Gingko Leaves Teach Scientists About Climate During Dinosaurs Days
2021-08-30
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1As scientists try to understand the future of our warming planet, critical information may be found in the past.
2At the Smithsonian Natural History Museum, Richard Barclay opens a metal drawer.
3Inside are fossils that are nearly 100 million years old.
4The scientist holds a rock, and inside the rock is an ancient leaf.
5He easily recognizes the plant.
6"You can tell this is ginkgo. It (is) a unique shape," he said.
7"It has (not) changed much in many millions of years."
8Barclay told a writer for the Associated Press that the leaf fell off a tree when Tyrannosaurus rex and triceratops walked through prehistoric forests.
9Ginkgo trees are that old. Gingko leaves are special for another reason.
10Their fossils often contain actual plant material and not simply a leaf's shape.
11So, they may help scientists understand ancient climate systems and as a result the possible future of our warming planet.
12Of special interest to scientists are something called "hothouse" periods.
13These are periods of time when they believe carbon levels and temperatures were much higher than they are today.
14One such hothouse time took place during the late Cretaceous period, which was about 66 million to 100 million years ago.
15This was the last period of dinosaurs -- before a meteor hit the Earth and most animals died out.
16Learning more about ancient hothouse climates can give scientists valuable information to test models that predict future climates.
17But climate information about the distant past is limited.
18Air trapped in ancient ice permits scientists to study carbon dioxide levels.
19But those samples only go back about 800,000 years.
20That is why the Smithsonian's ginkgo leaves are so important.
21For example, the collection contains a leaf from 1896.
22That is around the time when the Industrial Revolution started changing the climate.
23This leaf has the same shape of the 100-million-year-old leaf.
24However, one big difference can be seen with a microscope - how the leaf has reacted to changing carbon in the air.
25The AP story explains that on a leaf's underside are very small holes or pores.
26They are designed to take in carbon dioxide and respire water.
27This lets the plant turn sunlight into energy.
28When there is a lot of carbon in the air, the plant needs fewer pores to take in the carbon it needs.
29When carbon levels drop, the leaf produces more pores.
30Today, scientists know that the worldwide average level of carbon dioxide in the atmosphere is about 410 parts per million.
31And Barclay knows what that makes the leaf look like.
32He also knows what ginkgo leaves looked like before humans had greatly changed the planet's atmosphere.
33Now he wants to know what pores in the fossilized ginkgo leaves can tell him about the atmosphere 100 million years ago.
34So, he is running an experiment in a forest in the state of Maryland, near Washington, D.C.
35He and his team are growing ginkgo trees in a way that lets them experience natural weather - rain, sunlight, and the changing of seasons.
36But the team has the ability to change levels of carbon dioxide in the air.
37Some trees are growing at current carbon dioxide levels.
38Others are growing at much higher levels - about the same as levels in the distant past, and maybe similar to levels that will be seen in the future.
39"We need something to compare with," Barclay said.
40If there are similarities between leaves in the experimental forest and the fossil leaves,
41the researchers will have a general guide to the ancient atmosphere.
42I'm Anna Matteo.
1As scientists try to understand the future of our warming planet, critical information may be found in the past. 2At the Smithsonian Natural History Museum, Richard Barclay opens a metal drawer. Inside are fossils that are nearly 100 million years old. The scientist holds a rock, and inside the rock is an ancient leaf. He easily recognizes the plant. 3"You can tell this is ginkgo. It (is) a unique shape," he said. "It has (not) changed much in many millions of years." 4Barclay told a writer for the Associated Press that the leaf fell off a tree when Tyrannosaurus rex and triceratops walked through prehistoric forests. 5Ginkgo trees are that old. Gingko leaves are special for another reason. Their fossils often contain actual plant material and not simply a leaf's shape. So, they may help scientists understand ancient climate systems and as a result the possible future of our warming planet. 6Of special interest to scientists are something called "hothouse" periods. These are periods of time when they believe carbon levels and temperatures were much higher than they are today. 7One such hothouse time took place during the late Cretaceous period, which was about 66 million to 100 million years ago. This was the last period of dinosaurs -- before a meteor hit the Earth and most animals died out. 8Learning more about ancient hothouse climates can give scientists valuable information to test models that predict future climates. But climate information about the distant past is limited. Air trapped in ancient ice permits scientists to study carbon dioxide levels. But those samples only go back about 800,000 years. 9That is why the Smithsonian's ginkgo leaves are so important. For example, the collection contains a leaf from 1896. That is around the time when the Industrial Revolution started changing the climate. 10This leaf has the same shape of the 100-million-year-old leaf. However, one big difference can be seen with a microscope - how the leaf has reacted to changing carbon in the air. 11The AP story explains that on a leaf's underside are very small holes or pores. They are designed to take in carbon dioxide and respire water. This lets the plant turn sunlight into energy. When there is a lot of carbon in the air, the plant needs fewer pores to take in the carbon it needs. When carbon levels drop, the leaf produces more pores. 12Today, scientists know that the worldwide average level of carbon dioxide in the atmosphere is about 410 parts per million. And Barclay knows what that makes the leaf look like. He also knows what ginkgo leaves looked like before humans had greatly changed the planet's atmosphere. 13Now he wants to know what pores in the fossilized ginkgo leaves can tell him about the atmosphere 100 million years ago. 14So, he is running an experiment in a forest in the state of Maryland, near Washington, D.C. 15He and his team are growing ginkgo trees in a way that lets them experience natural weather - rain, sunlight, and the changing of seasons. But the team has the ability to change levels of carbon dioxide in the air. 16Some trees are growing at current carbon dioxide levels. Others are growing at much higher levels - about the same as levels in the distant past, and maybe similar to levels that will be seen in the future. 17"We need something to compare with," Barclay said. If there are similarities between leaves in the experimental forest and the fossil leaves, the researchers will have a general guide to the ancient atmosphere. 18I'm Anna Matteo. 19Christina Larson reported this story for the Associated Press. Anna Matteo adapted it for VOA Learning English. Ashley Thompson was the editor. 20_________________________________________________ 21Words in This Story 22unique - adj. used to say that something or someone is unlike anything or anyone else : very special or unusual : belonging to or connected with only one particular thing, place, or person 23carbon - n. a chemical element that forms diamonds and coal and that is found in petroleum and in all living plants and animals 24sample - n. a small amount of something that gives you information about the thing it was taken from 25respire - v. of a cell or tissue : to take up oxygen and produce carbon dioxide through oxidation 26compensate - v. to provide something good as a balance against something bad or undesirable