Forests have role as methane sinks in addition to carbon dioxide sinks

Maanantai 5.8.2024 klo 19.54 - Mikko Nikinmaa

Methane is a very powerful greenhouse gas – nearly a hundred times more serious than carbon dioxide. It is presently estimated to cause 20-30 % of the global warming. The good thing with methane is that its half-life is much shorter than that of carbon dioxide. About 60 % of the methane production is the result of human actions, and the rest has natural causes. Leakages in fossil fuel production and use are currently probably the most important current source followed by agriculture. The agricultural methane production is almost completely caused by cattle and other ruminants. The rest of agricultural production accounts for less than 10 % of the total. Another anthropogenic methane source is (anaerobic) decomposition of landfill leachates. Naturally methane is produced especially in anaerobic wetlands by bacteria. Such wetland production is the ultimate reason for the methane “pockets” underneath the permafrost, which may be liberated to the atmosphere as permafrost melts owing to climate change. Methane-producing bacteria have been associated with trees growing in wetlands close to the moist surface.

However, it has recently been reported that trees can also consume methane – or rather bacteria living in bark. Gauce et al. report in a recent Nature article (https://doi.org/10.1038/s41586-024-07592-w) that such a methane-consuming feature of trees should be taken into account in estimating the methane equilibria. It may have significant consequences on the role of forests in climate change mitigation.