Greenhouse Effect is a 'Gas' for Virulent Poison Ivy

By Sandy Bauers
Inquirer Staff Writer

Duke researchers confirm what foresters have noticed for years: The greenhouse effect is a gas for the virulent vines.

Never mind that Atlantic City will be underwater and the rest of us blown away by hurricanes. Here's another threat associated with global warming: giant poison ivy vines.

And for those who come in contact with them, a more vigorous version of the horrendously itchy and ugly rash.

For decades, foresters have noted the increased abundance of woody vines. They suspected rising levels of carbon dioxide, which fuels photosynthesis.

Now, researchers who spent six years monitoring plots of poison ivy in the Duke University forest - to their eventual discomfort - have proved it.

Lead researcher Jacqueline E. Mohan was a Duke doctoral student when she picked poison ivy for her study because, as only a scientist might say, it is "a very special type of plant."

Yeah. Anyway...

They went into the woods, selected plants and rigged a circle of PVC pipe with holes in it around each plant.

They blew normal air through some of the pipes and air with elevated levels of carbon dioxide, matching what climatologists predict for the year 2050, through others.

The plants that got the carbon dioxide boost grew nearly 150 percent faster.

Every month during what turned out to be an itchy summer - Mohan learned to wear a triple layer of latex gloves duct-taped to long sleeves - she and her team harvested leaves and analyzed their urushiol, the oil that causes the rash.

Even now, according to her report in the Proceedings of the National Academy of Sciences, the stuff is so nasty that it could be used as a model for chemical-warfare agents.

But it gets worse. The researchers determined that the urushiol hopped up on CO2 was 30 percent more irritating.

"It's making me itch just thinking about it," said Patricia Schrieber, community education manager for the Pennsylvania Horticultural Society. "I'm extremely allergic."

She lives in Chester County, and just last weekend she was taking note of a bankful of poison ivy she has to do something about. "The leaves are huge. Absolutely huge." Maybe eight inches across, she figures.

Perhaps this is a banner year, no matter our carbon dioxide levels, not that anyone has been brave enough to find out.

"It does seem pretty lush this year, pretty widespread," said Kevin Crilley at the Green Lane Nature Center in Montgomery County. Last fall's rain? Spring's cool temperatures? For some reason, "it's just a very successful plant, unfortunately."

Although places such as Scout camps patrol for poison ivy and kill it, most parks leave it alone "unless it's encroaching on a picnic table," Crilley said.

It does have its pluses. Birds eat it. Never mind that they then disperse it in your garden or around your child's swing set.

It's a native plant, one that Steve Atzert, manager at the Shore's Edwin B. Forsythe National Wildlife Refuge, is happier about than the invasives, such as Japanese honeysuckle, stilt grass and knotweed.

"If you've seen it en masse in autumn, it far outshines some of the sugar maples in color," said Dennis Burton, executive director of the Schuylkill Environmental Education Center. "Oh, it's beautiful."

What with the impressive arm-sized hairy vines of the older plants, he wonders whether there's not undiscovered landscape potential for the plant.

He is not, of course, allergic to it, unlike roughly 85 percent of the rest of us, which suggests serious public health implications for the Duke research.

Forest ecologists also worry about poison ivy smothering trees. Because the vines don't have to put energy into supportive plant tissue - the trees they climb on provide that - they can go gangbusters, producing new growth and leaves.

Meanwhile, summer's usual wave of prevention and treatment potions is hitting the shelves, leading annual itchers to wonder why there has been no definitive solution yet.

Among the new products is Tecnu Extreme, a scrub lauded (by its makers) as the "benchmark" for poison ivy rashes.

Its secret weapon is Grindelia robusta, a yellow flower used in homeopathic remedies.

An earlier version was developed by an Oregon chemical engineer to wash off nuclear fallout dust. He hoped it would become a bomb shelter staple.

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