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Climate change's impact on forests being measured via expanding tree trunks

"There's never a boring moment around here," Morrow said. "Even though it sounds like it."

They also had tree jokes. That tree is a poplar. The ones next to it are un-poplar (say it aloud). That's a beech tree. The one next to it?

A son-of-a-beech.

Last year, when Parker analyzed the mountain of data his team had collected, he found something surprising: Their trees were adding bulk at a surprisingly fast rate.

Parker said the best explanations for this all seemed to relate to climate change. Temperatures in the area have risen by three-tenths of a degree; the growing season has lengthened by 7.8 days; and the amount of carbon dioxide in the atmosphere has risen. All of those might speed up photosynthesis, the engine of tree growth.

Which sounds, at first, like a good thing. It would appear that trees were helping more than expected to reduce the world's greenhouse gases, sucking carbon dioxide out of the atmosphere and using it to make leaves and branches.

"The danger of that, of course, is that this can't go on forever," said Kenneth Feeley, a professor at Florida International University. He meant that, even if there was enough carbon dioxide to support more fast growth, the trees would eventually run out of water or plant food. Their growth would slow down, and they would stop absorbing so much carbon.

Other researchers, such as Feeley, say it wouldn't have been possible to notice this trend in the mid-Atlantic if Parker and his crew had not measured so many trees over so much time.

Looking back, Parker said, it was worth putting up with the tree-hugger jokes.

"It's kind of a soothing thing, you know, hugging lots of these," he said, standing next to a poplar he'd just measured. "You can't get too angry if you do a lot of that."

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