Washington (AFP) – Richard Barclay opened a metal drawer in the archives of the Smithsonian Museum of Natural History that contain fossils that are nearly 100 million years old. Despite its age, this rock is not brittle. Geologists and botanists handled them with ease, and placed one in the palm of his hand to examine them more closely.
An integral part of the ancient stone is a triangular leaf with a rounded upper lobe. This leaf fell from the tree at a time when T-rex and triceratops roamed the prehistoric forest, but the plant was instantly recognizable. “You can tell it’s ginkgo, it’s unique,” says Barclay. “It hasn’t changed much in millions of years.”
What also sets ginkgo trees apart is that their fossils often preserve the actual plant material, not just the impression of the leaves. And that thin layer of organic matter may be the key to understanding the ancient climate system — and the possible future of our warming planet.
But Barclay and his team first needed to crack the factory code to read the information in the old paper.
“Gingko is a very unique time capsule,” said Peter Crane, a paleontologist at Yale University. As he wrote in his book “Ginkgo” book about plants, “It’s hard to imagine that these trees, now towering over cars and passengers, came from dinosaurs and came down to us almost unchanged for 200 million years.”
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If a tree fell in an ancient forest, what could it say to scientists today?
“The reason scientists look back at the past is to understand what the future holds,” said Kevin Anchokaitis, a climate researcher at the University of Arizona. “We wanted to understand how the planet has responded to large-scale climate change in the past – how ecosystems have changed, how ocean and sea level chemistry has changed, and how forests work.”
interesting to scholars.” greenhouse “The period in which they think about carbon levels and temperature It was much higher than today. One of them occurred during the late Cretaceous period (66 million to 100 million years ago), the last era dinosaur Before the meteorite hit Earth, most species became extinct.
Learning more about greenhouse climates also gives scientists valuable data to test the accuracy of climate models for predicting the future, said Kim Cobb, a climate scientist at Georgia Tech.
But climate information about the distant past is limited. Air bubbles trapped in ancient ice cores allowed scientists to study ancient carbon dioxide levels, but the bubbles are only 800,000 years old.
This is where the Smithsonian’s Ginkgo leaf collection comes in. Down a series of paths, Barclay leaps over thousands of years – which is only possible in a museum – to the 19th century, when the Industrial Revolution began to change the climate.
From the cupboard, he pulled out a sheet of paper on which Victorian scholars recorded and pinned ginkgo leaves plucked from the botanical gardens of their day. Several specimens have beautiful cursive labels, including one dated August 22, 1896.
The shape of the leaf is roughly the same as that of the fossil about 100 million years ago, and the modern paper that Barclay held in his hand. But one major difference can be seen using a microscope – how the paper responds to changes in carbon in the air.
Tiny pores are arranged on the underside of the leaves to absorb carbon dioxide and breathe water, allowing the plant to convert sunlight into energy. When there is a lot of carbon in the air, plants need fewer pores to absorb the carbon they need. When carbon levels drop, leaves produce more pores to compensate.
Today, scientists know the global average carbon dioxide level The atmosphere is about 410 parts per million – and Barclay knows what makes paper visible. Thanks to the leaves of the Victoria plant, he knows what ginkgo leaves looked like before humans changed the planet’s atmosphere dramatically.
Now he wants to know what pores in the fossilized ginkgo leaf could tell him about the atmosphere 100 million years ago.
But first he needed a code separator, translation paper – a kind of Rosetta Stone to decipher ancient atmospheric handwriting.
That’s why he conducted experiments in the woods in Maryland.
One morning earlier this year, Barclay and project assistant Ben Lloyd tended rows of ginkgo trees in open containers of plastic wrap that exposed them to rain, sun, and the changing seasons. “We grow it this way so it goes through a natural cycle,” says Barclay.
The researchers tuned in to the carbon dioxide pumped into each room, and electronic monitors outside emitted levels every five seconds.
Few trees grow at current levels of carbon dioxide. Others are growing at dramatically increasing rates, approaching levels in the distant past, or perhaps in the future.
“We were looking for analogues – we needed something to compare,” said Barclay. If there was a match between the shape of the leaves in the experiment and the shape of the fossil leaves, it would give researchers a rough clue about the ancient atmosphere.
They also studied what happens when trees grow in a highly electrically charged environment, and they found that more carbon dioxide made them grow faster.
But Barkley adds, “If plants grow too fast, they tend to make mistakes and are more prone to damage. … It’s like a race car driver who tends to skid at high speeds.”
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The Associated Press Department of Health and Science receives support from the Howard Hughes Medical Institute’s Division of Science Education. AP is fully responsible for all content.
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