As if widespread drought, mass extinctions, more severe storms, etc. were not sufficient cause for concern, a study by Duke University recently reported that the concentrations of carbon dioxide that lead to climate change also cause poison ivy to become more prolific.  The effect on poison ivy is greater than that on other woody species.  The increased concentrations of carbon dioxide also cause the plant to produce a more allergenic form of urushiol, the chemical that causes the allergic reaction.