Mike Tidwell comments – That plants emit a diverse number compounds, including a very small amount of hydrocarbons, is well documented. But keep in mind that even if plants were emitting a great deal of methane into the atmosphere, this still would not constitute a source of climate change. All carbon emitted by plants originated from the atmosphere. In the long view, the great majority of carbon held by plants is returned to the atmosphere as they die and decompose. Only deep-earth atoms moved from below ground to the atmosphere are a true addition of greenhouse gases to our atmosphere. There is a tendency to blame other earth processes for climate change, but the reality is that the blame rests squarely on our shoulders. It is we who are moving carbon-based molecules, safely locked up underground, into our atmosphere on a massive scale.
Scientists disprove a recent study that suggests plants emit the potent greenhouse gas methane
A recent study in Nature1 suggested that terrestrial plants may be a global source of the potent greenhouse gas methane, making plants substantial contributors to the annual global methane budget. This controversial finding and the resulting commotion triggered a consortium2 of Dutch scientists to re-examine this in an independent study. Reporting in New Phytologist, Tom Dueck and colleagues present their results and conclude that methane emissions from plants are negligible and do not contribute to global climate change.
The consortium brings together a unique combination of expertise and facilities enabling the design and execution of a novel experiment. Plants were grown in a facility containing atmospheric carbon dioxide almost exclusively with a heavy form of carbon (13C). This makes the carbon released from the plants relatively easy to detect. Thus, if plants are able to emit methane, it will contain the heavy carbon isotope and can be detected against the background of lighter carbon molecules in the air.
Six plant species were grown in a 13C-carbon dioxide atmosphere, saturating the plants with heavy carbon. 13C-Methane emission was measured under controlled, but natural conditions with a photo-acoustic laser technique. This technique is so sensitive that the scientists are able to measure the carbon dioxide in the breath of small insects like ants. Even with this state-of-the-art technique, the measured emission rates were so close to the detection limit that they did not statistically differ from zero. To our knowledge this is the first independent test which has been published since the controversy last year.
Conscious of the fact that a small amount of plant material might only result in small amounts of methane, the researchers sampled the ‘heavy’ methane in the air in which a large amount of plants were growing. Again, the measured methane emissions were neglible. Thus these plant specialists conclude that there is no reason to reassess the mitigation potential of plants. The researchers stress that questions still remain and that the gap in the global methane budget needs to be properly addressed.
1’Methane emissons from terrestrial plants under aerobic conditions’ by Keppler F, Hamilton JTG, Braβ M, Rockmann T. Nature 439: 187–191
2The Dutch consortium includes scientists from Plant Research International, IsoLife and Plant Dynamics in Wageningen, Utrecht University, and the Radboud University in Nijmegen.
Notes to Editors
1. The article referred to is available Online Only via Blackwell Synergy:
’No evidence for substantial aerobic methane emission by terrestrial plants: A 13C-labelling approach’ Tom A. Dueck, Ries de Visser, Hendrik Poorter, Stefan Persijn, Antonie Gorissen, Willem de Visser, Ad Schapendonk, Jan Verhagen, Jan Snel, Frans J. M. Harren, Anthony K. Y. Ngai, Francel Verstappen, Harro Bouwmeester, Laurentius A. C. J. Voesenek and Adrie van der Werf
New Phytologist. Article published online: 27-April-2007.
2. For further information, please contact Lucy Mansfield, email: email@example.com or telephone: +44 (0) 1865 476241
3. New Phytologist is an international journal offering rapid publication of high quality original research in plant science. Owned by a not-for-profit organisation, the New Phytologist Trust is dedicated to the promotion of plant science.