A Chinese soil scientist has warned that rises in global carbon dioxide emission may make grain less nutritious -- the protein level in cereal, for example, may be lowered by 10 percent in the coming four decades.

"With higher density of greenhouse gas, plants will breathe in more carbon dioxide and grow faster -- but not necessarily better," said Zhu Jianguo, a researcher with the Nanjing Institute of Soil Science, a branch of the Chinese Academy of Sciences.

Song's institute teamed up with a Japanese institute of agricultural environmental technologies in 2001 for a joint research program on how higher carbon dioxide density in the coming decades may affect the cropland ecosystem in Wuxi and Jiangdu cities of east China's Jiangsu Province.

The scientists simulated a closed agricultural environment with increasingly higher density of carbon dioxide, and by the time the emission reached the level forecast for 2050, rice in the field had grown 10 to 14 percent faster than normal and wheat, 12 to 20 percent, said Song.

"Higher density of carbon dioxide is like a 'gassy fertilizer' that speeds up their growth, but shortens their growth period, too, by an average six to nine days," said Song, who is chief scientist for the three-year research program. "As a result, the grain becomes less nutritious, with contents of protein, amino acid and trace elements such as iron and zinc all declining."

He said these changes might impact China's soil as well as its grain quality and food security. "With more carbon dioxide inhaled, the rice may appear whiter and taste more glutinous, but you might feel hungry again two or three hours after a full meal because the actual intake of necessary nutritious elements has dropped".

Song welcomed the Kyoto Protocol that came into effect on Feb. 16, noting it marks mankind has finally taken a decisive step forward to safeguarding the planet by curbing global warming.

Experts have warned time and again that the warming climate can cause the sea level rising, glaciers shrinking, desertification accelerating and biological diversity lessening. Livestock husbandry also bears the brunt as certain species, particularly in some alpine and polar regions, could be endangered with extinction.  

(Xinhua News Agency February 23, 2005)