Study reveals peatlands may have less capacity to store carbon than predicted
A new study has revealed that peatlands may break under their own weight before they reach their carbon storage potential.
Engineers from the University of Nottingham’s Faculty of Engineering used simulation modelling to reveal the physical limitations of peatland carbon storage and showed that as peat becomes thicker and heavier, it can crack, move or slide, with many peatlands already at or beyond their modelled limits of mechanical stability.
Peatlands are carbon-rich wetlands which occupy 3% of the global land surface and 12% of UK land area. They are formed over thousands of years as moss, roots and stems create layers in wet ground locking in the carbon.
This study published in Scientific Reports has revealed that that the weight of these layers can cause instability especially in sloping areas and that peatlands may only expand to 1.48 times their current volume, not the 1.71 that existing carbon projections assume – this represents a large quantity of carbon that may never be stored at all.
For the experiment the team created a computer modelled peatland covering around 500 metres near to a river. The model featured a flat upland, a slope in the middle and a lowland running down to the water. Rainfall, water drainage and plants growing and dying were added to the simulation and peat gathered on a smooth, watertight base.
They repeated the simulation adjusting the middle slope by one-degree margins taking the angle from 0 to 12 degrees, the model tracked the forces building inside the pile over a simulated time period of thousands of years and when the forces beat the strength of the peat, that depth was recorded.
Professor David Large form the Faculty of Engineering led the study, he explains: “Our comparison with UK peat-depth data indicates that many of our peatlands are already at or beyond their modelled limits of mechanical stability. This is relevant to restoration and carbon-credit schemes such as the IUCN UK Peatland Code. Peat depth, slope and stability may need to be considered when assessing whether carbon benefits will be secure over the long term.”
The research also noted that whilst rewetting remains essential for restoring damaged peat and reducing carbon emissions, the resulting changes in water levels and water movement could affect mechanical stability in some settings, particularly in deep peat or on slopes, so this risk should be assessed as part of restoration planning.
Professor David Large adds: "Many peatlands may be closer to their natural storage limits than previously recognised, because the weight of the peat itself can eventually cause instability, erosion and carbon loss.
“This research demonstrates the need to consider peat depth, slope and stability when assessing whether carbon benefits will be secure over the long term.”
Journal
Scientific Reports
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Mechanical thresholds constrain global peatland carbon accumulation
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