wise use of mires and peatlands - Peatland Ecology Research Group

42 MIRES AND PEATLANDSJoosten & Succow 2001.33Adapted from Couwenberg & Joosten 1999.34Sjörs 1948.35Cf. Succow 1982.36Cf. Wassen & Joosten 1996, Sirin et al. 1997,1998a.37Joosten 1997.38Sensu Couwenberg & Joosten 1999.39Joosten 1993.40Johnson & Damman 1991.41Cf. Wolejko & Ito 1986, Damman 1995.42Agnew et al. 1993, Shearer 1997, personalcommunication from Ton Damman.43Kaffke et al. 2000.44Rieley & Page 1997.45Cf. Driessen & Rochimah 1976; pers. comm.Herbert Diemont 1998.46Examples include plateau bogs, concentric bogs,eccentric bogs, aapa fens etc. The origin anddevelopment of these striking patterns is stillsubject to considerable debate, particularly withregard to the processes that control them (seereviews in Glaser 1999 and Couwenberg & Joosten1999).47Alexandrova 1988.48Cf. Tarnocai & Zoltai 1988, Glooschenko et al.1993.49Jeschke et al. 2001.50Polygon mires are therefore a subtype of thewater rise mire type.51Tarnocai & Zoltai 1988, Glooschenko et al. 1993.52For a review, see MacKay 1998.53Åhman 1977, Zoltai et al. 1988, Glooschenko etal. 1993.54Blyakharchuk & Sulerzhitsky 1999.55Initial ice formation in surficial peat leads to aninitial raising of the surface, because ice has morevolume than a similar mass of water. As the moreelevated elements get a thinner snow cover theyare consequently less insulated in winter, and theice nuclei thus get colder and expand. The driersurficial moss layer of the elevated elementinsulates the ice core against thawing in summer(Glooschenko et al. 1993). The formation of icein the elevated elements also decreases theirhydraulic conductivity (Glooschenko et al. 1993)and has a similar effect on pattern formation tothat of stronger decomposition (cf. Couwenberg& Joosten 1999).56Glooschenko et al. 1993, Jeschke et al. 2001.57See also Appendix 1. Methodological remarks:See Joosten 2002 for a detailed presentation anddiscussion of the basic data. For internationalcomparison, existing data have been adjusted to auniform standard. In this inventory (cf. §2.1)‘peatlands’ are areas with a minimum peat depthof 30 cm; peat consists of at least 30% (dryweight) organic material; ‘mires’ are peatlandswith actual peat accumulation. The first criterion(depth of 30 cm.) excludes many (sub)arctic areaswith a shallow peat layer, the second criterion isconsistent with common definitions and does notgreatly affect the inventory results. Because everypeatland is or has been a mire, the formeroccurrence of mires have largely been reconstructedfrom the extent of peatlands and peat soils. Forthe ‘original occurrence’, the maximum mireextent in every region during the Holocene hasbeen used. Applying a fixed time slice would havebeen complicated, as mires were already beingdestroyed in some regions, very early andextensively, while still expanding in other places.There are no indications that a substantial area ofmires disappeared naturally since the Holocenemaximum. Anthropogenic losses (losses due tohuman activity) also include indirect effects, e.g.consequent hydrological changes outside the mirearea itself. Peat subsidence, oxidation, and erosionfollowing human activities have changed manyformer peatlands into mineral soils according togeological or pedological definitions, excludingthem from recent inventories. These sources oferror have been corrected for by taking historicland use intensity into account. Human activitieshave not only led to a destruction of mires, butalso to their origin and expansion (Moore 1975,Törnqvist & Joosten 1988). It is difficult to judgeto what extent these processes would have takenplace without human interference (cf. Moore1993). For this reason these possible ‘constructive’activities have not been balanced with those of a‘destructive’ nature. National borders have beenchanging considerably in the 20th century,particularly in Central Europe, complicating theuse of older inventories. The figures of lossespresented here are to a large extent“guesstimates”, as adequate data are not availablefor the majority of countries. Available data arelargely out-of-date, inconsistent, and difficult tocompare. This applies to peatlands in general, butespecially to mires. Little doubt can, however,exist about the order of magnitude and the trendof the changes. Data for different types of miresare even more difficult to obtain on a global scale,because of non-compatible classification systemsand typologies.58“Many of the data on peat resources are publishedon the basis of undisclosed modes of computation.Field mapping, coring, and analyses are ofteninadequate or wholly lacking, so that the publishedvalues for such cases should be considered as wellintentionedspeculations rather than as reliablegeological data.” (Fuchsman 1980).59Most recent world-wide overview Lappalainen1996. See also Rubec 1996, Zoltai & Martikainen1996.60The absence of reliable data on the actual mireand peatland resource and its recent changesunderlines the necessity for further inventory, asrecommended by the 6th and 7th Conferences ofthe Contracting Parties of the Ramsar Conventionand the Global Action Plan for Peatlands Theme1.61The map is taken from Lappalainen 1996.62Gorham 1991.63Lappalainen 1996. Tables A1/1 to A1/5 inAppendix 1.64Joosten, 1999, Safford and Maltby, 1998.65Vitt and Halsey 1994, Oeckel et al. 1993, 1995,Malmer & Wallén 1996, Vompersky et al. 1998,