To probe the links between fossil plants and ancient climate change and potentially help scientists gain new insight into climate change today, researchers at The Johns Hopkins University and the University of California-Berkeley turned to the fossil plants' next-of-kin: contemporary plants.

Through a study of data on 176 species of modern-day plants, the authors found evidence that fossil plants can help scientists determine the sources of carbon in the atmosphere hundreds of millions of years ago, a source of useful insight into ancient climates. However, their results, published recently in "Paleobiology," put a potentially more direct link between fossil plants and carbon levels in the prehistoric atmosphere in doubt.

"We have to keep in mind that these ancient organisms operated according to their own ecological agenda," says Hope Jahren, assistant professor of Earth and Planetary Sciences at Johns Hopkins, and an author of the paper. "However, there's still a great deal of meaning therewe just have to look for it from the plant's perspective."

Jahren and the other authors analyzed data from 44 modern plant studies conducted by other scientists. They selected studies of C3 plants, the most prevalent type of plant on Earth now and for the last four hundred million years. C3 plants include all the trees and some grasses.

Scientists found a promising connection between the ratios of carbon isotopes in the air and in the plants. Isotopes are forms of an element that differ only by the addition of one or more subatomic particles known as neutrons. Different isotopes of the same element, identified by a number after the element name, can have different physical properties.

Plants absorb both the isotopes carbon 13 and carbon 12, bound in carbon dioxide, from the atmosphere. As the plant moves carbon from the stomata to sites where it is prepared for use in photosynthe
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Contact: Michael Purdy
mcp@jhu.edu
410-516-7160
Johns Hopkins University
17-Feb-2000