On 22 April 1970, World Earth Day was established, born out of the need to protect the environment and natural resources. The movement originated in the United States, and on that occasion approximately twenty million American citizens mobilised in a historic demonstration in defence of the environment.

Public opinion was beginning to grow seriously concerned about the lack of effective environmental regulation. Following the publication of the bestseller Silent Spring by Rachel Carson in 1962, Americans had begun to question the rampant use of pesticides. People were starting to ask questions about the relationship between pollution and health; however, a strong signal needed to be sent to institutions — a statement of intent.

The idea came to Democratic Senator from Wisconsin, Gaylord Nelson: after watching thousands of students take to the streets to protest against the Vietnam War, he understood that this was the path to follow in order to revolutionise the environmental movement: a major national environmental demonstration.

In September 1969, Nelson, at a public event, announced that a major environmental demonstration would take place in the spring of 1970 and invited all interested citizens to take part. The event was therefore organised in a short time and with virtually no budget. "Earth Day worked precisely because it was a spontaneous, grassroots event," Gaylord Nelson recounted.

It was a defining moment for the environmental movement; people had tremendous passion and wanted to play an active part in a movement that could change the world. One of those people was Martin Jennings, a seventeen-year-old from Florida who volunteered to clean up his town's waterways and plastered posters everywhere bearing the slogan that would later become famous: "If you're not part of the solution, you're part of the problem."

"At the time there was so much excitement, a genuine passion that was infectious — we thought we could make a difference," Martin Jennings declared. Thanks in large part to the efforts of volunteers, most of them very young, the first Earth Day demonstration was a success and saw the participation of millions of protesters across the United States.

The scale of events ranged from small school assemblies to the enormous "human river" of over 100,000 people that poured onto Fifth Avenue in New York. The birth of Earth Day was not merely symbolic — it made it possible to achieve concrete results.

Shortly afterwards, 28 environmental reforms were passed, covering the protection of water and air, the proper disposal of hazardous waste, and the restriction of chemicals and pesticides in food and medicines. Since then, many gains have been made, but the planet is still in danger; new challenges must be met, rediscovering the passion and courage that drove millions of people on a distant spring day in 1970.