Level 1 - Absolute Beginner

Under the ground, there are tiny threads made by fungi. Fungi are living things, like mushrooms. These threads connect the roots of plants together. Scientists call this a 'fungal network.'

Scientists have now made a map of these networks all around the world. They found that most plants use these networks. The networks help plants get food and water from the soil.

The networks are also very important for our planet. They store a lot of carbon dioxide gas inside the ground. Carbon dioxide is the gas that warms our planet, so storing it is very good.

fungi

a group of living things including mushrooms and mold that grow in soil or on plants

network

a system of connected things that work together

roots

the underground parts of a plant that absorb water and nutrients

soil

the top layer of the ground where plants grow

carbon dioxide

a gas in the air that plants absorb; too much of it warms the planet

map

a picture that shows where things are in the world

store

to keep something in a place for later use

thread

a long, thin strand of material, like a tiny fiber

Level 2 - Elementary

Scientists published a landmark study in the journal Science on June 15, 2026, revealing the first complete map of arbuscular mycorrhizal (AM) fungal networks across Earth's topsoils. These underground threads, which can be thinner than a human hair, connect the roots of about 70 percent of all plant species worldwide.

To create the map, researchers analyzed more than 16,000 soil samples collected from over 4,000 locations around the globe. They used machine-learning models to fill in the gaps between sampling sites. The total length of the fungal threads discovered is approximately 110 quadrillion kilometers, an almost unimaginable distance.

The study found that these fungal networks store around four billion tonnes of carbon dioxide each year by absorbing it from plant roots and locking it in the soil. However, scientists warned that the networks are most at risk in tropical regions, where farming and deforestation are destroying them fastest.

arbuscular mycorrhizal

a type of fungus that lives inside plant root cells and exchanges nutrients with the plant

topsoil

the upper layer of soil, roughly the first 30 centimeters, where most plant roots and organisms live

landmark study

an important piece of research that changes understanding of a subject

machine learning

a type of computer program that learns from large amounts of data to make predictions

quadrillion

the number 1,000,000,000,000,000, or one thousand trillion

tonne

a metric unit of mass equal to 1,000 kilograms

deforestation

the large-scale cutting down of forests, usually to use the land for farming

sampling

collecting small amounts from many locations to study the whole area

Level 3 - Intermediate

A global mapping effort led by Justin D. Stewart and colleagues from the Society for the Protection of Underground Networks (SPUN) has produced the first quantitative atlas of arbuscular mycorrhizal (AM) fungal hyphae in Earth's topsoils, published in Science on June 15, 2026 (DOI: 10.1126/science.adu4373). Analysing over 16,000 soil cores from more than 4,000 sites worldwide and using machine-learning extrapolation to cover unsampled regions, the team estimated a total hyphal length of approximately 110 quadrillion kilometers in the top 30 centimeters of soil.

AM fungi form obligate symbioses with roughly 70 percent of terrestrial plant species, threading filaments called hyphae through root cells to exchange mineral nutrients for photosynthetically derived carbon. The new map reveals that these networks collectively sequester approximately four billion tonnes of atmospheric CO2 per year, an ecosystem service equivalent to about 13 percent of global fossil-fuel emissions, by incorporating organic carbon into stable soil aggregates.

The map also identifies a troubling geographical pattern: hyphal density is highest in humid tropical forests, precisely the ecosystems experiencing the greatest rates of agricultural conversion and deforestation. The researchers developed an interactive tool called the Mycorrhizal Infrastructure Map to allow policymakers and conservationists to identify priority zones for soil protection and direct subsidies toward practices that preserve underground biodiversity alongside the more visible canopy.

hyphae

the microscopic thread-like filaments that make up the body of a fungus

obligate symbiosis

a relationship where two organisms are completely dependent on each other for survival

extrapolation

using known data from sampled areas to estimate values in unsampled areas

sequester

to capture and store a substance, especially carbon dioxide, preventing its release into the atmosphere

soil aggregate

a cluster of soil particles bound together by organic material, fungi, or minerals

photosynthetically derived

produced by plants using the energy from sunlight to convert CO2 into sugars

agricultural conversion

the process of changing natural land into farmland

canopy

the uppermost layer of a forest, formed by the crowns of the tallest trees

Level 4 - Advanced

The publication by Stewart et al. in Science (DOI: 10.1126/science.adu4373, June 15, 2026) of a global, high-resolution quantitative map of arbuscular mycorrhizal (AM) hyphal biomass represents a transformative advance in soil biogeography. By assimilating 16,000 soil cores from 4,000-plus globally distributed sites into a gradient-boosted ensemble model, the SPUN consortium produced gridded estimates of AM hyphal length at 1-kilometer resolution across all ice-free land surfaces, yielding a total infrastructure figure of 110 quadrillion kilometers, a value that dwarfs every human-built network by roughly twelve orders of magnitude.

The ecological significance of this infrastructure operates at two scales. At the plant level, AM hyphae penetrate host root cortical cells, forming arbuscules that mediate a bidirectional exchange of mineral phosphorus and micronutrients from fungal scavenging against hexose sugars translocated from photosynthate, an obligate mutualism that enabled the colonization of terrestrial environments by vascular plants some 450 million years ago. At the planetary level, the map's carbon accounting reveals that AM networks immobilize approximately four billion tonnes of atmospheric CO2 annually by incorporating glomalin-related soil protein and hyphal walls into macro-aggregate structures resistant to microbial mineralization, an ecosystem service that existing Earth-system models have systematically underestimated.

The map's most alarming finding is the inverse relationship between AM hyphal density and land conversion pressure: peak hyphal biomass is concentrated in humid tropical forests, the same landscapes subjected to the highest rates of agricultural frontier expansion. Stewart et al. calculate that maintaining current deforestation trajectories would eliminate roughly 30 percent of the AM hyphal infrastructure in carbon-critical biomes within thirty years, releasing a pulse of soil-stored carbon that would materially offset decarbonization gains from renewable energy deployment. The authors recommend integration of mycorrhizal health indices into national greenhouse-gas inventories and the designation of high-hyphal-density soils as protected carbon assets under IPCC reporting frameworks.

biogeography

the study of the distribution of species and ecosystems across geographic space and through time

gradient-boosted ensemble model

a machine-learning approach that combines many decision-tree models, each correcting the errors of the previous, to improve prediction accuracy

arbuscule

a tree-like structure formed by AM fungi inside plant root cells that facilitates nutrient exchange

glomalin

a glycoprotein produced by AM fungi that binds soil particles into stable aggregates and stores carbon

macro-aggregate

a large cluster of soil particles and organic material held together by fungal threads and organic glues