Northland peat bogs are carbon hogs, if they are intact
The U.S. Forest Service and The Nature Conservancy are researching how restored bogs help slow climate change.
SAX-ZIM BOG — Scientists have known for decades that peat bogs are carbon sinks, that their deep layers of organic matter built up over centuries can capture and store huge amounts of carbon dioxide.
But when you drain a bog, or mine it, or otherwise disturb it, bogs can go from carbon capturers to carbon emitters. All the carbon stored over millenia goes out into the atmosphere as carbon dioxide, increasing the buildup of greenhouse gasses causing global climate change.
It’s estimated that damaged and drained peatlands worldwide emit 2 billion tons of carbon dioxide annually, roughly 5% of all human-caused greenhouse gas emissions.
Now, scientists want to know what happens when you rebuild a peat bog, or re-wild it, restore it back close to its original boggy self? Will they go back to being carbon hogs? So far the answer appears to be a qualified yes. It all depends on water.
Researchers from The Nature Conservancy, the U.S. Forest Service, the University of Minnesota and Michigan Technological University are in the Sax-Zim Bog 40 miles northwest of Duluth measuring methane and CO2 emissions from special holes or wells they have drilled into the peat.
“We’re trying to develop a model for plant cover and water table depth and how those relate to carbon emissions,” said Kristen Blann, a freshwater ecologist for The Nature Conservancy in Minnesota. “The goal is to see if we can return the wetlands to CO2 sinks by restoring the original water depth and vegetation.”
Last year’s drought dried the peat bogs more than in any recent year. As a result, as organic matter dried out, CO2 emissions increased. This summer has been much wetter, and the water table in one bog the News Tribune visited is 24 inches higher than last, covering more plants and likely slowing emissions.
“If we can keep the bog wet, we can keep the carbon stored. That’s the big deal,” said Chris Lenahrt, a University of Minnesota professor who works with The Nature Conservancy.
Sphagnum peat bogs, and there are many varieties, cover only about 3% of the Earth’s surface area. But, acre-for-acre, peat is the best land cover on the planet to fight climate change, holding about 30% of all the stored carbon on Earth — twice as much as forests.
Minnesota has about 6 million acres of peatlands, covering nearly 10% of the state, the most of any state outside Alaska. A little more than 1 million acres of Minnesota’s peat has been drained, disturbed or degraded. Usually, that disturbance came by way of ditches that attempted to drain the very wet land so it could be used for farming or other purposes. Most of those were dug a century or more ago.
A few were attempted as recently as the 1960s, when millionaire chop suey magnate Jeno Paulucci tried farming the land to grow vegetables for his line of Chun King canned foods.
Almost all the bog-draining efforts failed. But they did scar the bogs enough so they stopped functioning as carbon sinks and became carbon emitters.
Bogs also are often methane emitters, and methane is another potent greenhouse gas. But if the bogs have a layer of living sphagnum moss growing on top and undisturbed, the moss acts as a blanket to hold the methane in. Healthy, functioning bogs offer a double dose of climate protection.
In Minnesota, on the southern edge of most peat bogs in the northern hemisphere, climate change already is impacting peat bogs. When temperatures rise, more evaporation occurs and water levels drop, the peat is dried and is exposed to oxygen. This starts the decomposition process that had been on hold underwater, converting carbon to CO2 and triggering its release. Climate change is having the same impacts as human ditching did a century ago.
“We need to know how wet the bog needs to be, figure out how to manage water levels to keep the carbon in the bog,” Blann said.
Researchers are looking both at former bogs that, thanks to beaver or sedimentation and other forces, are returning to their original water levels as well as bogs that are getting help from humans.
Near the Sax-Zim Bog area, there are two areas of disturbed, drained peat bogs that are being restored as part of wetland mitigation regulations. As new highways, construction or mining disturb or destroy wetlands, the companies or government agencies are required to create new wetlands to offset the loss. These so-called wetland banks were created over the past decade, projects to stop the flow of water escaping the bogs and let a natural bog take hold again.
Collin Tucker, a scientist with the Forest Service’s Northern Research Station, said it remains unclear how much restoration is needed to turn disturbed bogs from emitters of carbon to carbon sinks. On Thursday, he carried a backpack full of devices into the bog that can measure CO2, methane and water vapor to see what’s coming out.
“Some of these (bogs) are coming back on their own. ... But we don’t know yet at what stage they become fully functional again” as carbon sinks, Tucker said. “It’s all about how much water is down there.”
Restoring peat bogs has the added benefit of creating more plant and animal habitat for a multitude of species, some of which only live in the low oxygen, acidic-water bogs. Drive by a bog at 65 mph and you might only notice black spruce, willow and tamarack trees. But stop and look closer and you’ll see dozens of species of plants, from cranberries and pitcher plants to leather leaf, Labrador tea and bog rosemary.
“They support an incredible biodiversity of insects and moths … and, in turn, the birds that follow,” said Clinton Dexter-Nienhaus, head naturalist for the Friends of the Sax-Zim Bog group who helped guide a recent research trip into the bog.
Not every former bog can be restored. But researchers for the United Nations estimate that restoring millions of acres of peatlands globally could prevent annual emissions of nearly 400 million tons of carbon dioxide equivalents, both CO2 and methane, being released into the atmosphere.
That’s like taking 84 million gasoline-burning cars off the road.
“For us, it’s tiring to make good land management decisions,” Blann said. “If restoring degraded peat bogs can help reduce climate change, and become a natural climate solution instead of part of the problem, then that’s one of the tools we have to make an impact.”
How does peat form?
Minnesota's peatlands began to form 6,000 years ago when the climate cooled and precipitation increased significantly. Peat formation requires low-oxygen conditions that prevent normal decomposition of plant debris over many centuries. This occurs in areas of poor drainage where precipitation exceeds evaporation. The water table lies at or near the surface in these areas, saturating dead plant material. As a result, organic materials accumulate year-after-year, decade after decade, forming the partially decomposed mass known as peat.
Source: Minnesota Department of Natural Resources