At each sample site, Mario Muscarella, a collaborator and microbiologist at the University of Alaska, Fairbanks, marked the precise GPS coordinates, identified plant species at the surface, and jammed a probe into the earth to measure temperature and moisture. A lab would later analyze each site’s soil nutrients and extract DNA sequences from the samples to search for undiscovered fungal species.
The day carried us 50 more miles south through the North Slope to the Brooks Range. We drove past muskoxen, icy ponds, and fragrant hills traversed by Alaska’s high-pressure crude oil pipeline. At the end of day three, the team reached its 39th site, a sloped meadow overlooking the Kuparuk River — leaving the group 21 sites shy of its target with one day remaining.
The final day began with a stinging cold you’d expect from the tundra: 30 degrees Fahrenheit beneath thick fog. Yet it was June, and summer was well underway. We trudged through calf-deep snowmelt to a drier spot for the team to sample. Heaps of last summer’s grassy sedge lay withered around us. “It’s odorless,” Muscarella said, “but I’m sure that we’re breathing in a ton of methane right now.”
Long-dead plants, animals, and fungi were thawing after a cold winter, making their carbon accessible to microbial decomposers that digest complex organic gunk and belch simpler vapors: carbon dioxide, methane, and nitrous oxide, greenhouse gases all. As climate change tightens its grip over the Arctic, deeper layers of permafrost are activating in this way. Microbes no longer limit their feast to last year’s harvest: They can also liberate carbon that has spent thousands of years in frozen isolation.
Microbial fungi are key to understanding where that carbon is going. After decades of snubbing fungi as parasites or passive tubes, the escalating tally of their functions has led researchers to consider mycorrhizae a missing link in climate studies. In 2023, Van Nuland and Kiers helped estimate how much carbon is stored by fungi annually: 3.93 billion tons by arbuscular and 9.07 billion tons by ectomycorrhizal — a combined value that represents 36% of all carbon dioxide emitted across the planet every year.