"We are up to our arms in poison ivy this summer," said Ziska, with the USDA's Agricultural Research Service in Beltsville, Md. The higher CO2 levels, he said, also are contributing to an increasing abundance of kudzu, the legendary vine once limited to the South but was discovered lurking in central Illinois and as far north as Canada. Dr. Paul Epstein, associate director for the Center for Health and the Global Environment at Harvard Medical School, said recent studies show that poison ivy is not only more prevalent across the U.S. but more toxic, too. The rise in CO2 levels strengthens an oil in the plant that triggers itchy havoc when it touches the skin, he said. The heavy rains, warmer temperatures and rising CO2 levels that have disturbed plant chemistry also have increased pollen counts, leading to higher rates of asthma and allergies. "It's not an accident we're having this perfect storm," said Epstein. "Pests and pathogens thrive in extreme events, like floods or droughts. We need to stabilize the climate by reducing fossil fuel emissions dramatically." John Masiunas, an associate professor in the Department of Crop Sciences at the University of Illinois Urbana- Champaign, said he is unaware of any quantitative data tracking an increase in poison ivy taking root across the state. But, he said, "it makes perfect sense that higher CO2 levels will make these plants more efficient." The plant has "a survivor's ability" to grow in a variety of environments, Masiunas said, adding that climate change is also detrimental to endangered species such as native thistles and orchids that require specific soils and pollinators to thrive. "When climate change occurs … it is poor for these plants and contributes to the extinction of the species," Masiunas said. "When endangered plants are competing in an agricultural ecosystem, they start losing, and plants like poison ivy start doing better."
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