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An aerial view of the two CO•-gradient tunnels.

Details: feature article in Agricultural Research magazine.

Time Tunnel Points to Future in High CO2 World

By Don Comis
December 27, 1999

Higher carbon dioxide levels in the atmosphere may be partly responsible for a worldwide increase in the displacement of grasslands by mesquite and other brushy weeds.

The rise in CO2 levels matches this increase in brush--and the progress of the Industrial Age.

That observation led U.S. Department of Agriculture scientists to build a "time tunnel" three years ago. It's actually two plastic-walled tunnels, with rangeland plants growing inside them. One tunnel goes from today's CO2 level of 350 parts per million to 2050's predicted 550 ppm. The second tunnel goes from the Ice Age level of 200 ppm to today's level.

A tunnel study last year showed that higher CO2 levels caused plants to grow faster and use water more efficiently. This suggests that higher CO2 levels might be speeding brush invasions by allowing plants like mesquite to thrive on less water.

Ecologists H.Wayne Polley and Hyrum B. Johnson, with USDA's Agricultural Research Service at the Grassland Soil and Water Research Laboratory at Temple, Tex., did the study with colleagues at ARS and the Texas Agricultural Experiment Station at Temple. ARS is the chief scientific arm of the U.S. Department of Agriculture.

The time tunnel research is described in a special feature on the future of ARS natural resources research in the current millennium edition of ARS' Agricultural Research magazine. Click here to view the time-tunnel story on the web.

Scientific contact: H. Wayne Polley, ARS Grassland Soil and Water Research Laboratory, Temple, Tex., phone (254) 770-6629, fax (254) 770-6561,

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