Occasionally, he added, he sees poison ivy growing as shoulder-high shrubs with bigger leaves and stronger urushiol — the toxin present in all parts of the plant. Urushiol causes the blistering, itchy skin rashes in people exposed to poison ivy.
What’s the reason for the teeming lushness among woody vines? Hightower believes it’s because of more carbon dioxide in the atmosphere from fossil fuel burning and other sources.
There’s solid scientific evidence for that. A 2006 Duke University study found that poison ivy exposed to higher atmospheric levels of CO2 grows faster and larger, and the urushiol in them becomes more allergenic. The study was led by ecologist Jacqueline Mohan, now at the University of Georgia.
Other woody vines appear similarly affected, although trees don’t seem to benefit as much.
A saving grace is that native vines play important ecological roles. For instance, poison ivy’s enormous system of roots and rhizomes helps prevent soil erosion; in the fall, its berries — though toxic to humans — provide sustenance to birds and some mammals.
Ecologists, however, worry that a proliferation of woody vines eventually may choke out many trees and alter the makeup of Southern forests.
IN THE SKY: From David Dundee, Tellus Science Museum astronomer: The moon will be new next weekend. Mercury is low in the west around dusk. Rising in the east are Venus, an hour before dawn; Mars, just after midnight; Jupiter, a few hours after sunset; and Saturn, at dusk.
Charles Seabrook can be reached at email@example.com.