wise use of mires and peatlands - Peatland Ecology Research Group

MIRES AND PEATLANDS33Outside the tropics, human exploitation hasaltered 500,000 km 2 of mires so severely thatpeat accumulation has stopped completely.Peat has been and continues to be extractedto be used for the purposes outlined in § 3.4in Chapter 3. Currently new peat extractioncommences each year on some 10 km 2 ofmire 67 . The available water, nutrients, organicsoils, and space make mires also attractivefor agriculture and forestry. 80% of globalmire losses are attributable to the latter twotypes of land use (cf. Table 2/4). Prior to 1992,the global rate of mire destruction for forestryamounted to 4,500 km 2 , that for agriculture to1,000 km 2 per year 68 . These rates are an orderof magnitude larger than the mean annual mireexpansion rate during the Holocene. As aresult, the global mire resource is decreasingby approximately 0.1% net per year 69 .1000 km 2 %Agriculture 250 50Forestry 150 30Peat extraction 50 10Urbanisation 20 5Inundation 15 3Indirect losses 5 1(erosion, other)Total 490 100Table 2/4: Causes of anthropogenic mirelosses in the non-tropical world 70 .Its long history, high population pressure,and climatic suitability for agriculture havemade Europe the continent with the largestmire losses (Table 2/3). Peat has ceased toaccumulate in over 50% of the former mirearea. Almost 20% of the original mire area nolonger exists as peatland. In many Europeancountries 1 % of the original resourceremains (Table A1/1). Denmark and theNetherlands succeeded in destroying adominant landscape type almost completely.Only Latvia, Liechtenstein, Norway, Russia,Sweden, and Ukraine still have more than halfof their original mire area left (Table A1/1).The European experience shows clearly thatan abundance of mires is no guarantee of theirlong-term survival. Finland has lost 60% ofits formerly extensive mire area, largely bydrainage for forestry since the 1950s 71 .Ireland, where mires originally covered 17%of the country, has lost 93% of its raised bogand 82% of its blanket bog mire resource 72 .The mires of Polesia in Belarus and Ukraine,one of the largest continuous mire areas ofthe former Soviet Union have largely beendrained in the 1970s and 1980s 73 .Tables A1/1 to A1/5 in Appendix 1 give theestimated peatland/mire area where the peatis more than 30 centimetres thick (> 30 cmpeat) and contains more than 30% organicmaterial (> 30% organic material). The areasare given in km 2 per country or regiongrouped by continent. Total area (1998) ofeach country or region is given according toEncarta.2.5 RATES OF PEAT ANDCARBON ACCUMULATION 74Global interest related to rising atmosphericCO 2content has led to numerous attempts toascertain the role of peatlands in the globalcarbon (C) cycle as sinks for organic C 75 . Peatdeposits are characterised by a high Ccontent, about 50% of the dry organic matter.A high abundance of peat thus signals asignificant net transfer of C to the soil.In a natural state, mires accumulate C becausethe rate of biomass production is greater thanthe rate of decomposition. The accumulationof peat involves an interaction between plantproductivity and C losses through theprocess of decay, leaching, mire fires anddeposition of C into the mineral soil beneathpeat layers.