As planet-warming carbon emissions rise, a major solution to climate change is growing beneath our feet.
A study published Monday in Current Biology found that fungi gobble up more than a third of the world’s annual fossil fuel emissions.
As such, fungi “represent a blind spot in carbon modeling, conservation, and restoration,” coauthor Katie Field, a professor of biology at the University of Sheffield, said in a statement.
“The numbers we’ve uncovered are jaw-dropping,” Field added.
Field’s team found that fungi pulled down 36 percent of global fossil fuel emissions — enough to cancel out the yearly carbon pollution from China, the world’s largest carbon emitter. China beats out its nearest polluting competitor, the United States, by a factor of two.
Fungi are the broad biological kingdom that produces mushrooms — the fruiting bodies of far larger organisms that sprawl beneath the surface.
While superficially plant-like because they move so slowly, fungi are far more similar to animals, with whom they share the need to find food and use chemicals to break it down — rather than fabricating nutrients from sunlight and carbon dioxide.
Some fungi weave around the questing root tips of plants, forming a symbiotic relationship that serves as an ancient foundation to life on land.
For nearly half a billion years, these “mycorrhizal fungi” — named for the combined Latin words for “fungus” and “root” — have provided plants with mineral nutrients like phosphorous in exchange for plant-manufactured sugars.
Since those plants are making that sugar out of carbon dioxide from the air, that means that the fungi are in effect a growing subterranean “carbon bank.”
Some are quite large: One famous giant fungus in Michigan’s Upper Peninsula sprawls across 37 hectares, or 91 acres.
Globally, the world’s plants pump an estimated 13 gigaton of carbon dioxide into underground fungi each year, the study found.
But despite their importance, these subsurface fungal networks are continually broken open by the many ways human society interacts with the subsurface world — through agriculture, mining and industry.
That interference is taking a steep toll. The U.N. warned last year that 90 percent of the earth’s topsoil — the thin fertile skin from which the world’s crops and forests grow — could be at risk by 2050.
While the food impacts of such a degradation are obvious, the climate impacts are severe too, the team found.
The great pool of carbon held in mushrooms is often “overlooked” in favor of more obvious conservation efforts like forest protection, said lead author Heidi Hawkins of the University of Cape Town.
Hawkins cautioned that there is much about the specifics that remain unclear.
Like forests — which release carbon dioxide as trees die and store it as they grow — the portrait of mushrooms as a one-way carbon vault is overly simplistic. Hawkins noted that we still don’t know how stable carbon stored in mushrooms is.
“We do know that it is a flux, with some being retained in mycorrhizal structures while the fungus lives, and even after it dies,” she said.
Some of those carbon molecules may break down further to be bound in solid form into minerals in the soil. Some may be bound back into the bodies of new plants.
And others are lost back into the atmosphere — because fungi, like animals, release carbon dioxide as a waste product of respiration.
But while the specifics of these relationships are still little understood, their broad strokes are clear, Field said.
“When we disrupt the ancient life support systems in the soil, we sabotage our efforts to limit global heating and undermine the ecosystems on which we depend,” she added.
While it’s not news that these networks are crucial to biodiversity, “now we have even more evidence that they are crucial to the health of our planet,” Field added.