A study showing that freshwater wetlands are a significant sink for methane is published in Nature Communications this week. Wetlands are known to be the largest natural source of atmospheric methane, a potent greenhouse gas, but they may also be responsible for destroying as much as 50% of the methane they produce via anaerobic oxidation.
Anaerobic oxidation of methane is a microbial process that occurs in marine and freshwater sediments that contain very little oxygen. This process breaks down methane molecules during reactions, usually with sulphates and nitrates, resulting in energy for the microbes and less harmful waste compounds.
Samantha Joye and colleagues investigated three large freshwater wetlands in very different geographic areas of the USA (tropical, temperate and cold-temperate) and measured the rates at which anaerobic oxidation occurs. Their results suggest the rates of methane destruction are approximately 200 teragrams, which is similar to that of marine environments and certainly much higher than previously thought. Understanding the global methane budget is important for predicting how our climate will change over the next century and identifying this process will allow for the adjusting of current calculations.