Indicators Mentioned or Implied

Indicators for SDG 15 (Life on Land)

1. Implied Indicator: Proportion of terrestrial area consisting of mycorrhizal fungal hotspots.
   • The article defines and maps these hotspots, identifying them as “pixels in the upper 95th percentile of predicted richness and rarity values globally.”
2. Implied Indicator: Coverage by protected areas of important sites for mycorrhizal biodiversity.
   • This is a central metric calculated in the article: “Globally, we predicted that only 9.5% of mycorrhizal richness hotspots occur in protected habitats.” This directly measures progress (or lack thereof) in protecting this form of biodiversity.
3. Implied Indicator: Mycorrhizal fungal richness and rarity-weighted richness.
   • The study develops these metrics (“AM and EcM fungal richness,” “rarity-weighted richness”) as key indicators of biodiversity health, which can be monitored over time.

Indicators for SDG 13 (Climate Action)

1. Implied Indicator: Soil organic carbon stocks.
   • The article uses soil organic carbon as a key environmental predictor and finds a strong link to fungal diversity, stating, “Greater soil organic carbon was associated with higher EcM richness.” This can be used as a proxy for the health of these carbon-sequestering ecosystems.
2. Implied Indicator: Carbon flux to mycorrhizal networks.
   • The article cites a specific value: “an estimated 3.6 billion tons of carbon annually allocated through plants to mycorrhizal fungi,” which serves as an indicator of their role in the global carbon cycle.

Indicators for SDG 2 (Zero Hunger)

1. Implied Indicator: Mycorrhizal fungal diversity in croplands.
   • Given that AM fungi “dominate in… croplands globally” and are linked to nutrient cycling, measuring their diversity in agricultural soils serves as an indicator of soil health and the sustainability of the agricultural ecosystem.

Indicators for SDG 17 (Partnerships for the Goals)

1. Implied Indicator: Availability of high-resolution, geolocated soil biodiversity data.
   • The article’s main output is the creation of “high-resolution, global-scale maps” of fungal diversity, directly contributing to this indicator by filling previously existing “data gaps.”

4. Summary Table of SDGs, Targets, and Indicators

Source: nature.com