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Published online 20 August 2008 | Nature | doi:10.1038/news.2008.1053
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Tibetan meadows emit methane
Field survey confirms that plants can boost levels of the greenhouse gas.
A three-year field study on the Tibetan plateau has shown that plant species differ in their ability to emit or consume methane, a potent greenhouse gas. This could shed fresh light on the role of plants in global methane budgets.
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Before we declare all-out war on organisms that produce the 'green-house' gas, methane, and destroy the beautiful Tibetan meadows shown in the photograph above, we need to consider their benefits to humankind. Recent advances in the identification and characterization of the human microbiota have shown that methanogenic Archaea may play a critical role in the maintenance of colonic health and the prevention of cancer (O'Keefe SJ. Nutrition and colonic health: the critical role of the microbiota. Curr Opin Gastroenterol. 2008 Jan;24(1):51-). Fermentation of food residues, such as fibre and resistant starch, by the colonic microbiota produces the short chain fatty acid butyrate which is not only the preferred fuel for the colonic epithelium but also regulates its rate of proliferation, and therefore cancer risk. In the anerobic conditions of the colon, the end-metabolite of the fermentation process is hydrogen which, in excess, is cytotoxic. Consequently, high fermenters such as most peoples living in the 'developing' world harbour large populations of microbes that consume hydrogen to produce methane, a gas that is harmless to the epithelium, is absorbed, and then excreted in breath. Not surprisingly therefore, it has been well documented that populations with high rates of methanogenesis, such as rural Africans, have low rates of colonic diseases and cancer, whilst communities that have low rates of methanogenesis, such as African Americans, suffer from high rates of colon cancer. Further studies need to be conducted to identify how, on balance, the green plants of the meadow shown above benefit nature.