Every time you eat a blueberry, the microbiome in your gut gets to work. Bacterial enzymes attack the fruit’s organic compounds: a bubbling, gurgling digestive process that, often to our embarrassment, can cause us to pass gas. This may not seem like a big deal to humans, but new research shows that the microbial activity in icy Arctic soil may not be so different. On a global scale, this could mean that the planet is blowing up more dangerously greenhouse gases.
Permafrost, the frozen earth covering approx a quarter of the Northern Hemispherecaptures an enormous amount of planet-warming carbon — 2.5 times the amount currently in the atmosphere. But as the soil thaws, the microbial community in the soil wakes up and starts eating away at the trapped organic matter, releasing all that buried carbon into the atmosphere as greenhouse gases, which in turn trap even more heat around the planet. In a self-sustaining feedback loop, the warmer it gets, the more active soil microbes become. And new research suggests that scientists may not have realized how much of that carbon-sinking permafrost is at risk: Twice the estimated amount of carbon could be on offer for hungry microbes to decompose, which could lead to increased emissions.
“We were surprised that some of the exact pathways that exist in the human gut were shared by completely different organisms,” said Kelly Wrighton, a microbiology professor at Colorado State University who leads the lab. the study room, which was published last month in the journal Nature Microbiology. While she said this could mean much more future permafrost emissions than climate models have previously accounted for, more research is needed to determine exactly how much.
There is so much left to figure out, in fact, that many climate models failure to account for the thawing permafrost at all. Recent advances in technology, such as tracking methane with satelliteshelp us get a better idea of what is already seeping out of the ground and how the thawing landscape is changing. But what about the small organic forces that churn up all that carbon in the first place?
While half of all Earth’s carbon is stored in permafrost, not all of it is available for microbes to eat away and break down as carbon dioxide and methane. Based on a decades old theorysoil scientists used to think that polyphenols—a class of more than 8,000 organic compounds abundant in many plants—were not usable by microbes in permafrost conditions, which would prevent some carbon from escaping when the soil thawed.
This assumption has even led some researchers to suggest that limiting permafrost emissions may be possible by seeding the soil with polyphenol-rich matter. But polyphenols are also abundant in berries, nuts and many other types of food that people eat, and according to human health researchthe microbes in our stomachs handle them well.
Bridget McGivern, a microbiologist at Colorado State University and lead author of the study, says it was a contradiction between different scientific fields that have left researchers scratching their heads. “We thought: How can these two things be true in these different ecosystems? We know that most of the time, microorganisms follow the same rules across systems.”
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Recent advances finally allowed scientists to begin peering into the complex, diverse world of soil genetics and answering these questions. McGivern and her colleagues began by a open source gene tagging tool, which can compare genetic sequences that microbes express when feasting on polyphenols in different environments, including human digestive systems. Then the researchers used it to look closely at permafrost soil and found genetic evidence that microbes also break down the polyphenols there.
Before the study was published, McGivern says about 25 percent of all carbon trapped in the permafrost is thought to be available to microbes and factored into climate models. Now that polyphenols are on the microbial menu, that number has doubled—meaning twice as much carbon can be accessible to the microbes to decompose and convert into greenhouse gases.
There are still many gaps to fill, and estimating the permafrost’s future emissions requires more research from different fields. “But what we can say is that there’s this big carbon pool that we’ve been ignoring that we really need to pay attention to,” McGivern said.
Tyler Jones, a climate researcher at the University of Colorado, Boulder, agrees. “We’re a little behind,” he said. Decades ago, researchers thought that permafrost can stay frozen and does not pose an immediate climate threat. Fast forward to today, he said, and a rapidly changing Arctic has been found to be warming two to three times faster than the rest of the planet, which has caused a flood of urgent research. “There are currently so many missing puzzle pieces. We can’t even see what the full puzzle looks like.”
Other natural processes complicate the picture even further. Called in a process vegetation, plant life creeps further north and colonizes the earth that reveals retreating ice. Jones says all that extra plant life will soak up carbon, helping turn the Arctic into a carbon sink again. But research wise shrubs can trap snow before it can begin to cool the earth. McGivern points out that this may also mean more polyphenol-laden soil for the microbes to break down.
“The impacts are already unfolding,” said Jan Nitzbon, a permafrost researcher at the Alfred Wegener Institute. The ice is already reacting each fractional degree of warming – gradual thaw in some areas and collapse in bursts in others, threaten the ecosystem and people who live in it.
“Mitigation of carbon emissions, keeping global warming temperatures as low as possible — that’s kind of the only viable way to protect as much permafrost as possible,” Nitzbon said
