According to a study published in NatureTree bark surfaces play a key role in removing methane from the atmosphere. While trees have long been known to benefit the climate by removing carbon dioxide from the atmosphere, this new study suggests a surprising additional benefit to the climate. Microbes hiding in tree bark can absorb methane, a potent greenhouse gas, from the atmosphere.
An international team of researchers led by the University of Birmingham has shown for the first time that microbes living in tree bark or the wood itself can remove atmospheric methane on a scale equal to or greater than that in soil. They estimate that this newly discovered process makes trees 10 per cent more beneficial to the climate than previously thought.
The impact of methane and the contribution of trees
Methane is responsible for about 30 percent of global warming since the pre-industrial era, and emissions are increasing faster than at any time since records began in the 1980s.
While most methane is removed by processes in the atmosphere, soils are full of bacteria that absorb the gas and break it down to use as energy. Soil was thought to be the only reservoir of methane on land, but now researchers show that trees may be just as important, if not more so.
Lead researcher on the study, Professor Vincent Gauci from the University of Birmingham, said: “The main way we look at the contribution of trees to the environment is by absorbing carbon dioxide through photosynthesis and storing it as carbon. But these results reveal a surprising new way in which trees provide a vital climate service.
“The Global Methane Commitment, launched at the COP26 climate change summit in 2021, aims to reduce methane emissions by 30 percent by the end of the decade. Our results show that planting more trees and reducing deforestation must be an absolutely essential part of any approach to this goal.”
Methane absorption depends on forest type
In the study, the researchers looked at high-altitude tropical, temperate, and boreal forest trees. Specifically, they took measurements in the rainforests of the Amazon and Panama; temperate broadleaf trees in Wytham Woods, Oxfordshire, United Kingdom; and a boreal coniferous forest in Sweden. Methane uptake was strongest in the rainforests, likely because microbes thrive in the warm, humid conditions found there. On average, the newly discovered methane uptake accounts for about 10% of the climate benefits provided by trees in temperate and tropical climates.
By studying the exchange of methane between the atmosphere and the tree bark at different altitudes, they were able to show that trees at ground level probably release small amounts of methane a few meters above in the direction of exchange and methane is consumed from the atmosphere.
In addition, the team used laser scanning techniques to measure the total global bark surface area of forest trees; preliminary estimates suggest that the total global contribution of trees is 24.6–49.9 Tg (million tonnes) of methane. This fills a major gap in our understanding of global methane sources and sinks.
Analysis of the tree’s shape also shows that if all the bark from all the trees in the world were laid flat, the area would be equal to the Earth’s surface. “Wooden surfaces add a third dimension to how life on Earth interacts with the atmosphere, and this third dimension is full of life and surprises,” said co-author Yadwinder Malhi of the University of Oxford.
Professor Gauci and colleagues at Birmingham are now planning a new research programme to find out whether deforestation is leading to higher methane concentrations in the atmosphere. They will also try to learn more about the mechanisms used by the microbes themselves to absorb methane, and whether the removal of methane from the atmosphere by trees can be improved.
Source: Port Altele
