Scientists from the Max Planck Institute (Germany) have made an unexpected sensational discovery: plants-"lungs of the planet"-are responsible for global warming, as they eject methane (CH₄) in great volumes. The content of this gas in the atmosphere increased almost three-fold in comparison with the pre-industrial period. This increase is due to two reasons: technogenic (combustion of organic substances, extraction of mineral fuel) and, as has recently been revealed, biological.

However, it was known previously that one of the groups of organisms "produced" methane: ancient archaebacteria. They live in the depth of marshes* (hence the name "marsh gas"), in the animal intestine, in sediments on the bottom of oceans, lakes, ponds, and flooded rice plantations, in the depths of city dumps and in the Earth's crust, in cracks and cavities of rocks (down to the depth of 8 - 10 km)**. Archaebacteria consume a mixture of carbon dioxide and hydrogen. All these sources eject about 600 mn tons of methane into the atmosphere annually.

In 2005, high content of CH₄ was registered by specialists in tropical regions over the evergreen forests. During the period of observation (August-November) 30 - 40 mn tons were ejected from there into the atmosphere in addition to the above-mentioned volume of the "marsh gas". The German specialists wondered about the source of gas in these regions. They found out that gas was synthesized by plants without participation of bacteria, and the methanogenesis process differed radically from archaebacterial one.

One more important aspect: photosynthesis of plants in forests and savannas differs greatly, and, as was found out, the volume of methane produced by these plants is also different.

After measuring the intensity of this process in many plants from different climatic zones, the natural scientists estimated the total content of methane ejected by all biological organisms of the planet. According to the first, just tentative estimations, live plants produce from 60 to 240 mn tons gas annually (we should like to emphasize that the main contribution is made by tropical forests and savannas); 0.5 to 7 mn tons are produced by dead leaves. All this is responsible for 10 - 30 percent of total annual release of CH₄ into the atmosphere, including technogenic sources. However, Lev Fyodorov, Dr. Sc. (Chem.), the President of Union "For Chemical Safety", sees nothing frightful about it. "The global warming," he asserts, "is an invention needed for solution of economic problems. If formerly speculations about the role of carbon dioxide and carbon monoxide were popular, now methane is much spoken about. But actually there is no warming or cooling; there are great climatic cycles in nature, which people hope to change. I would not discuss this problem with biologists, as they missed methane ejection, if it really had taken place."

However, not all specialists are so categorical. "Our natural scientists came to similar conclusions, but the topic aroused no active discussion," emphasized Maria Sine-tova (staff member of the RAS Institute of Plant Physiology). "There is nothing frightful about it, the volume of ejected methane did not increase because of a 'sensational' discovery. We have just learned that in addition to methanogens, some representatives of the flora also do the same. By the way, it has recently become known that the main sources of oxygen on our planet are not plants, but very small cyanobacteria in the ocean, which we should take care of and not contaminate, if we want to survive."

Serova Ye., Moskovskaya pravda, March 6, 2006.

Prepared by Yaroslav SIBIRTSEV.

* See: "Marsh Gas". Science in Russia, No. 1, 2006. -Ed.

** See: A. Ruban, V. Zaburdyaev, "Coal Mine Methane", Science in Russia, No. 3, 2006. -Ed.