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Monday, April 15, 2024

Carbon-Rich Peat Is Disappearing. But Is It Also Growing?

Thank peat for that scotchy flavor of Scotch whisky: The muck forms in Scotland’s bogs, when layer after layer of dead vegetation resists decay and compresses into fuel, which is burned during scotch distillation. But you can also thank peat for helping keep our planet relatively cool, as all that muck—which is particularly common across the Arctic—traps a tremendous amount of carbon that would otherwise heat the atmosphere. 

That peat is in serious trouble, and not because the world is drinking too much Scotch. As the Arctic warms, peat is drying out and igniting thanks to lightning strikes. These become some of the strangest wildfires on Earth, because they can smolder through the ground, moving slowly across the landscape until they pop up somewhere else—earning them the nickname “zombie fires.” Peat fires will even “overwinter,” burning under the snow and igniting new fires aboveground in the spring. These blazes can burn for months and release astonishing amounts of carbon into the atmosphere.

At the same time, the Arctic is greening, which might sound great, but it’s actually a slow-motion nightmare for the region’s ability to keep carbon sequestered. Like peat, permafrost—a combination of earth and ice—is a carbon sink. Yet the Arctic is warming up to four times as fast as the rest of the planet, making permafrost thaw so rapidly that it’s gouging holes across the landscape, releasing carbon. A greener landscape accelerates that thaw, because as shrubs become a more dominant form of vegetation, they trap more snow against the ground. This prevents the winter chill from reaching permafrost, meaning it thaws more readily.

Scientists, though, just discovered that there might be a small ray of hope as the Arctic greens. All of that plant growth may be building new peat, potentially offsetting at least some of the losses of carbon from peat fires and permafrost thaw. Working in the Svalbard archipelago in Norway, researchers took sediment cores, which you can see in the image below. The grayer, darker bits are mineral soils, but the greener, browner bits are layers of organic material, mostly moss. “The layers are still so young, so it's not fully mature peat yet, but perhaps it will become peat eventually,” says University of Helsinki paleoecologist Minna Väliranta, lead author of a paper describing the findings, which published in the journal Scientific Reports in March. “That's why we call it ‘proto-peat,’ because it's not peat yet, in a kind of proper sense.” 

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That’s because peat takes a very long time to form. First and foremost, peat needs to stay wet, which preserves the plant matter and stops it from rotting away. As new vegetation grows and then dies on top of this material, it also resists decay. Layer after layer forms over centuries or even thousands of years. (Peat also regularly forms in tropical regions, which are nice and wet.)

All of this creates a contradiction that scientists are only beginning to investigate: As the Arctic warms, more peat dries out and ignites, but more vegetation grows, which could eventually form new peat. “People think that there are no new peatlands initiating at the moment, but our data is—very tentatively, at least—showing that this is not the case,” says Väliranta.

The key variable, of course, is water: Will Svalbard and the rest of the Arctic stay wet enough, for long enough, to allow peat to develop? Peat is extraordinarily sensitive in that it can take centuries to form, yet it can vanish in an instant if it catches fire. “If these climate conditions and extreme weather conditions lead to surface drying, then they are prone to fires,” says Väliranta. “And then, of course, if the peatland burns, then all that carbon returns to the atmosphere.”

A more surprising variable is wildlife. In Svalbard, flocks of birds and herds of reindeer roam around, fertilizing the vegetation with their droppings, which encourages the growth of plants. As the Arctic continues to green, will more animal species also wander north, providing a critical source of fertilizer? Or, if reindeer populations grow big enough, will they eat so much vegetation that they actually discourage the formation of peat? Väliranta and other scientists can’t yet say.

They’re also not sure how much any new peatlands might offset those lost to wildfires. “Peat has the capacity to lock up carbon for a long time,” writes University of Zurich ecologist Jakob Assmann in an email to WIRED. (He studies Arctic greening but wasn’t involved in this new research.) “New peat formation in the Arctic could therefore potentially lead to long-term removal of carbon from the atmosphere. To my knowledge, it is currently very uncertain how much carbon could be removed from the atmosphere in this way and whether it would provide negative feedback to global warming.”

After all, there are only a small number of Arctic ecosystems that appear to be accumulating organic matter, compared to the widespread destruction of established peatlands. And proto-peat still has a long way to go before it’s full-blown peat—and only if it can stay wet. “Peatlands are being disturbed and destroyed globally at an unprecedented rate, where intact peatlands normally acting as a carbon sink become a carbon source,” says ecologist Scott Davidson, who studies peatlands at the University of Plymouth but wasn’t involved in the new research. “However, it is very interesting to see these processes occurring at these high Arctic systems, and it will be interesting to follow their trajectory under current climatic changes.”

Which is all to say: Betting on new peat to sequester the extra carbon that humanity is pumping into the atmosphere is a bad move, as there’s no guarantee the balance between recent growth and ongoing loss will tip in our favor. If we don’t massively crash emissions, no amount of natural carbon removal will save us from ourselves.

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