Trees Have an Extra Benefit

We are all familiar with the somewhat controversial proposition that our greatest effort to combat climate change, or climate crisis as it is called in recent years, is planting trees. Trees, through photosynthesis, convert carbon dioxide in the atmosphere into various hydrocarbon chains such as cellulose, lignin, and similar hard substances. Thus, they function as carbon sinks as they lignify. When a tree dies in temperate climates, it is slowly broken down by microorganisms -especially fungi- and mixes into the soil. Organic matter from dead trees accumulates in the soil and forms a thick layer of humus, which traps atmospheric carbon in the soil and keeps it there.

Various arguments stand against the theory that the climate crisis can be halted if we plant enough trees. For example, some argue that steppe plants absorb carbon much faster than trees. Thus we should protect steppes and expand them in damaged lands in a way that does not disrupt the natural ecosystem of the region – rather than planting trees. Besides, most afforestation projects, especially ambitious ones that aim to plant a large number of trees in a short time, create artificial plantations instead of natural forests. These usually become filled with a single species and may cause more harm than good in the long term, as one of the most important characteristics of a healthy forest is the biodiversity it has and supports.

To add a brief information; according to the Guinness Book of Records, the record for planting the largest number of trees by a single person in 24 hours belongs to Antoine Moses, a young Canadian who carried out the work on 17 July 2021. Moses alone planted 23,060 trees in 24 hours. This means planting a tree sapling every 3.75 seconds. The record for the most trees planted by a team in one hour, on the other hand, was set by the Chief Forest Officer of Assam State in India on 25 September 2023. Within the scope of the project, a total of 331,929 trees were planted in 1 hour.

Back to our topic… Although carbon dioxide is the main actor of the climate crisis, we should not forget methane, which is also a greenhouse gas. We release methane into the atmosphere in much lower amounts, but is 28 times more powerful than carbon dioxide. Even though it is an important gas that keeps our planet at habitable temperatures (making up only 0.00017% of the atmosphere), it is held responsible for 30% of climate change and the officials state that the concentration of methane in the atmosphere has increased by 160% after industrialisation due to anthropogenic activities. However, the life of methane gas in the atmosphere is about 10 years, about 95% is decomposed by oxidation, and the remaining 5% is consumed or transformed by methanotrophic microorganisms in the soil –which feed on methane.

We have already mentioned that trees, more precisely forests, are sinks for carbon dioxide. Scientists from the University of Birmingham in the UK have uncovered another unexpected aspect of trees: They also function as methane sinks thanks to the microorganisms living in their trunks and barks. According to estimates, this makes trees 10 percent more effective in combating the climate crisis. Researchers conducted studies in tropical (Amazon and Panama), temperate broadleaf (UK) and subarctic coniferous forests (Sweden) and found that methane absorption is most intense in the tropical climate due to hot and humid conditions. They determined that trees release some methane gas at the soil level, which was already known, but start absorbing methane 1-2 metres above.

According to the team’s tree form analysis, if the bark of all the trees on Earth were flattened and laid on the ground, it would cover the entire planet. Based on this calculation, the amount of methane gas absorbed from the atmosphere by the trees is thought to be 24.6-49.9 million tonnes. This is close to the amount soil microorganisms absorb from the atmosphere.

In 2021, another study found methanotrophic bacteria in the bark of an Australian tree called Melaleuca quinquenervia in Latin.

According to Vincent Gauci, a researcher at the University of Birmingham, “The Global Methane Pledge, launched in 2021 at the COP26 climate change summit aims to cut methane emissions by 30% by the end of the decade. Our results suggest that planting more trees and reducing deforestation surely must be important parts of any approach towards this goal”