Digging into Minnesota's peat, an underappreciated climate superhero
Updated: Oct. 11, 1:08 p.m. | Posted: Oct. 10, 4 a.m.
Colin Tucker slid on rubber waders, hoisted a 50 pound pack stuffed with carbon dioxide and methane analyzers and other heavy scientific monitoring equipment, and prepared to trudge through a mucky bog in northern Minnesota. It is home to a key ingredient in the world’s efforts to mitigate the impacts of climate change.
"Is everybody ready?” the ecologist with the U.S. Forest Service called out. Leading a team of researchers from the Nature Conservancy and the University of Minnesota, he hopped over a ditch filled with water in the Sax-Zim Bog. It is a vast area of more than 300 square miles of swampy forest about an hour northwest of Duluth.
Walking across the bog is like stepping on a giant, soggy carpet of sphagnum moss in vibrant hues of pink and green. Tucker calls the moss the ecosystem engineer of the peatlands. Cranberry bushes pop up out of the wet earth. Stunted tamarack and black spruce dot the landscape.
“This is the sound of the peatland, that sucking-off-my-boot sound,” he said, as he squishes over a layer of peat about six feet thick that's slowly built up over thousands of years.
When the moss dies, it's trapped in ground so wet and acidic that it can't decompose. Instead, it gradually builds up, layer upon layer, over centuries.
In drier conditions, when plants or trees die, oxygen helps break them down. That releases their stored carbon back into the atmosphere. But that doesn't happen in peat bogs. Instead, the carbon stays locked up in the peat.
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That makes peat an unsung “climate change superhero,” said Chris Lenhart, a University of Minnesota professor and researcher for The Nature Conservancy.
Peatlands cover only about three percent of the earth’s surface (nearly 10 percent of Minnesota’s acreage), but they store about 30 percent of the earth’s soil carbon.
“That means peatlands store comparable amounts of carbon to the world's forests,” Tucker said, even though they occupy only about one tenth as much land.
And while there has been a lot of focus on planting trees to suck carbon dioxide out of the atmosphere, “less is known about how we can manage global peatlands to enhance carbon storage, or at least to reduce carbon loss from peatlands,” he said.
To that end, Tucker and other scientists in northern Minnesota are working to figure out how best to restore drained peatlands to maximize the amount of carbon they can sequester.
Meanwhile, another nearby experiment is peering into a frightening climate future, and asking what happens to these peatlands as the world warms.
Could they turn from carbon sinks into a powerful carbon emitter, into “a runaway source of carbon emissions into the atmosphere?” asked Kristen Blann, a freshwater ecologist with the Nature Conservancy. “This is a big concern.”
Drained Peatlands
A century ago, settlers in northern Minnesota didn't care that peat bogs are some of nature's most powerful carbon sinks. They saw them as big, mucky areas standing in the way of what they recognized as progress — fertile farms and productive forests.
So they dug an estimated 2,500 miles of ditches in northern Minnesota to drain them. Globally, about 15 percent of the world’s peatlands have been drained, according to the United Nations.
A recent U.S. Forest Service analysis estimated that in northern Minnesota alone, the peat destroyed by that ditching released 3.8 million metric tons of carbon into the atmosphere. That's equivalent to the CO2 released by about 3 million cars in one year.
The ambitious drainage effort largely failed. The land was mostly abandoned and returned to counties and the state. But the ditches mostly remain. According to Blann, an estimated 500,000 to a million acres of peatlands in Minnesota have been degraded by failed drainage attempts.
Now, Blann and others say restoring those peatlands, by filling in or plugging the ditches, could be one of the most cost effective strategies for fighting climate change.
In addition to transitioning away from fossil fuels, they argue so-called natural climate solutions, including reforestation and restoring peatlands, are needed.
"You know, it's all hands on deck,” she said. “So we need to use all of our landscapes, in addition to reducing emissions in order to kind of reverse the trajectory of accumulating greenhouse gases."
Research has shown that removing or plugging drainage ditches and re-wetting wetlands greatly reduces the release of carbon dioxide by slowing down the breakdown of organic matter, explained the University of Minnesota’s Lenhart.
But it’s more complicated than just flooding the peatlands, he said. Because peatlands can also emit methane, a more short-lived but much more powerful greenhouse gas than carbon dioxide.
So in the Sax-Zim Bog, researchers are measuring how much carbon dioxide and methane the peat is breathing in, or breathing out, at ten different sites across the bog—some close to the drainage ditch, some far away.
Other research has found that if restored wetlands are simply filled with lots of water, they often release high amounts of methane, Lenhart said. But if the moss is also restored on top of the peatland, it acts almost like a big air filter, slowing down the release of methane gas.
Tucker said the results of their work so far show a complicated picture, where methane emissions are higher than he expected in some areas, but lower in places where they expected higher releases of methane. “And so I think there's a lot of work to be done on that side of the story,” he said.
But “we are desperate to find natural climate solutions,” Tucker added. The goal is to help figure out where it makes the most sense to re-wet drained wetlands, “to most effectively suck up carbon dioxide without emitting methane. And then really focusing efforts on those locations.”
A warmer future
Sixty miles to the northwest, one of the largest ecosystem-level experiments on the planet is taking place in the middle of the woods in northern Minnesota. There, a team of scientists is measuring exactly what will happen to the world’s swampy peat bogs as the climate warms.
The experiment is called SPRUCE, short for Spruce and Peatland Responses Under Changing Environment.
Funded by the Department of Energy’s Oak Ridge National Laboratory, it looks like something ripped from an Isaac Asimov novel. In the Chippewa National Forest, about a half mile north of Grand Rapids, ten huge chambers are scattered in the woods, 36 feet across, 24 feet high, seeming like high-tech terrariums.
Each features different temperatures and levels of carbon dioxide — ranging from about four degrees Fahrenheit above current temperatures, to 14 degrees above — to simulate possible future levels of global warming.
A sign above the door of each enclosure reads “Welcome to a warmer future.”
“It's just a simple message, but it conveys a lot of information,” said Steve Sebestyen, a research hydrologist with the U.S. Forest Service
Inside, fans continuously blow warm air around the chamber. A camera takes several pictures a day of the patch of forest below, to record when the trees change color, when the shrubs flower.
To measure greenhouse gas emissions, sensors sit in small domes, like big clam shells. They close automatically every few minutes to take a reading. There are devices measuring how much water trees are taking up through their roots. There are rain and wind gauges.
If it can be measured, either above or below ground, it probably is.
“This experiment really is designed to look at the whole ecosystem, and how it responds to drivers of climate change,” Sebestyen said.
The peat at this site is nearly 30 feet deep in spots, built up over millennia since glaciers subsided thousands of years ago.
Metal supports for the enclosures in some places sink 90 feet into the ground. During construction, builders found a tree buried in the peat, perfectly intact. So the scientists carbon dated it.
"And it's somewhere between 4,000 and 5,000 years old. And it looks like it was just deposited yesterday into the peatland,” said Randy Kolka, a soil scientist with the U.S. Forest Service and one of the co-principal investigators on the project.
But in the experiment's artificially warm enclosures, the peat ecosystem is changing rapidly. The water table is dropping. Trees are dying. Shrubs are growing like crazy, especially blueberries. And the peat is emitting more carbon dioxide as well as methane, a potent greenhouse gas.
"In the case of these ecosystems, we have definitely flipped them from being carbon sinks to sources. And it's most visible, the warmer the temperatures get,” Kolka said.
Even at moderate warming, at two and a quarter degrees centigrade— about four degrees Fahrenheit— “we see the ecosystems are turning from sinks to sources," said Kolka. “And it just gets exacerbated as you get higher and higher in temperature."
Perhaps most startlingly, scientists have physically measured the loss of two inches of peat in the warmest enclosures.
"It takes maybe 500 to 1000 years to accumulate that two inches, whereas we've just blown it off in just five years of the experiment,” said Kolka.
Hundreds of scientists, students and technicians from around the world will continue to work on the experiment through 2025 when it's scheduled to end.
Kolka and Sebestyen say the information they're gathering is starting to be incorporated into global climate change models. Peatlands aren't integrated into those models yet, because they’re not well understood. They say that will give a more accurate picture of what's going to happen to our future climate.
“At a minimum [the experiment] has made hopefully the planet more aware how important these ecosystems are for our future climate,” said Kolka.
“And hopefully, places that have a lot of peatlands will start thinking about ‘how do we conserve peatlands? Or restore ones that have already been degraded, to regain that carbon sink?’”
Corrections (Oct. 11, 2022): An earlier version of this story misidentified a person in the primary photo and story. The caption and story have been updated.
Editor’s note: The story has been updated to reflect a more accurate mileage of ditches dug to drain peatlands in northern Minnesota.