A recent study shows that the sharp increase in atmospheric methane concentrations during the COVID-19 lockdown occurred driven by inundation and flooding of wetlands, and not as a result an air-quality improvement.
Wetlands’ Outsized Role
Published today in the journal Proceedings of the National Academy of Sciences, Dimensionality and drivers behind an unprecedented surge in atmospheric methane during this decade shows that 73% of greater wetland inundation and water storage, specifically across equatorial Asia and Africa, drove a step change in atmospheric methane between 2020-22.
Before the pandemic, methane releases have actually climbed constantly albeit slowly (indicated by the thick line), but 2020-2022 raised substantially more than previous years (from approx. 499 teragrams [Tg] to 570-590 Tg). This rapid increase, says lead study author, Zhen Qu of North Carolina State University, was not mostly driven by the drop in auto emissions during pandemic lockdowns as many had hypothesized. Rather, it was the intense precipitation and flooding in critical wetland habitats.
Linking Methane to Wetlands
And Wetlands are huge emitters of the potent greenhouse gas, methane — one that is even worse for the climate change than carbon dioxide in the short term! Microbes decompose organic matter in these waterlogged environments without the presence of oxygen, emitting methane into the atmosphere.
Investigators found that more flooding and water storage in wetlands in equatorial Asia and Africa were responsible for 43% and 30% of the extra atmospheric methane, respectively, during the pandemic period. The cause is thought to be La Niña patterns that delivered intense rain to these areas from late 2020 through the beginning of 2023.
The wetland flooding had the greatest impact, but a reduction in atmospheric hydroxide (OH) levels which breaks down methane also played a smaller part (accounting for 28% of the increase).
Conclusion
The study underscores the importance of wetlands in the local and global methane cycle, and emphasizes the need to understand how changes in precipitation patterns may affect these ecosystems. If you think about the amount of wetlands and the amount of methane they release, it might be worthwhile to learn a little bit more about how all that works since limiting the intensity of climate change will probably depend on our ability to control atmospheric methane.
