Greenhouse-gas emissions from inland waters modulated by wetlands: African systems with a special focus on Congo

Wetlands are fundamental elements in the global carbon cycles, acting as a long-term sink of organic carbon below ground and at the same time as the largest natural source of CH4 to the atmosphere. Wetlands are often contiguous to river channels, and have been shown to affect both CO2 and CH4 riverine emissions. Here we discuss the role of tropical wetlands in driving CO2 and CH4 fluxes based on data collected in 12 rivers in Sub-Saharan Africa acquired during >30 field expeditions and additional seasonally resolved sampling at >30 sites between 2006 and 2014. Riverine CO2 and CH4 emissions were directly correlated to wetland coverage and aboveground vegetation biomass, implying that future changes in wetland and upland vegetation cover will strongly impact GHG emissions from African inland waters. We also compare the behavior of CO2 and CH4 in the two largest rivers in the World (Amazon and Congo) and we attribute the different behavior of CH4 in these two rivers to differences in connectivity between river channels and wetlands.