The world's peatlands influence the global balance of three main greenhouse gases (GHG) ¬carbon dioxide, methane and nitrous oxide (C02, CH4, and N20). In their natural state, peatlands remove CO2 from the atmosphere via peat accumulation and emit methane. The long-term negative effect of methane emissions is smaller than the positive effect of CO2 sequestration. By sequestering and storing an enormous amount of atmospheric C02 peatlands have had an increasing cooling effect, in the same way as in former geological eras, when they formed coal, lignite and other fossil fuels. 

When peatlands are disturbed, they can become significant sources of carbon dioxide and at the same time do not totally stop emitting methane. Methane may still be released from drainage ditches and in mining operations from milled peat surfaces and peat stockpiles. Drained peatlands, especially after fertilization, can also become an important source of nitrous oxide. Peatland restoration reduces net GHG emissions to the atmosphere, certainly over the long-term. 

• Natural peatlands affect atmospheric burdens of CO2, CH4 and N20 in different ways and so playa complex role with respect to climate.

• Since the last Ice Age peatlands have sequestered enormous amounts of atmospheric C02.

• GHG fluxes in peatlands have a spatial (zonal, ecosystem, site and intersite) and temporal (interannual, seasonal, diurnal) variability, which needs to be considered in assessment and management.

• Small changes in the ecology and hydrology of peatlands can lead to big changes in GHG fluxes through influence on peatland biogeochemistry.

• In assessing the role of peatlands in global warming, the different time frame and radiative forcing of continuous CH4 emission and C02 sequestration should be carefully evaluated rather than using simple global warming potential calculations.

• Anthropogenic disturbances (especially drainage and fires) have led to massive increases in net emissions of GHG from peatlands, which now make a significant contribution to global anthropogenic emissions.

• Peatland drainage leads to increased CO2 emissions in general and an increase in 20 releases in nutrient rich peatlands. It may not always significantly reduce CH4 emissions.

• Because of the large emissions from degraded peatlands, rewetting and restoring them is one of the most cost-effective ways of avoiding anthropogenic greenhouse gas emissions.

A Variety of methods and techniques are applied for GHG flux measurement in peatlands

Peatlands disturbed by human activities often become sources of C02 but do not totally stop emitting CH4 which is released especially from drainage ditches, (Figures represent gross emissions; GHG sequestration by peat formation and vegetation growth not included) (Source: Glagolev et al. 2007)

Peatlands fires in Southeast Asia are the world's largest single source of carbon emissions Peat oxidation from degraded peatlands leads to an annual C02 emission of over 3000 million tonnes, being equivalent to more than 10% of the global fossil fuel emissions. Fires and drainage in peatlands in Southeast Asia (primarily Indonesia), which cover less than 0.2% of the world's land surface, are currently responsible for two-thirds of these global peatland emissions.

  

  

The different GHG fluxes of pristine (left) and drained (right) peatland sites (Source: Laine et al. 1996 - with changes)

Peatland emissions of methane are NOT a mejor contributor to climate change Peatlands are currently contributing 3-5% to the total global methane emISSIOns. Larger global emissions are released by agricultural activities such as grazing and rice cultivation. The emission of methane from natural peatlands is part of the natural baseline and, because of the rapid turnover time of CRt, it does not contribute to an increase in methane in the atmosphere. Peatlands have been a stable sink of atmospheric C02 over millennia and the overall climate impact of peatlands has been a net cooling.

 

Left : The emission values from cultivated peatlands show large ranges of uncertainty. The average values (dark squares), however, illustrate that restored peatlands have lower GHG emissions than drained and cultivated sites. Downward arrows represent possible additional C02 sequestration by vegetation growth and peat accumulation; the upward arrow the possible additional Cf-i4 emission under warm and wet conditions. (Source: AIm et a/. 2007)