Is fungi the most underused resource in the fight against climate change?

Picture a group of “climate change warriors”, massing together in a battle to save the planet. Did you imagine a line of mushrooms? Well, maybe you should have, according to scientists at Boston University in the United States.

Fungi play a critical role in helping forests absorb carbon and combat the potential impacts of climate change, two Boston researchers say. Known as the “fifth kingdom of life on Earth”, there are millions of species of fungi and they are present everywhere: in water, in the air, in the soil, and on trees.

Most people know that mushrooms grow in the damp and shady areas of forest floors. But a species called mycorrhizal fungi can grow underground among the roots of trees. A particular variant known as ectomycorrhizal fungi helps trees and forests absorb CO2 more quickly, the scientists say.

This fungi can also slow down the speed at which carbon returns from forest soils into the atmosphere, helping forests to keep carbon locked up in trees and soils for longer.

However, fungal networks are under threat because of agricultural expansion, the use of chemical fertilizers and pesticides, deforestation and urbanisation. Fungal networks can’t survive without their plant partners, and any damage can take decades to repair.

Forests are disappearing at an alarming rate, with around 12 million hectares destroyed each year, according to the United Nations (UN). That’s roughly the size of 12 million rugby pitches.

Reducing this loss and promoting forest regrowth could lower net global emissions by up to 30%, the UN says, and one of the key agreements at the recent COP26 Summit in Glasgow was to end deforestation by 2030.

The giant underground network of fungi that forests support has become known as the “Wood Wide Web”, but very little is known about it and its role in combating climate change. This is why a project to map and preserve the planet’s underground fungal networks has been launched by the Society for the Protection of Underground Networks (SPUN).

The organization says mycorrhizal fungi are one of the biggest untapped areas of climate science.

“Billions of tons of carbon dioxide flow from plants into these fungal networks each year. These carbon flows help make soils the second-largest carbon sink after oceans,” SPUN says. A carbon sink is defined as something that absorbs more carbon-containing compounds than it releases.

Experts known as “myconauts” – mycology is the study of fungi – are collecting thousands of samples to make this global map of fungal networks. SPUN will then use machine learning to create a picture of these networks and their role as carbon sinks.

This mapping will be used to identify high-priority sites with the potential to store more carbon and survive extreme climate events.

“Understanding underground ecosystems better is a big opportunity for biodiversity and climate initiatives,” says SPUN governing board member Mark Tercek. “Fungal networks underpin life on Earth. If trees are the ‘lungs’ of the planet, fungal networks are the ‘circulatory systems.’ These networks are largely unexplored, yet remain one of the biggest untapped levers in science.”

The many benefits of fungi are now being applied to agriculture, according to the winner of the Association of British Science Writers Young Science Writer of the Year Award 2022, Zara Hussan.

Seeding soil with "friendly fungus" is seen as a promising technology for sustainable farming, she says in her award-winning essay. “Research conducted into planting one particular variety – Arbuscular mycorrhizal fungi, or AMF – in soil has shown how it can not only help enrich soil fertility but also reduce CO2 levels in the atmosphere.

“The benefits of so-called ‘biofertilizers’, like AMF, have resulted in the global biofertilizer market reaching a value of more than $2 billion.”

Hussan points out that reducing the use of chemical fertilizers on farmland would also benefit the fungi in forests.

The global map of fungal networks could provide us all with a more sustainable route into the future.