It was, as it turned out, an idea whose time had come. When Nelson got back to Washington, he started gathering support and money to make what soon became known as "Earth Day" a reality. Mayors, governors and students immediately got on board.
By the appointed day, millions of people all over the country were staging events, ranging from mock funerals for the internal combustion engine to demonstrations against polluters, offshore oil drillers, pesticide manufacturers and non-biodegradable detergents.
"It was a big enough demonstration to get the attention of the political establishment and force the issue on the political agenda," Nelson told Christofferson, who wrote "The Man From Clear Lake," the 2004 biography of Nelson. "The public was already there, ahead of the politicians."
As the New York Times' Nan Robertson wrote, "It was Earth Day, and, like Mother's Day, no man in public office could be against it."
Although the next several Earth Days were not as sensational, by the highly publicized 20th anniversary of Earth Day in 1990, "recycling" and "biodegradable" had become common terms in the United States. Worldwide, it was estimated that 200 million people celebrated Earth Day in 136 countries.
Nelson, who was active in environmental issues well into his 80s, took issue with the idea that Earth Day over the years became tepid, saying general knowledge about the issue was "10 or 20 times what it was on Earth Day 1970." In particular, he said, students were much more aware of the dangers to the environment than their counterparts in earlier years.
During his 18 years in the U.S. Senate, Nelson sponsored or co-sponsored many measures on a wide variety of environmental matters, including gas mileage standards, a ban of the pesticide DDT and the Wilderness Act of 1964, which required federal agencies to save some wild areas from logging and mining.
He also helped preserve the 2,100-mile Appalachian Trail, create a national hiking trails system and establish the Apostle Islands National Lakeshore and the St. Croix Wild and Scenic Riverway, both in Wisconsin.
In 1972, George McGovern, the Democratic nominee for president, asked Nelson to run as his vice president.
Nelson declined, however, telling his old friend that he wanted to be able to speak his mind on matters of policy.
McGovern instead picked Missouri Sen. Thomas Eagleton, whom he had to drop when it was disclosed that Eagleton had been hospitalized for depression. (Sargent Shriver replaced Eagleton on the Democratic ticket.)
Nelson, who was among the first senators to oppose the Vietnam War, left public office in 1980 after Republican Robert W. Kasten Jr., who was running on Ronald Reagan's coattails, narrowly defeated him. Nelson subsequently became counselor at the Wilderness Society, a Washington, D.C.-based environmental group.
William H. Meadows, the group's president, called Nelson the "founding father of the modern environmental community."
Besides his wife, Nelson is survived by his sons Gaylord and Jeffrey and his daughter Cynthia.
