After reaching the atmosphere, methane causes more than 80 times the warming power of carbon dioxide over the first 20 years. While CO2 has a longer-lasting effect, methane sets the pace in the near term. At least 25% of today’s warming is thought to be led by anthropogenic methane production.
Now, a study report published in the journal, Philosophical Transactions of the Royal Society A, has evidence to suggest that the majority of the methane gas emitted from the Amazon comes from tree roots. The researchers state that most of the trees responsible for the release of methane are situated on the floodplains of the Amazon basin.
Typically, in the absence of trees, methane is absorbed into the soil in wetland areas along the basin. However, where the wetlands meet the forest areas, the researchers suggest the root systems of the trees carry the methane up through the trunk and vent it out into the atmosphere.
The presence of wetland adapted trees as an important egress pathway presents a more pronounced vertical dimension to previously examined emission pathways both above and below the forest floor. This complicates approaches to quantifying emissions, but yields opportunities to consider new processes of CH4 source access, entrainment and evasion.
Professor Vincent Gauci, the School of Geography, Earth and Environmental Sciences, the University of Birmingham
Underestimating the Extent of Methane Release
If accurate, this means that existing models of methane emissions in the Amazon basin and other wetland areas could be considerably underestimating the extent of the release of the greenhouse gas into the atmosphere.
Since pre-industrial times, methane release has accounted for around 30 percent of global warming and is growing at a fast rate.
In fact, data from the United States National Oceanic and Atmospheric Administration (NOAA), indicates that even as carbon dioxide emissions reduced during the pandemic-related lockdowns of 2020/21, atmospheric methane shot up.
However, while the rate of increase is often attributed to human activities and the ongoing modernization of the industrial world, it is difficult to determine which specific sources are responsible for variations and increases in methane emissions.
In fact, NOAA researchers have previously thought that one of the main drivers of the increased methane emissions came from biological sources of methane, including wetlands or livestock, instead of thermogenic sources like oil and gas production and use.
New Methane Data Models for Climate Change
This latest research from Gauci and his colleagues could prove what others have been suspecting and would be useful for adjusting existing climate models for methane emissions. To further assess their theory, the researchers performed measurements across three different floodplains on three major rivers in the central Amazon basin.
Over the course of a year, the trees were observed at each plot at four time points to harness their response to fluctuating water levels associated with the yearly flood.
Using a portable greenhouse gas analyzer, the methane emissions were then recorded and calculations were made to scale up the findings across the entire Amazon basin.
It was found that trees vent around 50% of global wetland methane emissions during both the dry and wet seasons. This demonstrates that current estimates of global emissions could be missing crucial data and that models should be developed and adjusted to consider the role trees and tree roots systems play in the release of wetland methane emissions.
In doing so, this would give scientists, researchers and policymakers the data needed to accurately assess the need to drive down anthropogenic emission sources and make suitable adjustments to industrial processes and maintain key climate targets in the near future.
References and Further Reading
Gauci, V. and Figueiredo, V., et al., (2021) Non-flooded riparian Amazon trees are a regionally significant methane source. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, [online] 380(2215). Available at: https://doi.org/10.1098/rsta.2020.0446
Research.noaa.gov. (2021) Despite pandemic shutdowns, carbon dioxide and methane surged in 2020 - Welcome to NOAA Research. [online] Available at: https://research.noaa.gov/article/ArtMID/587/ArticleID/2742/Despite-pandemic-shutdowns-carbon-dioxide-and-methane-surged-in-2020