It’s no secret that trees are critical to preserving the planet. They produce the air we breathe, sequester carbon dioxide from the cars we drive, and provide structure to the soil that grows our food. Some fascinating discoveries on the biological process occurring within trees have led scientists to uncover some exciting implications in reducing global greenhouse gas emissions.
In 2018, scientists found that along with the oxygen trees produce through photosynthesis, trees emit methane, a greenhouse gas at least 34 times more potent than carbon dioxide. The research showed that the levels at which dead trees emit methane is up to eight times more than that of live trees, meaning that trees are a large methane sink. These levels were found in countries and regions worldwide, including Japan, the U.S., China, France, the U.K., and the Amazon basin. Almost 50% of its methane emissions could be attributed to trees. What was still unknown was how the trees maintained their levels of methane emissions.
The climate science sector got an answer early last year when a team of geoscientists from the Southern Cross University in Australia discovered large communities of bacteria living within the bark of a common tree in Australia called the Paperbark tree. The bacteria, called high-affinity methanotrophs (HAMs), are known for living in methane-rich environments and surviving by consuming methane. In this particular tree species, scientists found that nearly 25% of the tree’s bacterial flora included these methane-eating bacteria. When they took samples for testing, they observed that the HAMs reduced methane levels by 36%. Similarly, the chemical processes that HAMs undergo to consume methane produce carbon dioxide, a key component in photosynthesis.
Thankfully, these bacteria are not limited to just one specific tree in the heart of Australia. In a separate study from Purdue University, researchers found HAMs active in ecosystems worldwide. They range from wetland ecosystems, estimated to make up between 20 and 31% of the world’s methane emissions, to the Arctic, which has recently become noteworthy for rising methane levels due to the thawing of permafrost.
HAMs represent a tremendous breakthrough in climate research focusing on the methane cycle. The discovery helps scientists understand and account for the disparities in emissions in parts of the world where predictions were off by a significant margin, particularly in regions like the Arctic, where previously observed levels of methane were between five and 10 gigatons lower than estimated levels. Scientists also see HAMs as a possible way to curb methane levels in areas like Siberia, where methane levels have spiked by up to nine times previous levels.
Researchers also see methanotrophs as a possible key to large-scale reforestation projects. Because the bacteria can convert methane into less harmful carbon dioxide, they can provide young saplings with the food they need to thrive.
While the mechanisms by which these bacteria thrive and work are not deeply understood yet, the possibilities on the horizon offer exciting opportunities.