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Fossil leaves may reveal climate in last era of dinosaurs

WASHINGTON (AP) — Richard Barclay opens a metal drawer in archives of the Smithsonian Natural History Museum containing fossils that are nearly 100 million years old. Despite their age, these rocks aren’t fragile. The geologist and botanist handles them with casual ease, placing one in his palm for closer examination.

Embedded in the ancient rock is a triangular leaf with rounded upper lobes. This leaf fell off a tree around the time that T-rex and triceratops roamed prehistoric forests, but the plant is instantly recognizable. “You can tell this is ginkgo, it’s a unique shape,” said Barclay. “It hasn’t changed much in many millions of years.”

What’s also special about ginkgo trees is that their fossils often preserve actual plant material, not simply a leaf’s impression. And that thin sheet of organic matter may be key to understanding the ancient climate system — and the possible future of our warming planet.

But Barclay and his team first need to crack the plant’s code to read information contained in the ancient leaf.

“Ginkgo is a pretty unique time capsule,” said Peter Crane, a Yale University paleobotanist. As he wrote in “Ginkgo,” his book on the plant, “It is hard to imagine that these trees, now towering above cars and commuters, grew up with the dinosaurs and have come down to us almost unchanged for 200 million years.”

If a tree fell in an ancient forest, what can it tell scientists today?

“The reason scientists look back in the past is to understand what’s coming in the future,” said Kevin Anchukaitis, a climate researcher at the University of Arizona. “We want to understand how the planet has responded in the past to large-scale changes in climate — how ecosystems changed, how ocean chemistry and sea levels changed, how forests worked.”

Of particular interest to scientists are “ hothouse ” periods when they believe carbon levels and temperatures were significantly higher than today. One such time occurred during the late Cretaceous period (66 million to 100 million years ago), the last era of the dinosaurs before a meteor slammed into Earth and most species went extinct.

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Friday, August 27, 2021