For you non-chemists, the molecule in the cover picture is methane (CH₄). Climatologists consider it second to CO₂ as a green-house-gas contributing to global warming. While atmospheric CO₂ increased ~50% over the last two centuries, methane has increased ~150%.
Methane comes naturally from wetlands(swamps and marshes) and from the digestive systems of animals, in both cases produced by anaerobic (oxygen-phobic) microbes. Lighter than air, methane drifts up into the atmosphere.
Humans contribute ~60% of global methane emissions. About two thirds is microbially produced, from cattle farming, rice paddies and from garbage (refuse tips). The remainder is non-biological, escaping from oil and gas fields; methane is the main component of natural gas.
Methane hydrates to form clathrate crystals that accumulate in ice and seabed sediments. It can stay there forever, or until released by climate change or seismic events.
Methane that enters the atmosphere stays foraround10 years. Some 80% gets dissipated by natural chemical reactions. An estimated 20% re-enters the biosphere via aerobic (oxygen-dependent) microbes called methanotrophs, that use methane as their main carbon source. Methanotrophs are widespread, particularly in upper, oxygen-exposed layers of wetland, consuming most of the methane produced by anaerobes below before it even reaches the atmosphere.
Now comes something of special interest to tree-lovers and plant scientists. A just-published scientific article (Gauci2024; Univ. Birmingham commentary cited to follow) shows that tree bark hosts methanotrophic microbes that consume environmentally-significant amounts of methane. Trees reabsorb methane drifting up from the soil and may even pull atmospheric methane.
Previously (Leaf 107 https://lnkd.in/dzNku8vT) I mentioned bioactivities of tree-bark phytochemicals. For the sake of our environment, encouraging methanotrophs is an important bioactivity to include.
Further reading
🌳 Wikipedia (2024, August 1) “Greenhouse gas”. https://en.wikipedia.org/w/index.php?title=Greenhouse_gas&oldid=1237958418
🌳 Global Monitoring Laboratory(2024?) “Critical Thinking Activity: The Methane Cycle”, US Natl Oceanic Atmos. Admin. https://gml.noaa.gov/education/info_activities/pdfs/CTA_the_methane_cycle.pdf
🌳 Cai Yet al (2016) Conventional methanotrophs are responsible for atmospheric methane oxidation in paddy soils. Nat Commun 7, 11728. https://doi.org/10.1038/ncomms11728
🌳 Gauci V et al (2024) “Global atmospheric methane uptake by upland tree woody surfaces”. Nature 631,796–800. https://doi.org/10.1038/s41586-024-07592-w.
🌳 University of Birmingham (2024)"Trees reveal climate surprise - bark removes methane from the atmosphere." ScienceDaily, 24 July 2024. www.sciencedaily.com/releases/2024/07/240724123005.htm.
