Greenhouse gas emissions from dead trees in 'ghost forests' are known informally as 'tree farts' - and they are helping to drive climate change.
Ghost forests often form when rising sea levels force salt water into a wooded area, leaving dead and dying trees still standing.
Researchers from North Carolina State University in the US found that standing dead or dying trees in coastal wetland areas release greenhouse gases.
They observed that, while dead and dying trees don't release as much greenhouse gas as soil, they increase emissions from the ecosystem by about 25%.
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Graduate student Melinda Martinez, of North Carolina State University, said: "Even though these standing dead trees are not emitting as much as the soils, they're still emitting something, and they definitely need to be accounted for.
"Even the smallest fart counts."
The researchers measured emissions of carbon dioxide, methane and nitrous oxide from dead pine and bald cypress trees in five ghost forests on the Albemarle-Pamlico Peninsula in North Carolina.
They had been tracking the spread of ghost forests due to sea level rise.
Martinez said: "The transition from forest to marsh from these disturbances is happening quickly, and it’s leaving behind many dead trees. We expect these ghost forests will continue to expand as the climate changes."
Using portable gas analysers, the researchers measured gases emitted by dead trees and from soils in each forest in 2018 and 2019.
The work lays the foundation for their ongoing work to understand the role dead trees are playing in emissions – whether they prevent emissions, like corks, or release them like straws.
Co-author Marcelo Ardon, associate professor of forestry and environmental sciences at North Carolina State University, said: "We started off this research wondering, 'Are these snags [dead or dying trees] straws or corks? Are they facilitating the release from soils, or are they keeping the gases in?'
"We think that they act as straws, but as a filtered straw. They change those gases, as the gases move through the snags."
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