Poison ivy to flourish as planet warms up

Poison ivy. The stuff is all over the place. All you have to do is brush against the stuff, and the next day you’ve got an itchy rash that lasts for days.

It’s going to get worse.

Jacqueline E. Mohan, an assistant research scientist at the Marine Biological Laboratory in Woods Hole, Mass., can prove it.

She monitored the growth of poison ivy vines growing under today’s atmospheric conditions and under the atmospheric conditions that global warming is expected to produce by midcentury, with elevated carbon dioxide concentrations.

The research was conducted in North Carolina as part of an ambitious Duke University Free-Air CO2 Enrichment experiment, in which rings of PVC pipe were used to suffuse sections of forest with elevated levels of carbon dioxide.

“Poison ivy grew 149 percent faster when it was growing in the elevated rings,” Mohan said. On the other hand, there was little or no difference in the growth of young trees in the same forest.

Not only did the elevated carbon dioxide boost poison ivy growth, but it also increased the most toxic form of urushiol, the plant chemical that causes the rash in humans, Mohan and her colleagues found.

The study findings, published recently in the Proceedings of the National Academy of Sciences, should interest a sizable audience; Mohan noted that a U.S. Forest Service study found that 80 percent to 85 percent of people are susceptible to poison ivy.