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RESEARCH PRODUCT

Accounting More Precisely for Peat and Other Soil Carbon Resources

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In the context of “recarbonization”, it is important to know where the soil C stocks are located and how much of these are prone to emission to the atmosphere. While it may appear to be a trivial question considering available global estimates and maps, yet there is a strong need to emphasize that erroneous estimates are made in assessing the global soil C stocks. Without doubt, peatlands hold the single most important soil C stock at the global scale, and these soils are mostly located in the northern latitudes between 50°N and 70°N. However, there are additional wetlands or other ecosystems which also hold potentially relevant amounts of soil C stocks. From the soil science perspective, it implies that there are other hydromorphic soils, besides Histosols and potentially other soil types, also containing relevant amounts of soil C stock. Differences in scientific approaches, which include terminology, definitions, depth to which soil C is considered, and bulk density, etc., lead to different estimates of soil C stocks. Recent estimates indicate that peatlands cover only 3% of the global land surface but contain 40% of the soil C stocks to 1-m depth. Consequently, only small differences in the estimate of the land coverage lead to great differences in the soil C stock estimates. Typically peatlands, wetlands and other ecosystems rich in soil C, cover only small parts of the landscapes, and yet are not easily accounted for by any inventory or mapping attempts. With estimates presented in this chapter, hydromorphic soils, aside Histosols, add 10% soil C stock to the estimates of peatland’s Histosols. Additionally, non hydromorphic Podzols add another 10% to the soil C stock. Above all, soils from the steppe biome must also be considered. The soil C stock of Cryosols (frozen soil C not separated from peatlands) contain as much as 1,500 Pg C, which is as much C as the total stock estimated in world soils to 1-m depth. Thus, coordinated and substantial efforts are needed to improve the mapping of ecosystems, particularly of those which are rich in soil C stocks. One option is to improve remote sensing techniques for wetlands. These efforts must be undertaken quickly because soil C stocks are being depleted not only by the positive feedback with the climate system but also directly by land use change. The conversion of peatlands to agricultural and forestry uses is not sustainable because of the depletion C stocks, and especially not for conversion of peatlands for “biofuels” production.