The clashing, clanging noises of the late 1960s and early 1970s, now faded after half a century, did not produce as much change as people hoped. But somehow in all that stirred-up social ground a tiny seedling took root.

Earth Day got its start on April 22, 1970. According to Wikipedia, “United States Senator Gaylord Nelson proposed the idea to hold a nationwide environmental teach-in on April 22, 1970. He hired a young activist, Denis Hayes, to be the National Coordinator. … Denis and his staff grew the event beyond the original idea for a teach-in to include the entire United States. More than 20 million people poured out on the streets, and the first Earth Day remains the largest single-day protest in human history.”

Auspicious beginnings. What has been accomplished? What remains to be done?

The first 10 years, says Wikipedia, saw under Presidents Nixon and Carter enactment of the Clean Air Act, Clean Water Act, Endangered Species Act, Marine Mammal Protection Act, Superfu...