Xmas Trees Absorb 'Super' Greenhouse Gas

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Your Christmas tree and its brethren are absorbing methane, a super greenhouse gas that they were previously suspected of emitting. In fact, previous studies put the global methane output by plants at between 62 and 236 teragrams each year. That’s not small potatoes (if you will pardon the vegetable pun), but 10 to 30 percent of all methane entering the atmosphere.

I refer to methane as a “super” greenhouse gas because it does what carbon dioxide does, but packs about 25 times the punch, which is bad. However, methane does not last very as long in Earth’s atmosphere, which is good. Then again, one of the things methane degrades into is carbon dioxide. Bad again. Ugh.

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The discovery that some trees are absorbing methane comes from Elin Sundqvist and colleagues at Lund University and Stockholm University in Sweden. They did some very number-heavy forest and laboratory measurements and analysis of the gases being exchanged by tree branches of pine, spruce and birch trees under a variety of conditions.

“In contrast to earlier studies of CH4 (methane) exchange by plants, we find a net consumption by all plants studied both in situ and in the laboratory,” they conclude in the latest issue of Geophysical Research Letters.

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The discovery could offer a new explanation to an observed leveling off of methane concentrations in Earth’s atmosphere, the researchers say. Earlier work they cite suggested that the methane levels were slowing as a result of less fossil fuel burning (huh?). Another bit of research suggested that maybe there were fewer microbes making methane in the Northern hemisphere.

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“Our results offer a third explanation: that an increasing amount of CH4 has been taken up by vegetation during the last decades as a consequence of increased greenness.”

In other words, the observed increases in vegetation (greening) could mean trees are working harder at absorbing methane. It’s a little bit of good news. It does not mean trees will counteract all the carbon emissions humans are creating or reverse climate change that is now underway. Still, it’s one of the very, very few negative-feedbacks in an otherwise vicious cycle of warming that we see on Earth today.

Images: U.S. National Christmas Tree, 2012 (Image courtesy of the Architect of the Capitol).

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