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Abstract

A peatland is a type of ecosystem where carbon (C) along with nitrogen and several other elements has been accumulated as peat originating from the plant litter deposited on the site. A logical consequence of the above definition of peatlands is that they are ecosystems, which by way of nature are a sink for atmospheric carbon dioxide (CO₂). This is the case because more C is accumulated through photosynthesis than is released through respiration. As a consequence of this, organic matter accumulates as peat. The C accumulated in peatlands is equivalent to almost half the total atmospheric content, and a hypothetical sudden release would result in an instantaneous 50% increase in atmospheric CO₂. While this scenario is unrealistic, it nevertheless highlights the central role of peatlands where huge amounts of CO₂ have almost entirely been “consumed” since the last glacial maximum, but could respond differently as a result of future changes in climatic conditions. Peatlands have, hence, over the last 10,000 years helped to remove significant amounts of CO₂ from the atmosphere. A complicating factor in this respect is that in terms of the major greenhouse gases (GHGs), peatlands are not just acting as a sink for CO₂. The wet conditions that lead to the slow decomposition of organic material and enable peat accumulation to occur, also cause significant amounts of the powerful GHG methane (CH₄) to be formed. Indeed global wetlands (predominantly peatlands) are considered to be the largest single source of atmospheric CH₄ also when considering all anthropogenic emissions. Peatlands are, therefore, also a key player in the atmospheric CH₄ budget and as a result also influence the global climate.