Within weeks of a wildfire, an orange crust coats deadwood and the charred forest floor, creating an otherworldly landscape that still seems to be smoking.
But instead of continued destruction, it’s a signal of rebirth: tiny fungi are colonizing the wreckage.
“They shoot out spores, so many that it actually looks like smoke,” said Joey Tanney, a Canadian Forest Service mycologist and research scientist.
These peachy-orange fungi are pyronema, a type of pyrophilous — Greek for fire-loving — fungi that act as nature’s first responders to a wildfire. And the study of how these organisms help with fire recovery has grown as climate change boosts the size, intensity and frequency of wildfires.
Believed to be in a dormant state, fire-loving fungal spores remain latent until a wildfire, says Monika Fischer, a mycologist at the University of British Columbia (UBC) studying the role of fungi in a post-fire environment. Historically, lightning strikes started the majority of wildfires, and the organisms that survived them — like pyrophilous fungi — are those that could adapt.
The past three years have seen record-breaking wildfire seasons, each surpassing the historical annual average burn size of 2.7 million hectares, according to the Senate report released this month. In 2023, the most devastating year on record, 14.7 million hectares were destroyed by fire.
“We’re having all these unprecedented fire seasons. It makes understanding the post-fire environment — that includes the soils, fungi, all these different organisms — much more important,” Tanney said. “What’s the baseline? What can we expect after a ‘normal’ fire versus some of these more extreme ones?”
Soil insulates these organisms from the extreme end of the heat, which can reach up to 1,000 C at the surface.
At just three centimetres below, however, Fischer recorded temperatures of 70 C during a slash pile burn, a type of controlled fire that burns forest debris to lower the risk of wildfire, which was started in a clearcut clearing in California for her research.
“They’re just waiting for the heat to trigger that reaction,” Fischer said of pyrophilous fungi, noting that in the soil samples taken just hours after that fire, she could measure a marked increase in fungal numbers.
Pyrophilous fungi consume the ash, carbon and other toxic byproducts of a forest fire that have changed the chemical makeup of the upper soil layers. By devouring these harmful elements, including the significant amount of carcinogenic polycyclic aromatic hydrocarbons created during a wildfire, they can convert them into spores and “fruiting bodies,” which, in turn, become fuel for the secondary responders: insects, mites and bacteria, Tanney said.
“They’re basically starting the food web,” he said.
Erosion can also become a huge risk following a fire, because the plants and roots that stabilize the soil have burned away. And the soil surface becomes coated in a waxy layer that repels water, said Thea Whitman, a mycologist at the Life Sciences Institute at UBC, caused, in part, by the melting wax from evergreen needles and other trees.
“Now you’ve got sheets of water moving over the landscape, [which] if you’re in a hilly area, can create severe post-fire landslides,” she said.
Fungi have long, threadlike filaments known as hyphae — the main structural cells in the organism — and these can help stabilize the soil and minimize landslide risk after a fire.
“Microbes play a really important role in creating soil structure, binding soil particles together,” Whitman said. “They also probably play a role in decomposing that sort of post-fire waxy deposit on the surface.”
Whitman’s research has shown how fungi and plant communities rebound. Soil samples taken from 40 different sites at one year and then at five years after a 2014 fire in the northern boreal forest in Alberta and the Northwest Territories found the fungi and plants “were changing in step” with one another — and that those connections only increased over time.
“So that is kind of indicating that the recovery of the fungal communities is tied to the recovery of the plant community post-fire,” she said.
Other types of fungi are already used in antibiotics, statins, immunosuppressants and in industrial chemical applications. And since fire-loving fungi quickly break down charcoal and other harmful pollutants in nature, Fischer says it’s possible they could do the same in an industrial setting.
Whether these fungi could be manipulated to speed up forest recovery has not yet been tested. But Fischer says there’s some data that suggests small, prescribed burns “can almost act like a vaccine” and boost how pyrophilous fungi in the environment reacts to a wildfire.
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A small fire can cause each existing fungi to release many dormant spores, creating a much larger number that could react to the next significant fire, she says, noting these spores can survive for about 100 years.
“It sort of prepares the ecosystem for responding better in the future,” she said.
