A new study has uncovered that peatlands — wetlands rich in stored carbon — might not be able to hold as much carbon as previously thought, due to their own weight. Engineers from the University of Nottingham used computer simulations to explore the physical limits of peatland carbon storage. Their findings suggest that as peat accumulates, becoming thicker and heavier over thousands of years, it can crack, shift, or slide. Many peatlands, the study shows, may already be at or beyond their mechanical stability limits, which could prevent them from storing as much carbon as current projections assume. Peatlands cover about 3% of the world's land surface and make up 12% of the UK’s land area. They form when layers of moss, roots, and stems build up in wet soil, locking in carbon over long periods. The research, published in Scientific Reports, found that the weight of these layers can cause instability, especially on slopes. The study suggests that peatlands may only expand to 1.48 times their current volume, rather than the 1.71 times assumed by existing carbon storage models. This difference could mean a significant amount of carbon may never be stored. To test their findings, the researchers created a computer model of a peatland covering about 500 meters near a river. The model included a flat upland area, a sloping middle section, and a lowland leading to the water. The simulation incorporated factors like rainfall, water drainage, and the growth and decay of plants. As peat accumulated on a smooth, watertight base, the team adjusted the slope in 1-degree increments from 0 to 12 degrees. They tracked the internal forces in the peat over a simulated time span of thousands of years, recording when these forces exceeded the strength of the peat. Professor David Large, who led the study, said the findings are important for efforts to restore peatlands and for carbon credit schemes, such as the IUCN UK Peatland Code. He emphasized that peat depth, slope, and stability should be considered when evaluating the long-term security of carbon storage benefits. While rewetting — a key method for restoring damaged peatlands — is essential, the study warns that changes in water levels and movement could affect mechanical stability, particularly in deep peat or on slopes. This risk, the researchers say, should be carefully assessed during restoration planning. The study highlights that many peatlands may be closer to their natural storage limits than previously thought, due to the weight of the peat itself potentially causing instability, erosion, and carbon loss.