Washington (AFP) — Richard Barclay opens a metal drawer in the archives of the Smithsonian Museum of Natural History containing fossils nearly 100 million years old. Despite its age, these rocks are not brittle. The geologist and botanist deal with them easily, and puts one in the palm of his hand to examine it more closely.
An integral part of the ancient rock is a triangular leaf with rounded upper lobes. This leaf fell from a tree at the time when T-rex and triceratops were roaming prehistoric forests, but the plant is instantly recognizable. «You can tell this is ginkgo, it’s a unique form,» Barclay said. «It hasn’t changed much in millions of years.»
What also distinguishes ginkgo trees is that their fossils often preserve the actual plant material, not just the impression of the leaf. And that thin layer 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 decode the plant 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 on plants, «It is hard to imagine that these trees, now towering above cars and passengers, originated with the dinosaurs and came 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 at the past is to understand what will happen in the future,» said Kevin Anchokaitis, 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 have changed, how ocean chemistry and sea levels have changed, and how forests work.»
of particular interest to scholars.” greenhouse “Periods in which they think carbon levels and Temperatures It was much higher than today. One of these times occurred during the late Cretaceous period (66 million to 100 million years ago), the last era of dinosaurs Before the meteorite hits the Earth, most species become extinct.
Learning more about greenhouse climates also gives scientists valuable data to test the accuracy of climate models to predict the future, says Kim Cobb, a climate scientist at Georgia Tech.
But climatic information about the distant past is limited. Air bubbles trapped in ancient ice cores allow scientists to study ancient carbon dioxide levels, but those bubbles are only 800,000 years old.
This is where the Smithsonian’s Ginkgo leaf collection comes in. Down a set of lanes, Barclay jumps through thousands of years — as only possible in the museum — to the 19th century, when the Industrial Revolution began changing the climate.
From the cupboard, he pulls out sheets of paper where 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 roughly matches that of a fossil about 100 million years ago, and of a modern paper that Barclay holds in his hand. But one major difference can be seen using a microscope — how the paper responded to the change in carbon in the air.
Small pores are arranged on the underside of the leaf to absorb carbon dioxide and breathing water, allowing the plant to convert sunlight into energy. When there is a lot of carbon in the air, the plant needs fewer pores to absorb the carbon it needs. When carbon levels drop, the leaves produce more pores to compensate.
Today, scientists know the global average carbon dioxide level Atmosphere is about 410 parts per million — and Barclay knows what makes paper look. Thanks to the Victorian plant leaves, he knows what ginkgo leaves looked like before humans dramatically changed the planet’s atmosphere.
Now he wants to know what pores in the fossilized ginkgo leaves could tell him about the atmosphere 100 million years ago.
But first he needs a code separator, translation paper — a kind of Rosetta Stone to decipher ancient atmospheric handwriting.
That’s why he’s doing an experiment in a forest in Maryland.
One morning earlier this year, Barclay and project assistant Ben Lloyd tended rows of ginkgo trees inside exposed containers of plastic wrap that exposed them to rain, sunlight and the changing seasons. «We grow them this way so the plants go through natural cycles,» Barclay said.
The researchers tuned in to the carbon dioxide pumped into each room, and an electronic monitor outside flashed levels every five seconds.
Some trees grow at current carbon dioxide levels. Others grow at dramatically elevated levels, approaching levels in the distant past, or perhaps in the future.
«We’re looking for analogues — we need something to compare,» Barclay said. If there is a match between the shape of the leaves in the experiment and the shape of the fossil leaves, it will provide the researchers with a rough clue to the ancient atmosphere.
They’re also studying what happens when trees grow in highly charged environments, and they’ve found that more carbon dioxide makes them grow faster.
But Barkley adds, “If plants grow too fast, they are more likely to make mistakes and be more susceptible to damage. … It is like a race car driver who is likely to derail at high speeds.”
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