Radiative Forcing and Balance of the World's Wetlands

Wetlands have been important in their radiative forcing effect on the Earth's past glacial-interglacial cycles, and evidence suggests that recent interannual variations in atmospheric methane concentrations are driven partly by climatic effects on wetland methane emissions. Methane emissions from wetlands are offset by their substantial ability to sequester carbon. We use best estimates from the literature to construct a radiative mass balance for trace gas emissions and soil carbon sequestration from the world's wetlands. We also distinguish between the static radiative balance of wetlands and their radiative forcing, with only the latter affecting climate. Large uncertainties in our estimates are particularly due to uncertainties in historical and current wetland area and soil sequestration rates in mineral-soil wetlands. Overall, we conclude that destruction of mineral-soil wetlands has likely had a global cooling effect (and vice-versa for restoration), whereas destruction of peatlands and marine-associated wetlands has had a warming effect using a 100 year global warming potential. We also emphasize the myriad goods and services that wetlands provide besides their effects on climate forcing.