Pumped Up on Carbon Dioxide, Vines Strengthen Their Grip

"We're getting more calls from the public," says Mark Smith of Maryland's Agriculture Department, near poison ivy. (By Susan Biddle -- The Washington Post)
By Elizabeth Williamson
Washington Post Staff Writer
Saturday, July 15, 2006

Vines -- poison ivy, Japanese honeysuckle, kudzu -- snake through the back yard, girdling trees and strangling shrubs, thriving, scientists say, on the same pollution they blame for global warming.

From backyard gardens to the Amazon rain forest, vines are growing faster, stronger and, in the case of poison ivy, more poisonous on the heavy doses of carbon dioxide that come from burning such fossil fuels as gasoline and coal.

Complaints about vine infestation have increased tenfold in a decade, said Carole Bergmann, forest ecologist for the Maryland-National Capital Parks and Planning Commission, which serves Montgomery and Prince George's counties. Vines have choked gardens, ruined brickwork, disrupted bird habitat and clogged paths, ponds and air conditioning and electronic equipment.

"The woods they used to know have just changed character," Bergmann said. "They're covered with vines. The trees are being weakened and falling over -- or strangled."

That leaves scientists worried that the forest of the future could become a weedy tangle of hyper-vines choking off the trees, which absorb more carbon dioxide.

As vines become stronger, they also grow more various, a problem researchers say is at least partly attributable to climate change.

"Fifteen years ago, kudzu" -- known as the vine that ate the South -- "would not survive in the D.C. area," Bergmann said, because the climate was too cold. "Now it survives even up in New York."

For six years, Jacqueline Mohan has worked at Duke University to study elevated carbon dioxide levels' effect on woodland life.

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.

"This work suggests that atmospheric carbon dioxide is at least partially responsible."

But the vines also hint at a tantalizing solution to global warming: Perhaps scientists can engineer a plant that would absorb extraordinary amounts of carbon dioxide and clean the air without throwing forests wildly off kilter.

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