Earthwatch Radio on 5 July 2006 highlighted research that was reported in Proceedings of the National Academy of Sciences.
Researchers at Duke University have studied the effects of increasing atmospheric carbon dioxide on a plot of southeastern forest. All of the plants showed a significant increase in growth and biomass, but poison ivy stood out in its remarkable ability to take advantage of the increased CO2.
Quoting William Schlesinger, an environmental chemist at Duke University:
"The poison ivy, as it turned out, not only was it growing faster and accumulating more plant tissue, but it had higher concentrations of the allergenic compound in its leaves. This is the compound that essentially, when you rub it on your skin, produces the skin rash and allergy. So we can look to poison ivy as being bigger as a plant and more toxic in future environments of high carbon dioxide."
Read more at Earthwatch Radio or download the full article at PNAS [free open-access article].