The Kind of Misery Itched in Memory

By Lori Aratani
Washington Post Staff Writer
Saturday, August 23, 2008

There are things about summer -- long days, shaved ice, fresh-off-the-tree-peaches -- that we love. And then there are those things we simply tolerate because, well, the pessimist in us says that life can't possibly be that perfect, so we must suffer, just a bit.

Well, it appears we could be suffering a bit more in coming days.

Polar bears might be endangered because global warming is melting their homes on arctic ice shelves, but one species is thriving: poison ivy.

A growing body of research shows that in controlled experiments, poison ivy goes crazy in an atmosphere rich in carbon dioxide. Many plants grow better when they get extra carbon dioxide, but researchers were surprised to learn how well poison ivy did.

"It isn't that other plants can't grow as well, it's just that poison ivy grows so much more," said Lewis H. Ziska, a plant physiologist who specializes in crop systems and global change for the U.S. Department of Agriculture's Agricultural Research Service in Beltsville. One theory is that poison ivy, and vines in general, don't have to invest as much of their carbon (obtained from carbon dioxide) in trunks and branches as trees do.

And that just scratches the surface.

"It's going to be like a one-two punch: more poison ivy and more poisonous poison ivy," said Xianzhong Wang, a professor of biology at Indiana University-Purdue University Indianapolis, who studies the effect of carbon dioxide on plant growth.

Isn't it just our luck that among its leafy green counterparts, poison ivy would be the class overachiever?

This is not what Rachel Caspi wants to hear. She had a run-in with the vine earlier this summer.

"Oh, it was awful," said Caspi, an immunologist at the National Institutes of Health who ran into a cluster of poison ivy along a trail in Rock Creek Park. It was Father's Day, and Caspi was running along the paved path, as she often does, when she brushed against a cluster of green leaves.

"It was unavoidable," the Bethesda resident said, an indignant tone in her voice. "It was right there, right up along the path."

By late that evening, her legs were red and itchy.

"Three weeks," she said. "It took me three weeks to get over it. The rash got infected -- I can send you pictures."

Thank you, but we have our own.

Each year, 350,000 cases of poison ivy occur in the country. According to the U.S. Food and Drug Administration, once contact has occurred, redness and swelling appear in 12 to 48 hours. Blisters and itching follow.

The most well-known poison ivy-global warming study, by Duke University and the USDA, said the "current increase in global atmospheric carbon dioxide concentrations bears consequences for human health on a panoptic scale."

In other words, things could get far worse for the 85 percent of the population that is allergic to urushiol, the sap secreted by poison ivy and its close cousins, poison oak and sumac. (Poison ivy is also related to cashews and mangoes. Some folks who come in contact with a mango's skin get a similar, poison-ivy-like reaction).

"You want to see poison ivy? C'mon over -- I'll show you poison ivy," says Carole Bergmann, a forest ecologist with the Montgomery County parks system.

She wasn't kidding.

She pointed to a few innocent-looking green sprouts mixed in with the grass, not more than 200 feet from the back door of her office at Wheaton Regional Park. Hrrumph. Hardly a threat.

"Now look up," she said.

That's when things got scary. A tangle of poison ivy vines had practically swallowed a tulip poplar tree. If that wasn't enough, a four-inch-thick gray-and-brown rope ran up the tree's trunk. Poison ivy roots. Eww.

Bergmann has not done any controlled studies; she knows only what she sees. And what she sees is poison ivy. A LOT of poison ivy.

"I really do think that vines are growing a heck of a lot more crazily than they were 20 years ago," Bergmann said as she continued the tour. "And this year with all the rain -- well, everything loves the rain. Just walking around, I've seen very healthy colonies of poison ivy."

Bergmann said that although the old "leaves of three, leave it be" warning still applies, it does not apply in all cases. Poison ivy "can be in a small cluster or in upright bush form.''

And it's not always ground-bound.

"It can climb trees,'' she added.

So is it time put the camping gear in storage and check into the nearest hotel? Or should we be rounding up the Roundup?

Eric Burkhart, program director for plant science at Shaver's Creek Environmental Center at Penn State University, is no fan of the vine but said people need to think before they grab their weed whackers.

Poison ivy is a native plant that plays an important role in forest life. Deer, rabbits and 40 species of birds depend on its berries and leaves for food. (And, no, scientists don't think it's possible for deer to be trained to eat only poison ivy, but thanks for asking.)

"People have to recognize that something we find not very useful has value in the world," Burkhart said. "Aside from just the fact there might be a lot of birds and critters that can consume the berries and deer that eat the foliage, these are carbon sinks -- these are actually taking up carbon."

Poison ivy's penchant for thriving in carbon dioxide-rich environments may yield human benefits. Part of Ziska's job at the Agricultural Research Center is to determine whether the qualities that allow poison ivy to thrive can be transferred to such plants as soybeans, wheat and rice.

Ziska said we may just have to learn to live with our itchy nemesis. The best defense?

"At this point, there are two things: awareness and education," he said. "When you do come in contact with it, wash it off as soon as possible."

After being told about poison ivy's more positive contributions, Caspi was only slightly convinced.

"It's a perfectly legitimate plant. The only problem is when it grows in inappropriate places, where people go and children play and dogs sniff," she said. "It's allowed to flourish. It should, as part of the normal upkeep of the trails, be controlled."

Weed whacker, anyone?