Carbon storage in peatlands: A case study on the Isle of Man

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Peatlands contain about one third of the World's terrestrial carbon (C). Due to their increasing importance in the context of climate change various studies estimated regional and global carbon stocks. The greatest uncertainty in current C stock estimates is peat depth. Information on peat depth is often lacking or spatially variable, which both limit the accuracy of C stock estimates. We present measurements of peat depth on the Isle of Man and evaluate the C sink of the region. We assess the degree to which estimates of Sphagnum cover can be used to predict peat depth and we identify and quantify various uncertainties in resulting C stock estimates. Total peatland area was identified through classification of aerial photography. Peat depth and Sphagnum cover were measured on a 50m grid at four study sites in the southern hills on the Isle of Man.Peatlands at the study sites were generally shallow with low total organic carbon (TOC) contents. Peat depth seemed not to be controlled by local terrain. It is estimated that the C stored per unit area ranges from 14.7 to 22.4kgCm−2. The results provided in this study were significantly lower than in other studies, which is likely due to the land use history. The large spatial variability of peat depth resulted in large uncertainty in C stock estimates. Sphagnum proved to be important for the formation of deep peat and could potentially be used to assess the quality of peatlands. Results suggest that peatlands on the Isle of Man will likely act as a C source in the long-term if not maintained and/or restored.