Transformation and backfilling of peatland soils and effect on CO2 emissions

Peatlands are the Earth's largest natural terrestrial carbon reservoir, storing more than 40% of all soil organic carbon. Despite their significance, damaged peatlands emerge as a major source of greenhouse gas emissions, contributing to nearly 5% of global anthropogenic CO2 emissions.Peatlands have been drained in the Three Lakes region (Switzerland). These drainage efforts were initiated to develop agricultural land use and enhance the overall quality of life in the region. While the drainage improved living conditions, it also accelerated peat decomposition. This accelerated decomposition gave rise to a loss of soil, reaching up to 4 meters at specific locations, and drastically increased CO2 emissions.Various strategies have been developed to reduce CO2 emissions from degraded peatland. Backfilling—the deposition of a mineral layer on the soil— is one promising method to mitigate CO2 emissions. Backfilling disconnects the peat from the surface soil by a mineral layer. CO2 emissions from the peat are diminished, while the surface soil can still be used for agricultural purposes.Peatlands contain very old carbon preserved by water-logged conditions that limited carbon decomposition. We measured rates and radiocarbon (C14) signals of the CO2 emissions at three locations in the Three Lakes Region to compare the amount and age of carbon emitted from drained and drained-backfilled peatland soils. First results show that the backfilled peatland soils emit less and younger CO2 than peatland soils having no backfilling. The covered peatland still continues to degrade, however at a slower pace. The overed peat contributes to about 50% of the measured CO2 emissions from the transformed sites. Further investigation will be needed to identify the spatio-temporal variability and the influence of other factors such as the groundwater table level.