Azara Blog: Ordinary plants found to produce methane in the laboratory

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Date published: 2006/01/12

The BBC says:

Scientists in Germany have discovered that ordinary plants produce significant amounts of methane, a powerful greenhouse gas which helps trap the sun's energy in the atmosphere.

The findings, reported in the journal Nature, have been described as "startling", and may force a rethink of the role played by forests in holding back the pace of global warming.

And the BBC News Website has learned that the research, based on observations in the laboratory, appears to be corroborated by unpublished observations of methane levels in the Brazilian Amazon.

Until now, it had been thought that natural sources of methane were mainly limited to environments where bacteria acted on vegetation in conditions of low oxygen levels, such as in swamps and rice paddies.

But a team led by Frank Keppler of the Max Planck Institute in Heidelberg, Germany, stumbled upon this new effect when studying emissions from the leaves of trees and grasses in conditions similar to those they would encounter in the open air.

To their amazement, the scientists found that all the textbooks written on the biochemistry of plants had apparently overlooked the fact that methane is produced by a range of plants even when there is plenty of oxygen.

The amount of the gas produced increased when the air was warmer, and when there was more sunlight. The paper estimates that this unexplained phenomenon could account for 10-30% of the world's methane emissions.

The possible implications are set out in Nature by David Lowe of New Zealand's National Institute of Water and Atmospheric Research, who writes: "We now have the spectre that new forests might increase greenhouse warming through methane emissions rather than decrease it by sequestering carbon dioxide."

If this turned out to be true, it would have major implications for the rules of the Kyoto Protocol on climate change, which allows countries and companies to offset emissions from the burning of fossil fuels like coal and oil by funding the planting of new forests or the restoration of deforested areas.

But some experts on climate change science and policy say it is far too early to come to this kind of conclusion.

Dr Halldor Thorgeirsson, deputy executive secretary to the UN Climate Change Secretariat, told the BBC News Website that while the study was interesting, the overall impact of this newly discovered source of methane was still speculative.

"We need to look at this, but this study does not for example look at measurements of direct methane emissions from forests, and that is what is needed to get a better handle on what forests do for the climate," said Dr Thorgeirsson.

He added that the system of calculating forestry "credits" under the Kyoto protocol allowed for updated scientific findings to be included in the assessment of the climate benefit of any particular project.

Obviously extremely interesting work, but it is way too early to say that this is definitive. Laboratory conditions are not the same as real world conditions. Presumably plant biochemists will soon enough figure out what the mechanism is, and understanding that will be when the real conclusions can start to be drawn. It is not very plausible that destroying forests is going to be shown to be good for the environment.

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