Plants are getting too much blame for global warming, according to a study by scientists at the University of Ediburgh and the National Center for Atmospheric Research.

The research, published in New Phytologist, suggests that plant leaves account for less than one per cent of the Earth's emissions of methane, considered to be about 25 times more potent than carbon dioxide. The results contrast with a previous scientific study which suggested that plants were responsible for producing large amounts of the greenhouse gas.

"Our results show that plant leaves do give rise to some methane, but only a very small amount – this is a welcome result as it allays fears that forestry and agriculture were contributing unduly to global warming," said Dr Andy McLeod, of the University of Edinburgh's School of GeoSciences.

The findings confirm that trees are a useful way of offsetting greenhouse gas emissions, as their output of small amounts of methane is far outweighed by their capacity to store carbon from the atmosphere in their leaves, wood and bark.

Scientists created artificial leaves made from plant pectin and measured the methane produced when the leaves were exposed to sunlight. They combined their results with satellite data on the leaf coverage of the Earth's surface, ozone in the atmosphere, cloud cover, temperature, and information on sunshine levels to help work out the amount of methane produced by all plants on Earth.

Their results refine previous studies that had indicated that the quantity of methane produced by plants might have been much higher. Future research will examine methane production from parts of plants other than leaves, and the amount of methane given off by different species of plants in different regions of the Earth.

Citation: Bloom et al., 'Global methane emission estimates from ultraviolet irradiation of terrestrial plant foliage', New Phytologist, April 2010; doi:10.1111/j.1469-8137.2010.03259.x