We can’t see them, but there are more microbes — tiny fungi, bacteria, worms and other living things — in a teaspoon of soil than there are people on Earth.
Hungry as you and me, those microbes gobble up bits of plant and animal material. And just like you and me, soil microbes release greenhouse gases after they eat.
Unless their bodies happen to be frozen. Microbes in permafrost (soil that has remained frozen for two or more consecutive years) can remain in suspended animation for thousands of years. Permafrost underlies the surface of one-quarter of the globe’s land and more than half of Alaska.
That frozen ground would seem to stall microbes — especially in winter — but scientists have been finding robust emissions of greenhouse gases from tundra and forested areas during spring, summer, winter and fall.
Grant Falvo reported high winter emissions of carbon dioxide and methane from Alaska permafrost sites he visited in 2024. Falvo is a postdoctoral scholar at Northern Arizona University who presented his results at the Fall Meeting of the American Geophysical Union in Washington, D.C. in December 2024.
Falvo targeted long-term monitoring sites in permafrost regions across the globe that have for years been places that have taken up more carbon from the air than they have emitted via soil microbes.
Nineteen of the stations exist in Alaska, Canada and northern Europe. Following Alaska’s second-warmest winter on record, Falvo visited Alaska sites in Healy and also near Delta Junction and Fairbanks in late summer 2024.
He found more carbon emissions from northern forests and tundra in winter than would happen by chance. That seems to indicate that soil microbes were active in wintertime when people might have assumed they were dormant.
“We’re in our offices in winter, and that’s when these microbes are releasing carbon,” said Ted Schuur, Falvo’s supervisor and a professor at Northern Arizona University.
Permafrost, Schuur said, has thawed so deeply in places that it doesn’t re-freeze in winter, allowing microbes to emit greenhouse gases even if cold air has frozen the ground above them.
At the same meeting Falvo and Schuur attended, other researchers declared that Arctic tundra is now a small net source of carbon dioxide when wildfire emissions are included in the equation. Not all scientists agree on this.
For a very long time, most researchers considered Arctic tundra a carbon sink, a place where more carbon is stored in frozen ground and new plants than is emitted.
Part of that possible change is the year-round work of many soil microbes that had been slumbering for thousands of years.
“Permafrost isn’t permanent,” Schuur said.
• Since the late 1970s, the University of Alaska Fairbanks’ Geophysical Institute has provided this column free in cooperation with the UAF research community. Ned Rozell ned.rozell@alaska.edu is a science writer for the Geophysical Institute.
Victor Leshyk of Northern Arizona University created this artwork of microbes — in this case bacteria — and their activity in different states of frozen and unfrozen ground. (Courtesy of Northern Arizona University)
