Greenhouse gas emissions from wetlands

Greenhouse gas emissions from wetlands of concern consist primarily of methane and nitrous oxide emissions. 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.^[1][2][3] Wetlands account for approximately 20–30% of atmospheric methane through emissions from soils and plants, and contribute an approximate average of 161 Tg of methane to the atmosphere per year.^[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. This high level of water saturation creates conditions conducive to methane production. Most methanogenesis, or methane production, occurs in oxygen-poor environments. Because the microbes that live in warm, moist environments consume oxygen more rapidly than it can diffuse in from the atmosphere, wetlands are the ideal anaerobic environments for fermentation as well as methanogen activity. However, levels of methanogenesis fluctuates due to the availability of oxygen, soil temperature, and the composition of the soil. A warmer, more anaerobic environment with soil rich in organic matter would allow for more efficient methanogenesis.^[5]

Some wetlands are a significant source of methane emissions^[6][7] and some are also emitters of nitrous oxide.^[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.^[10] Wetlands can also act as a sink for greenhouse gases.^[11]