By Dan Shapley
Poison ivy has grown faster, grown stronger, and grown more resilient as the level of atmospheric carbon dioxide has increased in the past 50 years, according to new research. The project builds on a six-year study released last year that showed poison ivy would respond well to future increased in carbon dioxide, no matter how that gas influences global warming. The new research shows that it's already happening. "The change that's already occurred in CO2 does stimulate growth of poison ivy, relative to other species," said the lead author of the peer-reviewed research, Lewis Ziska of the Department of Agriculture. "Poison ivy if you want to divide it into winners and losers is one of the winners." Not only do poison ivy leaves and stems grow larger and more quickly (and the itch-inducing oils seemingly get a boost), but the rash-producing plant rebounds quickly from damage due to pulling, slashing, deer browsing and probably even herbicide use. While Ziska and his colleagues didn't try every manner of insult, other research has shown increased chemical resistance in many weeds at elevated carbon dioxide levels. In general, research indicates weeds like poison ivy will fare better than cultivated plants as the climate changes, they will be harder to eradicate, and they will become more noxious. Weeds which ecologists sometimes call by the much friendlier term "pioneer species" are adapted to colonizing disturbed soil, dispersing seeds widely and more or less rolling with the punches. Homogenous crops are just the opposite designed for one purpose and reliant on humans to plant and care for. Couple development of rural lands with climate change, and you get a weed wielding "one-two punch," Ziska said: "When you disturb the soil, you create a great environment for weed colonization. And the combination of that with variations in the environment supports the perfect one-two punch for getting weeds established, and for them to grow stronger and faster." It will be little consolation to the many people who suffer from itchy rashes from coming into contact with the oil on poison ivy leaves, but poison ivy does have a robust role in its ecosystem. Birds feast on its berries, for instance, and deer and rabbit eat its leaves. "One of the things to keep in mind," Ziska said, "is that whenever there is an environmental change, you can''t just say it's all bad or all good."