It wasn’t a bunch of tree-hugging flower children who started Earth Day in 1970. It was a U.S. senator from Wisconsin.

Gaylord Nelson was elected governor of Wisconsin in 1959 and U.S. Senator in 1963. He was a lawyer, and saw action with the Army on Okinawa during World War II. Nelson was an advocate for small business, leading the way to the first modern White House Conference on Small Business as chairman of the Senate Small Business Committee, but his real passion was for the environment.

In the 1960s, Nelson’s colleagues in Washington were uninterested in his efforts to get them to take ecological concerns seriously, so Nelson decided to take the issue to the people. He later said, “Earth Day planned itself” after an estimated 20 million people turned out across America to talk about ecological problems in their towns, their states, on their planet and to demand action from elected officials.

It worked. A media spotlight and a people united in a cause led to what’s been called the “Environmental Decade” in which many pieces of legislation were passed to protect the environment, the Clean Water and Clean Air acts among them.

Earth Day is coming around again on Sunday, and organizers have a new way of mobilizing the masses with their “A Billion Acts of Green” campaign. On the Earth Day 2012 website, individuals may pledge to somehow make their lives a little more green. Recent acts of green include “Get a better recycling program started at my company,” “Reduce water consumption,” “Plant new trees with my family” and “Ride my bike to work.”

If a billion people do a billion small things to make the world a better, greener place — it makes a difference.

Visit act.earthday.org to make your difference.