Termites are cause for alarming rate of Methane Emissions

Natural Sources
Emissions from natural sources are largely determined by environmental variables such as temperature and precipitation. Although much uncertainty remains as to the actual contributions of these natural sources, available information indicates that global methane emissions from natural sources are around 190 Tg per year. The figure below shows the relative contribution of different natural sources to global atmospheric methane emissions.

Source: Prepared from data contained in IPCC, 2001c .

Wetlands. Natural wetlands are responsible for approximately 76% of global methane emissions from natural sources, accounting for about 145 Tg of methane per year. Wetlands provide a habitat conducive to methane-producing (methanogenic) bacteria that produce methane during the decomposition of organic material. These bacteria require environments with no oxygen and abundant organic matter, both of which are present in wetland conditions.

Termites. Global emissions of termites are estimated to be about 20 Tg per year, and account for approximately 11% of the global methane emissions from natural sources. Methane is produced in termites as part of their normal digestive process, and the amount generated varies among different species. Ultimately, emissions from termites depend largely on the population of these insects, which can also vary significantly among different regions of the world.

Oceans. Oceans are estimated to be responsible for about 8% of the global methane emissions from natural sources, accounting for approximately 15 Tg of methane. The source of methane from oceans is not entirely clear, but two identified sources include the anaerobic digestion in marine zooplankton and fish, and also from methanogenisis in sediments and drainage areas along coastal regions.

Hydrates. Global emissions from methane hydrates is estimated to be around 10 Tg of methane per year, accounting for approximately 5% of the global methane emissions from natural sources. Methane hydrates are solid deposits composed of cages of water molecules that contain molecules of methane. The solids can be found deep underground in polar regions and in ocean sediments of the outer continental margin throughout the world. Methane can be released from the hydrates with changes in temperature, pressure, salt concentrations, and other factors. Overall, the amount of methane stored in these hydrates globally is estimated to be very large with the potential for large releases of methane if there are significant breakdowns in the stability of the deposits. Because of this large potential for emissions, there is much ongoing scientific research related to analyzing and predicting how changes in the ocean environment affect the stability of hydrates.