Greenhouse gas emissions from wetlands
Wetlands are the largest natural source of atmospheric methane in the world, and are therefore a major area of concern with respect to climate change.
[4] Wetlands are characterized by water-logged soils and distinctive communities of plant and animal species that have adapted to the constant presence of water.
[8][9] Nitrous oxide is a greenhouse gas with a global warming potential 300 times that of carbon dioxide and is the dominant ozone-depleting substance emitted in the 21st century.
[13] Wetland classes include marshes, swamps, bogs, fens, peatlands, muskegs, prairie pothole (landform),[14] and pocosins.
[15] Nitrous oxide is a greenhouse gas with a global warming potential 300 times that of carbon dioxide and is the dominant ozone-depleting substance emitted in the 21st century.
[10] Excess nutrients mainly from anthropogenic sources have been shown to significantly increase the N2O fluxes from wetland soils through denitrification and nitrification processes (see table below).
[16][8][17] A study in the intertidal region of a New England salt marsh showed that excess levels of nutrients might increase N2O emissions rather than sequester them.
[16] Data on nitrous oxide fluxes from wetlands in the southern hemisphere are lacking, as are ecosystem-based studies including the role of dominant organisms that alter sediment biogeochemistry.
[37] For example, in peatlands, the mass amount of dead, but not decaying, organic matter results in relatively slow diffusion of methane through the soil.
Ebullition in wetlands can be recorded by delicate sensors, called piezometers, that can detect the presence of pressure pockets within the soil.
Using piezometers and hydraulic heads, a study was done in northern United States peatlands to determine the significance of ebullition as a source of methane.
[40] The magnitude of methane emission from a wetland are usually measured using eddy covariance, gradient or chamber flux techniques, and depends upon several factors, including water table, comparative ratios of methanogenic bacteria to methanotrophic bacteria, transport mechanisms, temperature, substrate type, plant life, and climate.
This theory of movement is supported by observations made in wetlands where significant fluxes of methane occurred after a drop in the water table due to drought.
Plant leachates such as phenolic compounds from Sphagnum can also interact with soil characteristics to influence methane production and consumption.
[42] A constant availability of cellulose and a soil pH of about 6.0 have been determined to provide optimum conditions for methane production and consumption; however, substrate quality can be overridden by other factors.
Net ecosystem production (NEP) and climate changes are the all encompassing factors that have been shown to have a direct relationship with methane emissions from wetlands.
[12] However, as a result of draining, water saturated ditches develop, which due to the warm, moist environment, end up emitting a large amount of methane.
