Bark microbes remove climate gases and reshape how we view trees.

Researchers found tree bark hosts microbial communities that consume methane, carbon monoxide and hydrogen, and their scaling suggests bark microbes could remove about 55 million tonnes of hydrogen from the atmosphere each year.

Researchers report that tree bark hosts active microbial communities that consume gases from the air. Over five years, teams studied bark from eight common Australian tree species and used metagenomic sequencing plus gas measurements to learn which microbes and enzymes were present and active. Bark was previously assumed to be largely inert in relation to atmospheric gases, but the work shows an active "barkosphere" interacting with methane, carbon monoxide and hydrogen. The findings were scaled up in a simple model to estimate possible global impacts. What researchers found: - Bark samples contained very dense microbial communities, with estimates up to about 6 trillion microbial cells per square metre of bark. - Metagenomic sequencing revealed genes and enzymes linked to the consumption of methane, carbon monoxide and hydrogen. - Direct gas measurements indicated these microbes were actively taking up those gases, with hydrogen removal seen consistently across species, forest types and stem heights. - Wetland trees often contained methanotrophs that consume methane, and enzymes for carbon monoxide removal were abundant, suggesting a role in air cleaning in some settings. - Scaling the observations across global tree numbers produced an estimate that bark microbes could remove roughly 55 million tonnes of hydrogen per year and that this removal might offset up to about 15% of annual human-caused methane emissions. Summary: The research expands understanding of ways trees influence atmospheric composition by revealing an active microbial layer on bark that consumes methane, carbon monoxide and hydrogen. Researchers identify next steps as determining which tree species and forest types host the most active gas-consuming microbes and how those communities respond to environmental change.