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.
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 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."
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