Archaea
“Last year’s rise was the biggest increase since global methane levels started rising again in 2007.
The majority of it was from natural sources.
“If you increase the amount of precipitation in the areas of the wetlands, and if you increase the temperature, then these methane producing bacteria, produce more methane,” said Dr Oksana Tarasova from the WMO.”
https://www.bbc.co.uk/news/science-environment-59016075
If the BBC would like to check the facts, they might find that Methane comes about as a waste product of methanogenic Archaea. Not from Bacteria.
It is now thought that the weight of Archaea outweighs all other living things, not really something that humans have much control over.