In 2006, Frank Keppler and his colleagues at the Max Planck Institute in Germany reported that they had found significant CH4 emissions from both dead and living plant material (Keppler et al., 2006). This was a completely unknown source of CH4 and therefore cast some doubt on the net climate forcing impact of the world's forests. Research is still underway into exactly how this CH4 is produced in plants and how significant a source it is globally. Keppler et al. estimated that CH4 emissions from this source could represent 10-30% of global CH4 emissions (62-236 Tg CH4/year for living plants, and 1-7 Tg CH4/year from plant litter). If so, the benefits of terrestrial vegetation as sinks for CO2 may be somewhat offset by the emissions of CH4.
There is need for research to establish the mechanism by which such plant-derived CH4 might be formed, the significance of this new source of CH4 on a global scale and consequently its impact on the net climate forcing effect of terrestrial vegetation.
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