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Carbon dioxide is a well-known greenhouse gas that traps heat in Earth's atmosphere. This heat contributes significantly to global warming. Trees have long been celebrated for their ability to capture and store this carbon as they grow through photosynthesis. However, scientists now report that trees perform an even more critical function than previously understood. Beyond their leaves, the bark of trees hosts a vast community of microbes. These microscopic organisms absorb other major climate-altering gases. These tiny life forms are capable of devouring hydrogen, methane, and carbon monoxide. These gases play complex roles in Earth's thermal balance.
The significance of removing methane cannot be overstated. Over a 100-year period, methane is responsible for 28 times more warming potential than carbon dioxide. While carbon monoxide and hydrogen are less potent individually, they indirectly accelerate global warming. They do this by extending the lifespan of methane in the atmosphere. When these gases persist, they trap more heat. This leads to more rapid climate shifts. Therefore, removing them is a significant, albeit hidden, benefit of trees. Luke Jeffrey, a biogeochemist at Southern Cross University in Lismore, Australia, studies how chemical compounds move through the environment. Until this recent research, scientists were unaware that bark microbes were actively drawing down these invisible atmospheric threats.
This community of microscopic life is known as the bark microbiome. It is staggering in both size and complexity. Jeffrey and his colleagues estimate that approximately 6 trillion microbes inhabit every square meter of tree bark. To visualize the sheer scale, consider that there are an estimated 41 million square kilometers of tree bark worldwide. This surface area is vast enough to cover both North and South America combined. Despite this enormous presence, the activity of these microbes remained hidden in plain sight for centuries. Jonathan Gewirtzman, a forest ecologist at Yale University in New Haven, Connecticut, notes that this discovery highlights how little we actually know about the bark. He states that the sheer volume of microbial life suggests that bark is not merely a protective shell. It is an active biofilter for the atmosphere.
The investigation into this phenomenon began with a specific focus on methane. Chris Greening, a microbiologist at Monash University in Melbourne, Australia, collaborated with Jeffrey. They wanted to understand how this potent gas interacts with the environment. Methane is responsible for approximately one-third of human-caused climate warming. It naturally bubbles up from microbes living in the waterlogged sediments of lakes and wetlands. Often, it finds its way into the atmosphere.
For years, scientists had measured methane rising from the flooded lowlands of the Amazon rainforest. They noticed that the amount of gas escaping the ground was only about half of what their models predicted. This "missing" methane puzzled researchers for decades. Then, in 2017, a team of scientists realized that the missing gas was not disappearing. Instead, it was seeping out of the trunks of Amazonian trees. At the time, the prevailing theory was that the trees were acting like chimneys. They pulled methane from the soil and released it into the air. This suggested that trees were contributing to the greenhouse effect rather than mitigating it.