A five-growing-season experiment found a modest methane increase when drained peat was rewetted. Emissions remained lower than in undrained reference peat, while daytime carbon-dioxide uptake increased. The peat’s drainage history and chemistry offer a possible explanation, under experimental conditions that kept water below the restored peat’s surface.
Rewetting previously drained peat increased methane emissions relative to a drained control, but the undrained reference peat emitted roughly 4–5 times as much methane on average. Daytime carbon-dioxide uptake also rose. The peer-reviewed experiment published in Scientific Reports monitored gas exchange during the 2020–2024 growing seasons. Water in the rewetted treatment remained below the peat surface, preserving a shallow oxygenated layer.[1]
At an experimental facility in the US state of Michigan, researchers studied 24 large peat blocks collected in Minnesota. The blocks were divided equally between two origins: a forested site with a long drainage history and open land that had not been drained. Four water-level treatments, each containing six blocks, compared natural reference conditions, dried reference peat, drained control peat and rewetted drained peat. Despite similar water levels, the drained and undrained materials retained different physical properties.[1]
Long drainage may have depleted easily decomposed material, limiting the substrate available for methane production after rewetting. The researchers propose this chemical mechanism as a hypothesis; changes in vegetation and other processes were not fully separated. Methane-producing microorganisms’ relative abundance alone did not explain emissions. The daylight, growing-season measurements leave the complete annual greenhouse-gas balance unresolved, and persistently flooded or heavily farmed peat may respond differently.[1]
