Mire

A mire (or quagmire) is a wetland type, dominated by living, peat-forming plants. Mires arise because of incomplete decomposition of organic matter, usually litter from vegetation, due to water-logging and subsequent anoxia. All types of mires share the common characteristic of being saturated with water at least seasonally with actively forming peat, while having its own set of vegetation and organisms. Like coral reefs, mires are unusual landforms in that they derive mostly from biological rather than physical processes, and can take on characteristic shapes and surface patterning.Mires, although perhaps at their greatest extent at high latitudes in the Northern Hemisphere, are found around the globe. Estimating the extent of mire land cover worldwide is difficult due to the varying accuracy and methodologies of land surveys from many countries. However, mires occur wherever conditions are right for peat accumulation: largely where organic matter is constantly waterlogged. The distribution of mires therefore depends on topography, climate, parent material, biota and time. The type of mire - bog, fen or swamp - depends also on each of these factors.Mires have unusual chemistry, which influences inter alia their biota and the chemistry of the water outflow. Peat has very high cation-exchange capacity due to its high organic matter content: cations such as Ca2+ are preferentially adsorbed onto the peat in exchange for H+ ions. Water passing through peat declines in nutrients and in pH. Therefore mires are typically nutrient-poor and acidic unless the inflow of groundwater (bringing in supplementary cations) is high.Mires are used by humans for a range of purposes, the most dominant being agriculture and forestry, which accounts for around a quarter of global peatland area. This involves cutting drainage ditches to lower the water table with the intended purpose of enhancing the productivity of forest cover or for use as pasture or cropland. Agricultural uses for mires include the use of natural vegetation for hay crop or grazing, or the cultivation of crops on a modified surface. In addition, the commercial harvest of peat from mires for energy production is widely practiced in Northern European countries, such as Russia, Sweden, Finland and the Baltic states.The global distribution of tropical mires is mostly concentrated to Southeast Asia where agricultural use of peatlands has been developed in recent decades. Large areas of tropical peatlands have been cleared and drained for food and cash crops such as palm oil plantation. Large scale drainage of these plantations often results in subsidence, flooding, fire and deterioration in soil quality. Small scale encroachment on the other hand, is linked to poverty and is so wide spread that it as well has a negative impact on these peatlands. The biotic and abiotic factors controlling the Southeast Asian peatlands are completely interdependent. Its soil, hydrology and morphology are created by the present vegetation through the accumulation of its own organic matter where it builds a favorable environment for this specific vegetation. This system is therefore vulnerable to changes in hydrology or vegetation cover. Furthermore, these peatlands are mostly located in developing regions with impoverished and rapidly growing populations. The lands have there for become target for commercial logging, paper pulp production and conversion to plantations through clear-cutting, drainage and burning. Drainage of tropical peatlands alters the hydrology and increases their susceptibility to fire and soil erosion, as a consequence of changes in physical and chemical compositions. The change in soil strongly effects the sensitive vegetation and forest die-off is common.  The short-term effect is a decrease in biodiversity but the long-term effect, since these encroachments are hard to reverse, is a loss of habitat. Poor knowledge about peatlands sensitive hydrology and lack of nutrients often lead to failing plantations where pressure increases on remaining peatlands.Wetlands provide an environment where organic carbon is stored in living plants, dead plants and peat, as well as converted to carbon dioxide and methane. Three main factors giving wetlands the ability to sequester and store carbon are the high biological productivity, high water table and low decomposition rates. Suitable meteorological and hydrological conditions are necessary to provide an abundant water source for the wetland. Fully water-saturated wetland soils allow anaerobic conditions to manifest, storing carbon but releasing methane.Rehabilitation projects undertaken in North America and Europe usually focus around the rewetting of peatlands and revegetation with native species. This acts to mitigate carbon release in the short term, before the new vegetation growth provides a new source of organic litter to fuel the peat formation process in the long term.