Fighting wildfires with fungi

In our climate-changed world, forest fires are becoming bigger and more frequent. But the methods used to prevent them cause problems of their own. 

Thankfully, as it so often does, the humble mushroom might offer a solution.

In the first half of the 20th century, authorities in the US aimed for quick suppression of all wildfires, and successfully used new technology like aeroplanes and fire suppression chemicals to put out big blazes. But that is not quite the good news it sounds like.

Small fires are nature’s way of thinning out the trees. And once forests grow into a thick, branch-packed mass, they become an uncontrollable blaze waiting to happen.

Research has concluded that forest fires in the US during the period 1985-2020 have been more severe, and spread further, than the fires that burned 200 years ago. 

In an effort to reduce the risk, the US Department of Agriculture has set out a plan to reduce what they describe as ‘hazardous fuels’ across 50 million acres of forest land across the country. The idea is to use controlled burns, or to thin out the trees – cutting a pine down here and a fir down there, and stripping their branches.

A challenge of thinning, however, is that any piles of trunks and branches dotted around the forest are, themselves, kindling. Currently, there are around 140,000 piles of wood across the forests of northern Colorado alone.

The magic of mushrooms

Zach Hedstrom grew up in the foothills of the Rocky Mountains in Boulder, an area surrounded by dense green forest. He spent his spare time among the trees, and as he grew older, he noticed the growing woodpiles. 

He also started learning about the mushrooms that inhabited his local forests and joined his local mycology group. "There were a lot of older members in the organisation that were excited to see somebody young, participating and getting really excited," he told FairPlanet. 

A few years later, that excitement would inspire Hedstrom to come up with a solution that no one else had: letting fungi fight the fires.

As any homeowner who has experienced a bad case of dry rot will attest, certain fungi has the power to break down wood. Decay fungi grow through wood’s vascular tissues, and destroy the cell walls. The wood crumbles, eventually transforming back into the soil from which it grew.

Using his knowledge of fungi and professional identification literature, Hedstrom has found over 50 species of fungi that will get to work on foresters’ wood piles. They can make wood chips disappear into the forest floor within two years, he said, instead of the 20-50 years that would otherwise be typical in the region’s arid climate. 

To test each species' effectiveness, he applies its mycelium to wood and observes how quickly it decomposes - first in the laboratory and then through small-scale test plots against a control. 

"What our organisation is doing is playing a matchmaking role between the native fungi in our region and the wood species that are being removed," he explained. 

The idea to use fungi in this way came to Hedstrom in 2021, soon after he had launched his business, Boulder Mushroom, selling culinary and medicinal mushrooms to the local community.

"It was an incredibly humble start, I started the business out of the cabin that I'm sitting in now," he said, gesturing to the wood-walled room he’s speaking from. 

A grant from Boulder County Sustainability Office funded Hedstrom’s initial research, which is currently unpublished, but found that wood inoculated with mycelium holds more moisture and decomposes faster than non-inoculated wood. Since then, he has developed various ways to get the right fungi to the right wood, typically using a fungi-infused liquid that can be sprayed on large areas.

His fire-fighting fungi has now reached land across four counties in Colorado, and he hopes to bring it to other US states in the coming years. 

It is an approach that seems to offer benefits over the alternatives. The wood could be hauled away in huge, costly, gas-guzzling vehicles. Or it could be burned, releasing carbon into the atmosphere. Hedstrom explained that burning has become "really operationally challenging. Controlled burns are becoming harder and harder to do, simply because our climate is changing in such a way that there are less safe, operable, burn windows."

Benefiting the forest

Dr Lynne Boddy is Professor of Fungal Ecology at Cardiff University in the UK, and specialises in wood decay processes. She highlights the benefits of natural decomposition - such as that enabled by fungi - for the overall health of the forest.

"It is very important that natural decomposition occurs in ecosystems," she explained, "because this will accumulate good organic matter in the soil, and the soil will have good water holding properties." She added that this is preferable to burning, which would result in "the carbon dioxide and water just going immediately into the air."

Hedstrom hasn’t yet come up against any downsides to the fungal approach to fighting fires. "It's very low-risk," he said, "because we're using all native species. And we're putting them into an environment where they really are there for one purpose, which is to decompose wood that is already dead. One of the things that really excites me about this work is that it is very, very benign."

The species he currently works with are native throughout the western US, but working further afield would require different, local native species to be identified.

Maintaining balance

This commitment to using locally sourced native species will be crucial, Dr Boddy stressed. "You just can't go willy-nilly and inoculate things. People do, and it's very, very dangerous from an ecology perspective and ecosystem perspective. Because if you inoculate non-native species or genotypes they may be invasive."

Hedstrom is now looking to scale his work in Boulder and beyond. Fire mitigation efforts need to happen across millions of acres, not just pile by pile. He has a laboratory near his lodge in Boulder, which is home to his growing strain bank of fungi species.

His time is spent researching, experimenting and developing the technology needed to get the right fungi to the right wood.

Dr Boddy pointed out that rigorous testing will be essential, and should not be overlooked in the interests of speed and scale. "It’s important to be really, really cautious. It is hard to do trials on a big scale, because it's a huge amount of work. But you have to replicate treatments on the same site, and on different sites." Not least, she added, because ecosystems operate in balance.

"I don't know what effect saturating an area with a single species would have," Dr Boddy said. "That's something that needs to be looked at very carefully. If you increase the population size of a single strain, you don't know how antagonistic it is to other fungi. One has to be very careful of disrupting the balance of natural communities."

While science could (and should) slow things down, foresters he has worked with so far have been enthusiastic about his idea, he said.

"Foresters tend to be more conservative, but most of the foresters that we've talked to have become incredibly excited about the idea. I think there’s a lot of desire for assistance. This problem [of forest fires] is not going to get any easier," Hedstrom added.

"Professionals in that space are really hungry for anything that they can do. We’re hoping that this can be one additional solution."

Image by Sneha Chandrashekar.