Frank Keppler and his team created a storm when they suggested plants were responsible for up a third of the methane entering the atmosphere. This runs contrary to current thinking that only waterlogged vegetation produces the gas. Any change would require a rewrite of climate change models and finally condemn forestry sink projects.
But rival scientists from the Netherlands claim to have disproved Dr Keppler’s theory after carrying out experiments with a radioactive carbon isotope.1Tom Dueck and his fellow researchers tested six plant species - several of which had been used in the original study - but saw only negligible methane emissions.
They think Dr Keppler’s methane may have come from the soil or small spaces in the plants, rather than being produced by the plants.
Dr Keppler rejects this suggestion: "I am still absolutely confident that plants produce methane under aerobic conditions," he says.
"Since the experimental set-up used for the studies was so very different, making comparisons between them is futile."
He admits some researchers are having difficulty repeating his team’s results but says several other studies, as yet unpublished, support his findings.