wise use of mires and peatlands - Peatland Ecology Research Group
wise use of mires and peatlands - Peatland Ecology Research Group
wise use of mires and peatlands - Peatland Ecology Research Group
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VALUES AND FUCTIONS OF MIRES AND PEATLANDS75bogsfensCO 2sequestration (kg C ha -1 year -1 ) -310 -250CH 4emission (kg C ha -1 year -1 ) 53 297N 2O emission (kg N ha -1 year -1 ) 0.04 0.1Global Warming Potential 20 years 723 5524Global Warming Potential 100 years 45 1724Global Warming Potential 500 years -233 173Table 3/15: Global Warming Potential (GWP in kg CO 2-C-equivalents ha -1 year -1 ) <strong>of</strong> pristine<strong>mires</strong> using different time scales 179 .with respect to their carbon dioxide, methane<strong>and</strong> nitrous oxide balance. Over a 500-yeartime-scale pristine bogs have a negativeglobal warming potential <strong>and</strong> fens a smallpositive potential.Although it should be recognised that thereare large uncertainties in these calculations,we may provisionally conclude that■■■under the present climatic conditions,on a time scale relevant for currentcivilisation, <strong>and</strong>with respect to the combined effects <strong>of</strong>carbon dioxide, methane <strong>and</strong> nitrous oxideexchange,pristine <strong>mires</strong> play an insignificant role withrespect to global warming. In this respect,<strong>mires</strong> do not differ from virgin tropicalrainforests <strong>and</strong> other types <strong>of</strong> “climax”ecosystems that are in equilibrium withclimate. Similar to these other ecosystemtypes that have a large carbon store in theirbiomass, <strong>mires</strong> <strong>and</strong> peatl<strong>and</strong>s have aconsiderable climatic importance as stores <strong>of</strong>carbon, especially in their peat.Recently it has been acknowledged that manyother greenho<strong>use</strong> gases are emitted by <strong>mires</strong>including■Hydrocarbons that may significantlyimpact ozone, methane <strong>and</strong> carbon■■monoxide in the troposphere. Plants,primarily trees, emit an amount equivalentto all methane emissions. As the emissionsare sensitive to temperature, the emissionsfrom peatl<strong>and</strong>s in North America <strong>and</strong>Eurasia are expected to significantlyincrease under global warming.Dimethyl sulfide (DMS CH 3SCH 3), an “antigreenho<strong>use</strong>gas” that enters thetroposphere <strong>and</strong> is oxidised there to sulfateparticles, which - as cloud condensationnuclei - influence cloud dropletconcentrations, cloud albedo <strong>and</strong>consequently climate.Methyl bromide (CH 3Br) <strong>and</strong> methylchloride (CH 3Cl) that have a cooling effectthrough their ability to destroystratospheric ozone.No quantitative information is available onthe global climatic effects <strong>of</strong> thesesubstances.The role <strong>of</strong> drainage - agriculture: Whenvirgin peatl<strong>and</strong>s are converted to agriculture,the natural biomass is replaced by cropbiomass. This may result in substantialchanges in the biomass carbon store, e.g.when tropical forested peatl<strong>and</strong>s areconverted to vegetable or rice fields. Achange <strong>of</strong> non-forested virgin peatl<strong>and</strong> tograssl<strong>and</strong>s <strong>and</strong> arable fields will generally notlead to such large biomass or litter changes.
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