A Soupçon of Poison in the Air

Poison ivy.  Its scientific name says it all: Toxicodendron radicans,” or “an easily-rooted poisonous tree,” as farmers and gardeners know all too well.  A native woody low shrub that is erect or trailing, or is a climbing vine, the plant is well known for its ability to produce urushiol, an oily skin irritant that causes an itching rash for most people.  And, for some of us unfortunates, reactions to poison ivy can even progress to anaphylaxis.  What a sinister chemical arsenal evolved by this species and its relatives!

It’s a member of the plant family, Anacardiaceae, that includes cashews, mangos, pistachios, and the gum mastic tree used in chewing gums and dental adhesives.  One of the commonalities of all these plants is the presence of that nasty allergen, urushiol.  All of them have it somewhere in their lovely plant bodies so they’re often peeled, roasted, or otherwise altered in the manufacture process to rid the product of this chemical.

Though it’s an important food for wildlife such as white-tailed deer, black bear, cottontail rabbits, game birds, and woodpeckers, most people – an estimated 85-90% of the human population – are highly susceptible to the skin irritant produced by poison ivy.  Even one billionth of a gram of the sticky, resin-like urushiol will trigger a skin reaction.  In fact, one-quarter ounce of the stuff would be enough to cause a rash for the entire human population on Earth!

Thus, we all need to recognize poison ivy in all its variations.  Various mnemonic rhymes describe its appearance to help us avoid the plant altogether:

• “Leaves of three, don’t touch me.”

• “Hairy vine, no friend of mine.”

• “Berries white, danger in sight.”

Urushiol remains active in poison ivy throughout the year, even in the dead of winter.  So beware!

And now for some scary news about Toxicodendron radicans.  Due to climate change, it’s spreading like wildfire.  New research from the U.S. Department of Agriculture, Duke University, and other organizations suggests that poison ivy is growing faster and producing more potent oil compared with earlier decades.  Apparently, rising ambient levels of carbon dioxide create ideal conditions for the plant, producing bigger leaves, faster growth, hardier plants, and an oil that’s even more irritating.  Studies have already found that a higher level of carbon dioxide doubled the growth rate of poison ivy, and it made for hardier plants that recovered more quickly from the ravages of grazing animals.  In other words, because of human-accelerated climate change, we’re inadvertently creating “super poison ivy” across its range in North America.

The naysayers about climate change have their heads in the sand.  Not only do we have incontrovertible, systemic evidence about the physical changes in the global atmosphere, but now we have ample biological indicators that point to the insidious, long-lasting consequences of poor land management and our maddening reliance on carbon-based industries and transportation.  These responses in poison ivy provide just a few indications that human-accelerated climate change is upon us.  Until we transition away from heavy deforestation and near-exclusive reliance on oil, coal, and natural gas, we will continue to see similar reactions in biodiversity across the planet’s living landscape.  There’s a hint of poison in the air that’s beginning to transform life itself.

If you like the idea of poison ivy becoming a super-organism, then turn your back on global climate change.  If you do not, then let’s demand a responsible energy policy for the nation that considers our grandchildren more highly than the quarterly stockholder statements for supercilious oil company executives and fickle politicians.