A study led by scientists at Cambridge University and Royal Holloway, University of London, has shown that plants are not guilty of creating tens of millions of tonnes of the potent greenhouse gas methane, despite earlier reports.

It is a relief to know that plants are not guilty.

Dr Ellen Nisbet

The latest study, by Dr Ellen Nisbet and colleagues, reported in the journal Proceedings of the Royal Society B, showed that although plants can take up methane dissolved in water through their roots and emit it through their leaves, they do not make methane themselves under normal conditions.

The study contradicts a report published in 2006 claiming that plants make large quantities of methane themselves. Dr Nisbet's study shows that, although plants can emit methane, it is made by bacteria in the soil and recycled through plant tissues. Plants are therefore not guilty of making huge quantities of this potent greenhouse gas, and the finger is pointed at soil bacteria.

Commenting on the study, Dr Ellen Nisbet, formerly at Cambridge University and now at the University of South Australia, said 'It is a relief to know that plants are not guilty. Forests are immensely precious. Growing plants remove enormous amounts of carbon dioxide from the atmosphere each day through photosynthesis: carbon dioxide that would otherwise be causing global warming'.

Prof Christopher Howe, leader of the Cambridge University team, said 'Although this identifies the source of a natural contribution to greenhouse gases, the imbalance that causes global warming comes from human activities that increase the atmospheric levels of greenhouse gases such as carbon dioxide'.

Prof Euan Nisbet (father of Dr Ellen Nisbet) who leads the group at Royal Holloway, University of London, added that cutting anthropogenic emissions of methane is one of the easiest and cheapest ways to reduce greenhouse warming.

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