Sometime in the 19th century, as St. Patrick's Day parades were flourishing, wearing the color green became a show of commitment to Ireland, Meagher said.
In 1962 the show of solidarity took a spectacular turn in Chicago when the city decided to dye a portion of the Chicago River green.
The tradition started when parade organizer Steve Bailey, head of a plumbers' union, noticed how a dye used to detect river pollution had stained a colleague's overalls a brilliant green, according to greenchicagoriver.com.
Why not, Bailey thought, turn the river green on St. Patrick's Day? So began the tradition.
The environmental impact of the dye is minimal compared with sources of pollution such as bacteria from sewage-treatment plants, said Margaret Frisbie, the executive director of the advocacy group Friends of the Chicago River.
Her group focuses instead on turning the Chicago River into a welcoming habitat full of fish, herons, turtles, and beavers.
If the river becomes a wildlife haven, the thinking goes, Chicagoans won't want to dye their river green.
"Our hope is that, as the river continues to improve, ultimately people can get excited about celebrating St. Patrick's Day different ways," she said.
via news.nationalgeographic.com
So that's the modern impact. But what about the ecological impact of snake genocide (is there a scientific word for that?) in Ireland?
Another St. Patrick myth is the claim that he banished snakes from Ireland.
It's true no snakes exist on the island today, Freeman said. But they never did.
Ireland, after all, is surrounded by icy ocean waters—much too cold to allow snakes to migrate from Britain or anywhere else.
But since snakes often represent evil in literature, "when Patrick drives the snakes out of Ireland, it is symbolically saying he drove the old, evil, pagan ways out of Ireland [and] brought in a new age," Freeman said.
I hate symbolism.
