Poison Ivy Itchier, More Plentiful With Warming, Study Says

Brian Handwerk
for National Geographic News
May 30, 2006

Global climate change may soon make our planet a much itchier place.

Rising levels of carbon dioxide—a so-called greenhouse gas that traps heat within Earth's atmosphere—can fuel booming poison ivy growth, a new study reports.

Even worse, the rash-inducing vines may become more potent.

Working in a Duke Univerity-owned forest near Chapel Hill, North Carolina, researchers used a system of carbon dioxide-pumping pipes to create atmospheric CO2 levels that were some 200 parts per million higher than the current norm.

Many global warming models predict that such levels will be a reality by 2050. (Related: "Global Warming Could Cause Mass Extinctions by 2050, Study Says" [April 12].)

Poison ivy growth surged some 150 percent in the carbon dioxide-rich forest plots.

Poison ivy afflicts countless people each year—more than 350,000 Americans alone are miserable enough to seek professional treatment.

Found in woody areas across North America, the plant also grows in Central America and parts of Asia, and has been introduced to Europe, Africa, Australia, and New Zealand.

About 80 percent of all people are allergic to poison ivy's sap or resin. Sufferers experience a red, bumpy, itchy, and sometimes blistering skin rash when they come into contact with urushiol—the plant's carbon-based active compound.

Unfortunately, the study also found that carbon dioxide-enhanced poison ivy boasts a stronger strain of urushiol, which may prove even more poisonous to humans.

"That was a bit of a surprise," said lead author Jacqueline Mohan, a postdoctoral scientist at the Ecosystems Center of the Marine Biological Laboratory in Woods Hole, Massachusetts.

"It was not actually producing more of the carbon compounds but producing a more poisonous form."

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