Pumping carbon dioxide through pipes into a North Carolina pine forest, Mohan found that poison ivy grew at 2 1/2 times its normal rate, an increase five times the average gain for trees. The noxious vine grew thicker, used water more efficiently and became far more allergenic to humans.

"Poison ivy is fascinating, with its medical implications. But what's really important scientifically is these woody vines have been increasing in abundance all over the planet [and] inhibiting the growth and regeneration of the forest," said Mohan, who released her findings last month.

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