Fungi hold the planet’s ecosystems together. They decompose dead matter, feed plants, store massive amounts of carbon underground, and supply humanity with essential medicines, foods, and industrial tools. About 155,000 fungal species have been formally described, but scientists estimate millions more remain unnamed, meaning we’re only beginning to understand what this kingdom does.
Decomposition and Nutrient Cycling
Without fungi, dead plants would pile up indefinitely. Fungi possess an efficient extracellular enzyme system and vast networks of thread-like filaments called mycelium that allow them to break down complex organic materials, including cellulose and lignin, the tough structural compounds in wood and plant cell walls. No other group of organisms degrades lignin as effectively. By dismantling dead leaves, fallen trees, and crop residue, fungi release carbon, nitrogen, and phosphorus back into the soil where living plants can use them again.
This recycling role makes fungi the primary drivers of soil nutrient cycling. In grassland ecosystems, for example, fungal communities directly control the pace of carbon breakdown and nitrogen release. As ecosystems mature, the fungal community shifts its activity, ramping up carbon fixation and nitrogen cycling in ways that sustain plant growth over decades. Without this constant recycling, soils would become sterile within a few growing seasons.
Feeding Plants Through Underground Partnerships
More than 80% of terrestrial plant species form symbiotic relationships with mycorrhizal fungi. The fungi colonize plant roots and extend their mycelium far into the surrounding soil, effectively expanding a plant’s root system by orders of magnitude. In return for sugars from the plant, the fungi deliver water, phosphorus, and other minerals the roots alone can’t reach efficiently. This partnership also improves drought tolerance and root structure.
The relationship isn’t always perfectly balanced. When fungal demand for plant sugars outweighs the nutrients delivered, plants can experience a net cost rather than a benefit. But in most natural and agricultural settings, the trade is overwhelmingly positive. A large-scale field study found that treating maize crops with mycorrhizal fungi improved yields by up to 40% without any additional fertilizers or pesticides. That result points to a practical future where fungal partnerships replace some of the synthetic inputs modern agriculture relies on.
A Massive Underground Carbon Reservoir
Roughly 75% of terrestrial carbon is stored belowground, and mycorrhizal fungi sit at a critical entry point for carbon moving from the atmosphere into soil. A global analysis of nearly 200 datasets estimated that plants funnel about 13.12 gigatons of CO₂ equivalent per year into the underground mycelium of mycorrhizal fungi. That figure equals roughly 36% of current annual CO₂ emissions from fossil fuels.
This carbon doesn’t all stay locked away permanently, but fungi do stabilize a portion of it in forms that persist in soil for years to decades. Understanding and protecting these fungal networks could become a meaningful piece of climate strategy, particularly in forests and grasslands where the networks are densest.
Medicines That Changed Human Health
Some of the most important drugs in modern medicine came from fungi. Penicillin, discovered in a mold in 1928, launched the antibiotic era and remains in clinical use today. Cephalosporins, another major class of antibiotics, also originated from a fungal species. Beyond fighting infections, fungi gave us cholesterol-lowering statins. Lovastatin and mevastatin, both derived from mold species, work by blocking a key enzyme in cholesterol production. They became the foundation for one of the most widely prescribed drug classes in the world.
Fungi also produced several immunosuppressant drugs that made organ transplantation viable. Cyclosporin A, isolated from a soil fungus, prevents the immune system from rejecting transplanted organs by suppressing a specific type of immune cell. Another fungal compound became fingolimod, used to treat multiple sclerosis by modifying how immune cells move through the body. The range is remarkable: a single biological kingdom yielded antibiotics, cholesterol drugs, and transplant medicines.
Food Production and Fermentation
Yeasts are single-celled fungi, and one species in particular, Saccharomyces cerevisiae, is arguably the most economically important microorganism on Earth. It drives the fermentation of bread, wine, and beer by converting sugars into ethanol and carbon dioxide. In brewing, a related species called S. pastorianus handles lager production, while S. cerevisiae makes ales. Each brewery typically maintains its own selected yeast strains tailored to its specific recipes.
Beyond alcohol and bread, fungi are essential to chocolate production. During the early anaerobic phase of cocoa fermentation, yeasts consume the sugars in cocoa pulp and produce ethanol and carbon dioxide, a step that develops the precursor flavors of finished chocolate. Cheese, soy sauce, tempeh, and miso all depend on fungal fermentation as well. Non-Saccharomyces yeasts contribute aromatic compounds like esters, higher alcohols, and fatty acids that shape the flavor profiles of wines and specialty foods in ways the standard brewer’s yeast cannot.
The global mushroom market alone was valued at $65.6 billion in 2024, with food applications accounting for nearly 87% of that revenue. The market is projected to reach $156 billion by 2033, reflecting growing demand for mushrooms as both a protein source and a functional food.
Industrial Enzymes
Fungi produce enzymes that work efficiently at industrial scale, and several are now standard ingredients in products you use daily. Cellulases, lipases, and proteases derived from fungal species are key active components in laundry detergents, where they break down plant-based stains, fats, and protein residues on clothing. The same enzyme classes are used in textile manufacturing to soften fabrics, remove sizing agents, and finish garments. Fungal lipases are favored commercially because they’re cheap to extract, stable across a wide range of temperatures and pH levels, and work well in organic solvents.
Cleaning Up Pollution
Fungi can break down synthetic materials that persist in the environment for centuries. A growing body of research shows that fungal strains, predominantly from the Ascomycota group, can degrade polyethylene, polystyrene, polypropylene, polyvinyl chloride, and polyurethane within months. Species of Aspergillus, Penicillium, Fusarium, and Cladosporium have all demonstrated the ability to physically colonize and chemically dismantle plastic polymers. One well-studied species, Pestalotiopsis microspora, breaks down polyurethane in oxygen-free conditions, which opens possibilities for treating buried or submerged plastic waste.
This field, called mycoremediation, extends beyond plastics. Fungi have been tested against petroleum spills, heavy metals, and pesticide residues in contaminated soils. Their mycelial networks can penetrate substrates that bacteria can’t easily access, giving them a structural advantage in breaking down pollutants spread through soil or sediment.
Biodiversity We’re Still Discovering
Of the roughly 155,000 accepted fungal species, over 97% belong to just two major groups: the Ascomycota (about 99,000 species, including cup fungi, molds, yeasts, and lichens) and the Basidiomycota (about 53,000 species, including mushrooms, rusts, and smuts). Early estimates put the total number of fungal species on Earth at 1.5 million, but more recent molecular studies suggest the real number could be several million. That means the vast majority of fungal life has never been studied, named, or tested for useful properties. Every ecosystem sampled with modern DNA sequencing tools turns up new species, particularly in tropical soils, deep ocean sediments, and extreme environments like hot springs and glacial ice.