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ShareJune 21, 1999 — Writer: Steve Orlando
Source: David Dilcher, (352) 392-6560, dilcher@flmnh.ufl.edu
GAINESVILLE, Fla. --- A University of Florida professor and a group of Dutch colleagues have found a new way to track the concentration of greenhouse gasses in the atmosphere using leaf fossils, according to an article scheduled to appear today (6/18) in the journal Science.
The new method is considerably more accurate -- not to mention easier and less expensive -- than the more common technique of using ice core samples taken from Antarctica, said David Dilcher, a graduate research professor in paleobotany with the Florida Museum of Natural History at UF.
"Wherever there are swamps where leaves have been deposited in peat, this can be done," Dilcher said.
The method uses what is known as stomatal index and is based on carbon dioxide fluctuations in the Earth's atmosphere. The number of pores, or stomata, produced on the underside of the leaf is directly related to the carbon dioxide concentration in the atmosphere, Dilcher said. More carbon dioxide means fewer stomata and vice versa.
"As CO2 fluctuates, temperature seems to be fluctuating," Dilcher said. "It's a delicate balance the leaf is measuring. The plant senses the amount of CO2 in the atmosphere and adjusts accordingly."
One question that remains unanswered relates to cause and effect: Which comes first, carbon dioxide changes or temperature changes? That leaves the door open on whether global warming during the past 100 years or so is a result of man-made greenhouse gases or part of a larger natural cycle. Still, Dilcher said, "it gives some reason for pause, some concern."
While the Science article deals with a fossil record of just a few hundred years, he said, a record going back as far as 10 million years could be created using the stomatal index method. Dilcher can be reached in his office at (352) 392-6560 or by e-mail at dilcher@flmnh.ufl.edu. Fellow researcher Henk Visscher with Utrecht University in the Netherlands can be reached by telephone at 31.348.472139 or e-mail at h.visscher@boev.biol.ruu.nl.
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