The RISE of Opportunist WEEDS

Be prepared to see increasing changes in weeds we fight, such as poison hemlock and poison ivy, and in the crops we grow.

- SUSAN BRACKNEY

Poison hemlock, poison ivy and other nuisance plants have been gaining ground over the last several years. In some cases, they’re also becom­ ing more potent. “As the climate is changing, there’s a lot of change in migration of where a particular plant will grow,” says Lewis Ziska, an associate professor in Environ­ mental Health Sciences at Columbia Univer sity’s Mailman School of Public Health. He’s also the author of Agriculture, Climate Change, and Food Security in the 21st Century: Our Daily Bread. He looks at the plant biology parts of climate change. “That’s everything from pollen and allergies to poison ivy to pesticide use,” he says. “Poison hemlock tends to grow in open, sunny areas, fields, vacant lots and so forth. So, it’s fairly common — particularly in disturbed areas.”

ON THE MOVE

If poison hemlock follows the path that other opportunistic, invasive species have lately, it will likely head northward. In part, that’s due to warming temperatures. However, increasing disturbances to our landscapes from wildfires, flooding and other extreme weather events also contribute to the problem.

“If it’s a natural disturbance like a hurricane that goes through and removes all of the nor­ mal vegetation, that provides an opportunity for these species to come in,” Ziska says.

EXTRA POISONOUS IVY?