Plants Contribute to Global Warming?

If anyone needs a reminder that scientists still have a lot to learn, consider this major discovery of something right under their noses that caught them completely off guard.  Up to a third of methane in the atmosphere comes from plants.  This is not only a baffling puzzle about how or why plants would create such a reducing molecule in an oxic environment, but the finding will have a major impact on how scientists calculate the greenhouse-gas budget – a data point that feeds right into political negotiations over what to do about global warming.  It will also ripple back through models of earth history and climate.  (After carbon dioxide, methane is the major greenhouse gas in the atmosphere; previously, scientists thought most of it was coming from microbial activity in wetlands or cow farts – in scientific terms, the “eructations of ruminant animals.”)
    The astonishment of two news reports in Nature was palpable.  Atmospheric expert David C. Lowe¹ called this startling, because it is the first case of non-bacterial agents producing methane, and the amount is large: up to 30% of the annual total of methane entering earth’s atmosphere.  Methane has been a target for emission control under the Kyoto protocols, but is it possible that by planting forests in some wetland countries will make the problem worse?  They had recommended drier rice farming than flooding rice paddies with water.  Lowe asks, “could the rice plants themselves be as significant a source of methane as the flooded paddy fields?”
    Quirin Schiermeier in Munich was similarly stunned.²  This finding will send scientists and politicians back to the drawing board, he said: “The newly revealed methane emissions have taken plant physiologists by surprise, because far more energy is required to create methane than, say, carbon dioxide in an oxygenated environment.”  A sidebar asked, “How could we have missed this?” and has them “wondering what else might have been overlooked if it is true.”  It could be very important, and may not be the last surprise.  It does not change the fact that atmospheric methane has doubled over the past 200 years, and does not remove the need to understand the human impact on atmospheric change, but “It means we neglected a big driving force for the climate,” remarked Martin Heimann, director of the Max Planck Institute for Biogeochemistry in Jena, Germany, who was most surprised by the large amount of methane detected.
    The discovery was made by Keppler et al. and announced in Nature.³  They said, “We suggest that this newly identified source may have important implications for the global methane budget and may call for a reconsideration of the role of natural methane sources in past climate change.”  See also the summary on EurekAlert.
Update 01/19/2006: The authors issued a clarification in a Max Planck Society press release that their findings were not intended to suggest that plants cause global warming, or that reforestation efforts would be harmful.  “Emissions from plants thus contribute to the natural greenhouse effect and not to the recent temperature increase known as ‘global warming,’ they said.  “Even if land use practices have altered plant methane emissions, which we did not demonstrate, this would also count as an anthropogenic source, and the plants themselves cannot be deemed responsible.”  The authors were apparently chagrined over widespread “misinterpretation” of their findings in the news media; “The blame is not with the plants,” the press release was titled.
Update: see 08/28/2006 headline.

¹David C. Lowe, “Global change: A green source of surprise,” Nature 439, 148-149 (12 January 2006) | doi:10.1038/439148a.
²Quirin Schiermeier, “Methane finding baffles scientists,” Nature http://www.nature.com/nature/journal/v439/n7073/full/439128a.html.
³Keppler et al., “Methane emissions from terrestrial plants under aerobic conditions,” Nature 439, 187-191 (12 January 2006) | doi:10.1038/nature04420.

CEH does not generally take positions on political issues like global warming, but two lessons stand out from this surprising discovery:
(1) Plants must have some yet-to-be-discovered remarkable mechanism for producing an unlikely molecule in oxidizing conditions.  Here’s a chance for an ID-friendly researcher to find out how and why plants accomplish this feat.  Think of the possibilities for ID science: can plants teach us an efficient way to produce natural gas?  Could this bring our energy bills down?
(2) There may be a lot more going on in this old world than the experts, who influence the politicians, could ever realize.  When they speak glibly about what the climate was doing umpteen gazillion years ago, take note of this startling finding that was right under their noses, right here in the present.