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Peat (turf) is an accumulation of partially decayed vegetation or organic matter that is unique to natural areas called peatlands or mires. The peatland ecosystem is the most efficient carbon sink on the planet〔 because peatland plants capture the CO2 which is naturally released from the peat, thus maintaining an equilibrium. In natural peatlands, the "annual rate of biomass production is greater than the rate of decomposition", but it takes "thousands of years for peatlands to develop the deposits of 1.5 to 2.3 m, which is the average depth of the boreal peatlands".〔 One of the most common components is ''Sphagnum'' moss, although many other plants can contribute. Soils that contain mostly peat are known as histosols. Peat forms in wetland conditions, where flooding obstructs flows of oxygen from the atmosphere, slowing rates of decomposition.〔Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Chapter 1.〕 Peatlands, also known as mires,〔"The term ‘peatland’ includes mires (Joosten and Clarke 2002)."〕 particularly bogs, are the most important source of peat,〔Gorham, E. (1957). The development of peatlands. Quarterly Review of Biology, 32, 145–66.〕 but other less common wetland types also deposit peat, including fens, pocosins, and peat swamp forests. Other words for lands dominated by peat include moors or muskegs. Landscapes covered in peat also have specific kinds of plants, particularly ''Sphagnum'' moss, ericaceous shrubs, and sedges (see bog for more information on this aspect of peat). Since organic matter accumulates over thousands of years, peat deposits also provide records of past vegetation and climates stored in plant remains, particularly pollen. Hence, they allow humans to reconstruct past environments and changes in human land use.〔Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. 323-325〕 Peat is harvested as an important source of fuel in certain parts of the world. By volume, about 4 trillion m³ of peat are in the world, covering a total of around 2% of global land area (about 3 million km²), containing about 8 billion terajoules of energy. Over time, the formation of peat is often the first step in the geological formation of other fossil fuels such as coal, particularly low-grade coal such as lignite.〔(【引用サイトリンク】title=Is coal still being formed today? )〕 Depending on the agency, peat is not generally regarded as a renewable source of energy, as its extraction rate in industrialized countries far exceeds its slow regrowth rate of 1 mm per year,〔Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Chapter 7.〕 and as peat regrowth is also reported to take place in only 30-40% of peatlands.〔http://www.eurosaiwgea.org/Activitiesandmeetings/OtherEUROSAIWGEAmeetings/Documents/Estonia_energy.pdf〕 Because of this, the United Nations Framework Convention on Climate Change (UNFCCC),〔http://www.seai.ie/Archive1/Files_Misc/IEABioenergyAgreementTask38CaseStudy.pdf〕 and another organization affiliated with the United Nations classifies peat as a fossil fuel.〔http://www.un-documents.net/ocf-07.htm Today's primary sources of energy are mainly non-renewable: natural gas, oil, coal, peat, and conventional nuclear power. There are also renewable sources, including wood, plants, dung, falling water, geothermal sources, solar, tidal, wind, and wave energy, as well as human and animal muscle-power. Nuclear reactors that produce their own fuel ("breeders"), and eventually fusion reactors, are also in this category.〕 However, the Intergovernmental Panel on Climate Change has begun to classify peat as a "slow-renewable" fuel.〔http://www.worldenergy.org/publications/survey_of_energy_resources_2007/peat/704.asp〕 This is also the classification used by many in the peat industry.〔 At 106 g CO2/MJ,〔(The CO2 emission factor of peat fuel ). Imcg.net. Retrieved on 2011-05-09.〕 the carbon dioxide emission intensity of peat is higher than that of coal (at 94.6 g CO2/MJ) and natural gas (at 56.1). Peat fires have been responsible for some large public health disasters, including the 1997 Southeast Asian haze. == Peatlands distribution == In a widely cited article, Joosten and Clarke (2002) defined peatlands, or mire (which they claim are the same)〔Supported by the "Dutch Ministry of Foreign Affairs (DGIS) under the (Global Peatland Initiative ), managed by Wetlands International in co-operation with the IUCN- Netherlands Committee, Alterra, the International Mire Conservation Group and the International Peatland Society."〕〔 as, Peatlands are areas of land with a naturally accumulated layer of peat. Peatlands are found in at least 175 countries and cover around 4 million km² or 3% of the world’s land area. In Europe, peatlands extend to about 515,000 km².〔(IUCN UK Commission of Inquiry on Peatlands ) Full Report, IUCN UK Peatland Programme October 2011〕 Peat deposits are found in many places around the world, including northern Europe and North America, principally in Canada and the Northern United States. Here, too, occur some of the world's largest peatlands, including the West Siberian Lowland, the Hudson Bay Lowland, and the Mackenzie River Valley.〔Fraser, L.H. Fraser and P.A. Keddy (eds.). 2005. The World’s Largest Wetlands: Ecology and Conservation. Cambridge University Press, Cambridge, UK. 488 p. and P.A. Keddy (eds.). 2005. The World’s Largest Wetlands: Ecology and Conservation. Cambridge University Press, Cambridge, UK. 488 p.〕 The amount of peat is smaller in the Southern Hemisphere, partly because there is less land, yet South America (Southern Patagonia/Tierra del Fuego) has one of the world's largest wetlands, the vast Magellanic Moorland, with extensive peat-dominated landscapes.〔 Peat can be found in New Zealand, Kerguelen, and the Falkland Islands, Indonesia (Kalimantan (Sungai Putri, Danau Siawan, Sungai Tolak), Rasau Jaya (West Kalimantan), and Sumatra). Indonesia has more tropical peat land and mangrove forests than any other nation on earth, but Indonesia is losing wetlands by per year.〔(【引用サイトリンク】title=Waspada Online )〕 About 60% of the world's wetlands are peat. About 7% of total peatlands have been exploited for agriculture and forestry. Under proper conditions, peat will turn into lignite coal over geologic periods of time. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「peat」の詳細全文を読む スポンサード リンク
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