Scientists find trees and plants release methane

According to an article in Nature (12 January) researchers from the Max Planck Institute for Nuclear Physics have made the surprising discovery that plants release methane, a greenhouse gas - and this goes against all previous assumptions.

Equally surprising was that methane formation is not hindered by the presence of oxygen. This discovery is important not just for plant researchers but also for understanding the connection between global warming and increased greenhouse gas production.

Methane is the greenhouse gas, which has the second greatest effect on climate, after carbon dioxide. The concentration of methane in the atmosphere has almost tripled in the last 150 years. Methane is best known as natural gas, currently an important energy source.

Nonetheless, only part of the methane uptake in the atmosphere is due to industrial activities connected to energy production and use. More important for the increase of methane in the atmosphere is the increase in so-called "biogenic" sources, e.g., rice cultivation or domestic ruminants related to the rise in the world's population. Nowadays, methane in the atmosphere in fact is largely of biogenic origin.

The researchers made the surprising discovery during an investigation of which gases are emitted by dead and fresh leaves. Then, in the laboratory and in the wild, the scientists looked at the release of gases from living plants like maize and ryegrass . In this investigation, it turned out that living plants let out some 10 to 1000 times more methane than dead plant material. The researchers then were able to show that the rate of methane production grew drastically when the plants were exposed to the sun.

Although the scientists have some first indications, it is still unclear what processes are responsible for the formation of methane in plants. The researchers from Heidelberg assume that there is an unknown, hidden reaction mechanism, which current knowledge about plants cannot explain - in other words, a new area of research for biochemistry and plant physiology.

The scientists now will continue laboratory work, as well as field and remote sensing studies, to better quantify the strength of these methane emissions. A related exciting question is which role the biosphere has played in methane production in the history of the earth, and what kind of influence rising global temperatures and carbon dioxide concentration have on the production of methane from plants.

Answers to these questions are important for understanding the feedback mechanisms between climate change and greenhouse gas production.

[Original work: Frank Keppler, John T. G. Hamilton, Marc Brass and Thomas Röckmann
Methane emissions from terrestrial plants under aerobic conditions.]

Photo caption: A tropical rainforest in Suriname. Tropical regions are particularly large contributors to the atmosphere's methane budget, according to the latest research from the Max Planck Institute for Nuclear Physics.

Image: Max Planck Institute for Nuclear Physics/B. Scheeren