wise use of mires and peatlands - Peatland Ecology Research Group

202 APPENDIX 2nomadic agriculture, of agricultural residues,and of biomass as fuel for cooking andheating 88 .Peatland fires may lead to the ignition of thepeat layers, especially after drainage 89 . Suchfires are difficult to extinguish and may lastfor many months despite extensive rains. Thedepth and extent of such fires depend on theoxygen availability, the moisture content, andthe presence of cracks in the peat 90 .Emissions from biomass and peatlandburning represent a large perturbation ofglobal atmospheric chemistry 91 . In the 1982-3 drought and fire in East Kalimantan, thearea affected by fire included 5500 km 2 of peatswampforest 92 . In 1997 and 1998 landclearance activities in Indonesia combinedwith an extended dry season created severalmonths of forest and peatland fires. Two ofthe most intensive sources of smoke andparticulate matter were fires on the peatlandsof Kalimantan and Sumatra. Both the surfacevegetation and the underlying peat wereignited. In Kalimantan some 7500 km 2 of peatswampforest was destroyed with a loss ofsurface peat of between 0.2 and 1.5 metres.Total emissions of carbon as a result of thefires are estimated at between 400 10 12 g Cand 900 10 12 g C 93 , being equal to 10 % of theglobal annual emission from fossil fuelconsumption 94 .A2.8 THE ROLE OF PEATLANDINUNDATION AND REWETTINGPeatlands are inundated for rice cultivation 95 ,water reservoirs (especially for hydroelectricity96 ), and mire restoration. Higherwater table depths generally lower the carbonmineralisation rate 97 . Nevertheless inundationand rewetting do not necessarily result inlower emission rates.Rice paddies are among the most importantCH 4emitters in the world 98 . Inundation ofpeatlands to create water reservoirs leads tosignificant emissions of both CO 2and CH 499.Roulet (2000b) estimates the emission fromCanadian wetlands due to flooding to beapproximately 1x10 12 g C y -1 , representing 5%of Canada’s anthropogenic emissions.The rewetting of degraded peatlands wouldalso generally be expected to lead to adecrease in CO 2- and N 2O emissions 100 . Inpractice, however, rewetting of fen grasslandsoften leads to increased CH 4emissions 101 ,while CO 2emissions may remain continuouslyhigh 102 . This could be caused by the rapiddecomposition of young plant material andis probably a transient phenomenon. Waterlevel fluctuations on such plots may cause adrastic increase of N 2O emissions 103 .Rewetting of drained alder forests leads toincreased emissions of CH 4, but to decreasingN 2O- emissions 104 .A2.9 THE EFFECTS OF CLIMATECHANGE ON MIRES ANDPEATLANDSThe distribution of mires and mire types overthe globe clearly reflects their dependenceon climate 105 . As mires are concentrated inhumid or cool regions, a changing climate canbe expected to seriously affect their carbonbalance and radiative forcing.Most climate models suggest that thenorthern regions, which contain most of theworld’s peatlands, will become significantlywarmer in the 21 st century, - continental areas(though this is less certain) becoming drierand oceanic areas becoming wetter.Since both net primary production anddecomposition are closely related to moistureand temperature, significant alterations in thecarbon dynamics of peatlands may result 106 .Some researchers stress the importance ofalterations in the water table level 107 , whichmight increase carbon accumulation innorthern peatlands but might create a greater