Amazon trees are major source of methane emission

Trees growing in floodplains surrounding the Amazon river emit up to 20 million tonnes of methane gas (CH4) to the atmosphere every year.

Amazon. Image credit: Francisco Chaves/Wikipedia (CC BY 2.0)

Methane is one of the three most potent greenhouse gases and traps up to 34 times more heat compared with carbon dioxide.

The amount calculated in the study is similar to emissions from the Arctic tundra, or emissions from all oceans combined, or the total volume of methane emitted from wild animals and termites globally.

Still, the amount of methane emitted from Amazon trees is just half that emitted by humans, according to the authors — whether in the form of emissions from landfills, the meat industry, or burning fossil fuels.

The researchers argue that although they result from a natural process, these emissions may also be responding to environmental change, such as the building of dams across the Amazon basin. A separate study has reported that 140 hydroelectric dams are in operation or under construction along the Amazon basin, and another 288 are planned for the coming years.

The findings are based on measurements of methane emissions taken from 2,300 trees spread across a number of locations surrounding the rivers Negro, Solimões, Amazonas and Tapajós — where the water level can flood trees by up to 10 metres.

The researchers used gas chambers placed around tree trunks to estimate fluctuations in emissions at a small scale. They also measured methane with an aircraft flying across the entire Amazon basin in order to also calculate emissions at a large scale.

By analysing the measurements collectively, they found that trees growing in wetland areas of the Amazon subject to seasonal flooding emit 21.2 million tonnes of methane gas to the atmosphere every year.

These trees act as chimneys, funnelling the methane produced in the submerged soil into the atmosphere. (SciDev.Net)

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