Tree bark removes methane from the atmosphere

A new study published in the journal Nature has found that tree bark surfaces play a crucial role in removing methane gas from the atmosphere.

While scientists have long known that trees have an amazing capacity to sequester carbon dioxide, this research reveals an additional climate benefit: microbes within tree bark can absorb methane, a greenhouse gas more potent in the short term than CO2, from the atmosphere.

“Methane is an important greenhouse gas, but the role of trees in the methane budget remains uncertain,” noted the researchers. “Although it has been shown that wetland and some upland trees can emit soil-derived methane at the stem base, it has also been suggested that upland trees can serve as a net sink for atmospheric methane.”

Trees are more beneficial than expected

The international research team, led by the University of Birmingham, has now provided clear evidence that microbes in bark or wood remove atmospheric methane on a scale comparable to or greater than that of soil. 

The scientists estimate that this newly discovered process makes trees ten percent more beneficial for the climate overall than previously believed.

Methane is responsible for nearly 30 percent of global warming since pre-industrial times, and its emissions are currently increasing at an unprecedented rate. 

Although atmospheric processes remove most methane, experts previously believed that soil bacteria which absorb and break down methane for energy are the only terrestrial methane sink. These new findings, though, unmistakably show that trees are equally or even more significant.

A vital climate service 

“The main ways in which we consider the contribution of trees to the environment is through absorbing carbon dioxide through photosynthesis, and storing it as carbon,” explained lead researcher Vincent Gauci, an expert in biogeochemistry at Birmingham. “These results, however, show a remarkable new way in which trees provide a vital climate service.”

The researchers studied upland tropical, temperate, and boreal forest trees. They measured methane exchange in tropical forests in the Amazon and Panama, temperate broadleaf trees in Wytham Woods, Oxfordshire, UK, and boreal coniferous forests in Sweden. 

Methane absorption was strongest in tropical forests, likely due to the warm, wet conditions that favor microbial activity. On average, this newly discovered methane absorption adds approximately  ten percent to the climate benefit provided by temperate and tropical trees.

Tree bark and methane removal 

By examining methane exchange between the atmosphere and tree bark at various heights, the researchers found that while trees might emit a small amount of methane at soil level, they consume methane from the atmosphere a few meters up. 

Additionally, the team used laser scanning methods to quantify the global forest tree bark surface area. Preliminary calculations indicate that the global contribution of trees to methane removal is between 24.6-49.9 Tg (millions of tons) of methane. This discovery fills a significant gap in understanding global methane sources and sinks.

The tree shape analysis also shows that if all the bark of all the trees worldwide were laid flat, the area would be equal to the Earth’s land surface. 

“Tree woody surfaces add a third dimension to the way life on Earth interacts with the atmosphere, and this third dimension is teeming with life, and with surprises,” said co-author Yadvinder Malhi, a professor of ecosystem science at the University of Oxford.

Future research directions 

Professor Gauci and colleagues at Birmingham are now planning a new research program to determine if deforestation has led to increased atmospheric methane concentrations. 

The experts also aim to learn more about the microbes themselves, the mechanisms they use to absorb methane, and whether this atmospheric methane removal by trees can be enhanced.

Surprising role of tree bark

The implications of this research are profound, suggesting that trees not only help combat climate change by absorbing carbon dioxide but also by removing methane from the atmosphere. 

This dual function underscores the importance of forest conservation and reforestation efforts. Planting more trees and protecting existing forests could play a significant role in mitigating climate change and enhancing global biodiversity.

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