Along the Atlantic coast of the United States, climate-driven sea level rise is sending salt water increasingly farther inland. The encroaching brine is killing off coastal woodlands in places like North Carolina, leaving behind “ghost forests” of lifeless trees.
Now, a new study suggests these expanding, ghoulish ecosystems are also contributing to climate change via a much less spooky-sounding phenomenon: “tree farts,” reports Valerie Yurk for E&E News.
When these dead trees—or snags as researchers call them—break wind, they release greenhouse gases, including carbon dioxide, methane and nitrous oxide, according to the paper published last week in the journal Biogeochemistry. While tree farts still pale in comparison to emissions from soil, they increased the total emissions of the ecosystem by around 25 percent, according to a statement.
The researchers say quantifying the carbon emissions of these ghost forests will become even more important in the future as sea level rise drowns more trees.
“The emergence of ghost forests is one of the biggest changes happening in response to sea level rise,” Keryn Gedan, a coastal ecologist at George Washington University who was not involved in the study, tells Maria Temming of Science News. “As forests convert to wetlands, we expect over long timescales that’s going to represent a substantial carbon sink,” says Gedan.
That’s because wetlands tend to store more carbon than forests, but until that conversion is complete, the dead trees will “be a major greenhouse gas source,” Gedan tells Science News. Ghost forests are no longer absorbing carbon dioxide to power new growth. As their wood rots, the carbon they once stored is released back into the atmosphere.
For the study, researchers measured the amount of carbon dioxide, methane and nitrous oxide emitted by dead pine and bald cypress trees in five ghost forests of the Albemarle-Pamlico Peninsula in North Carolina over two summers. The team also used the same technique to quantify the greenhouse gas emissions of the soil in each of the poisoned forests.
Overall, the soil emitted four-times the greenhouse gases of standing dead trees, and the snags contributed about a fifth of the ecosystem’s total emissions, per Science News.
"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," says Melinda Martinez, an environmental scientist from North Carolina State and the study’s lead author, in the statement. "Even the smallest fart counts."
Martinez tells Science News that even though emissions from ghost forests may be small compared to transportation or livestock, that it remains important to account for them as scientists try to hone their estimates of global greenhouse gas emissions and predict the course of climate change.