Carbon Dioxide Kept In Check | July 6, 2009 Issue - Vol. 87 Issue 27 | Chemical & Engineering News
Volume 87 Issue 27 | p. 25 | Concentrates
Issue Date: July 6, 2009

Carbon Dioxide Kept In Check

Land plants' impact on atmospheric CO2 cycling appears to have prevented CO2 levels from dropping too far — and global freezing
Department: Science & Technology
News Channels: Environmental SCENE
Keywords: atmosphere, 2">CO2, plants
Tree roots help accelerate weathering of basalt bedrock in Hawaii.
Credit: Carl Bowser/Silver Pixel Images
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Tree roots help accelerate weathering of basalt bedrock in Hawaii.
Credit: Carl Bowser/Silver Pixel Images

Land plants may have played a vital role in maintaining a consistent concentration of atmospheric CO2 over the past 24 million years, helping to prevent Earth from freezing over, scientists report (Nature 2009, 460, 85). This CO2 stability has been a mystery because of an inherent imbalance of two important geological processes. According to best estimates, the uptake of CO2 during the weathering of silica-based minerals that occurs as mountain ranges grow should have far exceeded the CO2 output from volcanic activity. Without some kind of balancing influence, a “runaway icehouse” effect stemming from declining CO2 levels should have rendered Earth a frozen ball by now. Yale University’s Mark Pagani and colleagues suggest that the decline in plant growth that comes with lower CO2 concentrations curbs the plants’ ability to weather rocks, thereby providing a negative-feedback system to keep CO2 levels from falling too far.

 
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