Another reason to worry about global warming: poison ivy!

Duke University researchers report that poison ivy grows bigger and faster as carbon dioxide levels in the atmosphere rise.

The study appears in the Proceedings of the National Academy of Sciences.

Proc. Natl. Acad. Sci. USA,Environmental Sciences-Biological SciencesBiomass and toxicity responses of poison ivy (Toxicodendron radicans) to elevated atmospheric CO2
( global change forest ecology Rhus radicans ) Jacqueline E. Mohan *, Lewis H. Ziska ¶, William H. Schlesinger *, Richard B. Thomas **, Richard C. Sicher ¶, Kate George ¶, and James S. Clark *
*Department of Biology and Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708; Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138; Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543; ¶Agricultural Research Service, Crop Systems, and Global Change Laboratory, U.S. Department of Agriculture, Beltsville, MD 20705; and **Department of Biology, West Virginia University, Morgantown, WV 26506
Contributed by William H. Schlesinger, April 22, 2006
Contact with poison ivy (Toxicodendron radicans) is one of the most widely reported ailments at poison centers in the United States, and this plant has been introduced throughout the world, where it occurs with other allergenic members of the cashew family (Anacardiaceae). Approximately 80% of humans develop dermatitis upon exposure to the carbon-based active compound, urushiol. It is not known how poison ivy might respond to increasing concentrations of atmospheric carbon dioxide (CO2), but previous work done in controlled growth chambers shows that other vines exhibit large growth enhancement from elevated CO2. Rising CO2 is potentially responsible for the increased vine abundance that is inhibiting forest regeneration and increasing tree mortality around the world. In this 6-year study at the Duke University Free-Air CO2 Enrichment experiment, we show that elevated atmospheric CO2 in an intact forest ecosystem increases photosynthesis, water use efficiency, growth, and population biomass of poison ivy. The CO2 growth stimulation exceeds that of most other woody species. Furthermore, high-CO2 plants produce a more allergenic form of urushiol. Our results indicate that Toxicodendron taxa will become more abundant and more "toxic" in the future, potentially affecting global forest dynamics and human health.