Study: Southeast’s peat bogs have carbon storage superpowers
Rewetting drained coastal evergreen shrub bogs in the Southeast that were once used for farming could make a small but significant contribution to reducing U.S. carbon dioxide emissions, according to a recent study.
The bogs, known as pocosins, can absorb and hold extraordinary amounts of CO2 because they contain antimicrobial compounds called phenolics that prevent the waterlogged peat from decaying rapidly, even during times of drought.
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“Southern pocosin peatlands punch far above their weight in terms of their capacity for carbon storage. Acre for acre, they can store significantly more carbon than forests or grasslands,” said Curtis J. Richardson, founding director of the Duke University Wetland Center, who led the research — the first to show how rewetting such bogs can change them from emitting carbon to storing it.
Richardson’s study estimated that about 250,000 of the 1.7 million acres of pocosin peatlands in the Southeast — from Virginia to Georgia — are no longer used as productive farmland and could be restored to functioning wetlands. Doing so would prevent the 4.3 million tons of CO2 locked up in those acres from oxidizing and escaping back into Earth’s atmosphere. That’s 2.4% of the total annual reductions in carbon emissions needed for the U.S. to be carbon neutral by 2050.
Some researchers, however, say the benefit of rewetting peat bogs for carbon storage needs more study. For instance, a 2021 study done in Europe compared 320 rewetted bogs with 243 near-natural bogs. Researchers found that the rewetted bogs had more variable water tables, less organic matter, and different plant communities than the near-natural bogs. That research was done on fen peatlands, however, not pocosins, which are found only along the U.S.’ southeastern coastline.
Pocosins were severely altered starting in the 1700s, when people began building canals along the North Carolina coast to lower the water table and convert pocosin land for forestry and farming. Today there are about 11,000 miles of canals, which have turned many of the bogs from carbon sinks into carbon sources. “They drained and drained and drained and drained,” Richardson said. “But some of that land has not been very successfully farmed, because it’s too low and there’s been saltwater incursion.”
Richardson and his coauthors conducted field experiments at Pocosin Lakes National Wildlife refuge in eastern North Carolina and on a privately owned tract of drained peatland to gauge how effectively the carbon storage capabilities of the drained bogs could be restored. They blocked drainage to the canals and put in small dams to help retain rainwater in the soil. They sampled greenhouse gases coming off drained pocosins and found that by raising the water table from 60 centimeters beneath the surface in drained sites to 30 centimeters beneath it, they reduced carbon losses by 94%.
Despite the bogs’ carbon storage superpower, Richardson said there may need to be higher carbon credit payments than currently available to convince private landowners to convert their fallow farmland back into peat bogs. He estimated the cost of putting the structures in place to rewet a 10,000-acre plot at between $2 million and $3 million. Not all drained bogs can be restored; plot size, depth of peat, and even the status of nearby properties must be considered.
“If your neighbor is worried about flooding,” he said, “you might have to build berms around your property, and all of sudden the project is no longer profitable.”
Government and private industry incentives in European countries have helped move peat bog restoration projects forward faster than in the U.S. For instance, the Netherlands has created a certified revenue model for the rewetting of its peatlands. And in Scotland, the government and other organizations have provided $50 million to restore about 123,000 acres of peat bogs.
“Europe is way ahead of us,” Richardson said. “England, Scotland, Ireland, Finland, Germany are all doing really great work restoring peatland.”
The U.S. needs to catch up, he said. Not restoring drained peatlands allows the bogs to slowly emit carbon, and also makes them vulnerable to catching fire, which can release their stored carbon quickly.
“We had a big fire in June in North Carolina on private land that wasn’t rewet,” said Richardson. “It let loose millions of tons of carbon dioxide.” Some of his research plots were destroyed in the fire.
This story corrects the size of the Scottish peat bog restoration to 123,000 acres.