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1 .This is Scientific American 60-Second Earth. I'm David Biello.Your minute begins now.
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2 .The red cedar trees of Grant County, West Virginia can tell a fascinating tale.
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3 .Because locked inside them is the history of U.S.air pollution in the 20th century.
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4 .Researchers began pulling cores from five randomly selected red cedar trees in 2008.
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5 .The ratio of heavy and light isotopes of carbon found in the tree rings told them many secrets about the trees and their environment.
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6 .From the 1940s through the 1970s, the trees closed the tiny holes in their leaves known as stomata to protect themselves from acid rain.
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7 .That acid rain was coming from the sulfur dioxide pollution spewed by coal-fired power plants upwind in states like Ohio.
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8 .Then, in 1982 or so, about 10 years after passage of the Clean Air Act that cut back on such pollution, the stomata began to reopen.
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9 .And they've been opening wider ever since, boosting growth.
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10 .The red cedars also show that the same thing happened back in the 1930s,
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11 .because the Great Depression's effect on industry actually helped clean up the air.
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12 .The research appeared in Proceedings of the National Academy of Sciences.
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13 .The question now is: what will the red cedars tell us about increasing levels of CO2 from all our fossil fuel burning a few decades from now?
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14 .Your minute is up, for Scientific American 60-Second Earth. I'm David Biello.
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