The 42nd Earth Day, held April 22, may not be a round milestone anniversary for those celebrating the annual event devoted to raising awareness about environmental issues, but it will come closer than any in recent memory to the spirit of the first Earth Day held across the U.S. in 1970.

That's because just like their predecessors, organizers of this year's Earth Day activities took inspiration from the popular protests happening around the world, choosing the slogan "Mobilize the Earth" as the theme for Earth Day 2012.

"This year, there was a lot of political activity worldwide — from the Middle East to the … Occupy movement," said Kathleen Rogers, president of the Washington, D.C.-based Earth Day Network.

"For 2012, we felt mobilization as a concept was really critical, because it helps people understand that they can actually get going, they actually can get something done."

Rogers's group works with thousands of organizations and governments in almost 200 countries to promote and help organize Earth Day activities and to raise environmental awareness year-round. It grew out of the group that organized the first Earth Day and still has one of the movement's founders, Denis Hayes, on its board of directors.

Anti-war protests inspired 1st Earth Day

Gaylord Nelson made conservation a key focus of his two terms as governor of Wisconsin and continued to champion environmental issues in the U.S. Senate, organizing the first Earth Day in 1970. (Alex Wong/Getty )

The idea for Earth Day was born in the U.S. at the tail end of the1960s amid the heated student protests opposing the Vietnam War. Founder Gaylord Nelson, a Democratic senator from Wisconsin who earned a reputation as a passionate conservationist during his two terms as governor of the state, was impressed by the passion driving the protest movement. He modelled the first Earth Day on the teach-ins that anti-war activists were holding on college campuses to educate students about America's involvement in the Vietnam War.

Nelson, who died in 2005, and his fellow organizers made environmental issues the focus of their "national teach-ins," and there was plenty to focus on in 1970.

Unchecked industrialization and urban sprawl had made air pollution a concern in many large American cities; the harmful effects of DDT and other pesticides were also on the public consciousness ever since the 1962 publishing of Rachel Carson's seminal book Silent Spring; and two high-profile incidents in 1969 put industrial pollution and its impact on the environment top of mind.

The two incidents were a blow-out on an Union Oil drilling rig off the coast of Santa Barbara that spilled 11.4 million litres of oil into the ocean, angering Californians who saw the devastating effects on their beaches and marine life, and a fire on the heavily polluted Cuyahoga River in Cleveland that drew attention to the industrial waste that had for years been voided into the waterway.

'One of the central goals of the event was to tie all of these diverse strands of environmentalism … together with one bow and make them recognize that they're part of a coherent movement.' — Denis Hayes, co-founder of Earth Day

But the first Earth Day was much more than a day of protest: it was the beginning of the environmental movement in North America, says Hayes, who was the national co-ordinator of the first Earth Day events in 1970 and has remained involved in Earth Day activities and the environmental movement.

"One of the central goals of the event was to tie all of these diverse strands of environmentalism — people who were concerned about pesticides, people who were fighting freeways, people who hated air pollution, people who were worried because rivers were catching on fire — to tie them all together with one bow and make them recognize that they're part of a coherent movement," said Hayes, who today heads the Bullitt Foundation, a Seattle-based environmental organization.

1970 event spawned landmark legislation

Hayes was a 25-year-old university student when Nelson recruited him for his ambitious Earth Day initiative. He was interested in changing people's understanding of ecology and broadening the definition of environmentalism to include everything from eradicating nuclear and chemical weapons to promoting organic gardening, but he never thought the consciousness-raising rallies and activities he helped organize in 1970 would go on to have such a long-lasting impact.

A firefighting tug boat douses flames on the Cuyahoga River in Cleveland on June 25, 1952, after oil and other industrial waste caught fire. A similar fire broke out in 1969 and prompted widespread public anger at the growing prevalence of industrial pollution in U.S. cities. (Associated Press)

Not only did the events themselves draw about 20 million people — from all walks of life and, thanks to Nelson's bipartisan efforts to include his Republican colleagues in the movement, from across the left-right political divide — the attention Earth Day brought to air and water issues in particular led directly to several key developments in U.S. environmental regulation.

They included the creation of the Environmental Protection Agency and the passing of the Clean Air Act later that year, the adoption of the Clean Water Act in 1972 and the passing of the Endangered Species Act in 1973.

"I'd be hard pressed to think of legislation in the last decade that begins to approximate the kinds of groundbreaking things that we had in the 1970 to the 1975 period," Hayes said.

The environmental laws passed in the 1970s, including in Canada, which passed the Canada Water Act in 1970 and created a Department of the Environment in 1971, were revolutionary in part because they linked environmental issues to public health, says Rogers.

"Prior to Earth Day, the laws were all about species conservation — primarily to [ensure hunters could] shoot them — or land conservation, like national parks," she said. "Earth Day 1970 is definitely the Maginot Line that was there, and everything that crossed over became about health and people, not animals and shooting and parks. It became about human beings more than anything."

Although it's harder to draw a direct line between the Earth Days of subsequent decades and substantive changes in environmental regulation, the day has remained relevant as a driver of environmental education and awareness.

1990s focused on changing behaviour

Students assemble a five-storey globe on the National Mall in Washington, D.C., in preparation for the 25th anniversary of Earth Day in 1995. The '90s saw the environmental movement shift focus away from trying to change federal legislation onto changing individual behaviour. (Joyce Naltchayan/AFP/Getty)

After a lull in activity during the 1980s, when, says Hayes, the day seemed to have "outlived its usefulness," the Earth Day movement was re-energized in 1990. In part, it was a reaction to eight years of an administration, under President Ronald Reagan, that was seen as hostile to environmental causes and that had, in the eyes of many, stalled or rolled back progress on air pollution, toxic waste and land and water conservation.

"In 1990, it began this shift away from focusing upon big federal pieces of legislation to the roles of states and, even more, communities and beyond that individuals," Hayes said. "The overall theme was 'Who says you can't save the world?' — trying to be feisty but get people to say this isn't all just a matter of getting Congress to pass some laws. This has to do with your choices as a consumer, your choices as an automobile- and home-owner, your choices as a parent."

The shift to environmentalism as a personal responsibility worked: between 1988 and 1992, the number of curbside recycling programs in North America exploded.

A worker plants a mangrove tree at a conservation garden in Jakarta, Indonesia, to mark Earth Day 2009. These days, Earth Day is very much a global affair, with close to 200 countries participating. (Dadang Tri /Reuters)

"I don't know of any other major thing that contributed to that except that emphasis back in Earth Day 1990," said Hayes.

Nineteen-ninety was also the year that Earth Day activities went global, expanding to more than 140 countries, including Canada.

Today, the Earth Day Network regularly works with groups and governments in countries as far afield as Oman, Morocco and Jamaica, organizing environmental lessons in schools and helping locals address their particular environmental concerns.

An while each jurisdiction tailors its Earth Day activities around the problems in that region, those who participate, says Rogers, see themselves as part of a "global environmental commons."

"Pollution from China hits L.A. in 48 to 50 hours, depending on the trade winds," she said. "People get that what you do in Brazil impacts our oxygen — mine or my kids' — and they're also connecting environmentalism to products. That's the big, significant change for the 21st century: that we get what's going on worldwide."

The climate-change conundrum

Over 40-plus years, Earth Day has come to be associated with all kinds of things its originators never dreamed of. And while it has always included a variety of activities from litter pick-ups and school composting programs to large urban rallies, in recent years it has increasingly also been used as an excuse to sell products or "green wash" corporations and governments that otherwise do little for the environment. (China, which despite its recent embrace of renewable energy and green technologies has an abysmal environmental record, issues an annual Earth Day stamp, for example).

A crowd gathers on Parliament Hill to celebrate Earth Day, April 22, 1990, the first year that Canada celebrated Earth Day. (Frank Gunn /Canadian Press)

"Gaylord and Denis a long time ago decided not to trademark or copyright [Earth Day]," said Rogers. "What it means is you get a wide variety of activities under the auspices of Earth Day. We've seen some pretty bad ones over the years. A mattress company will have an Earth Day sale — it's so random. You're, like, that's so ridiculous, but people then recognize Earth Day, and that’s OK."

Hayes, 67, will be taking part in Earth Day activities on the National Mall in Washington this April 22, and he says this year's call to "mobilize" the populace is well placed.

"The 2000s, somewhat to my surprise, have become extremely divisive on environmental issues," Hayes said.

The 21st century, says Hayes, has pitted environmentalists trying to raise the alarm about climate change against those in industry and government waging a campaign to downplay the threat, discredit the science and protect economic interests dependent on fossil fuels.

Denis Hayes, one of the founders of Earth Day speaks at a rally denouncing the environmental policies of U.S. President George W. Bush in Washington, D.C. (Alex Wong/Newsmakers)

"They tend to deal with slogans and populist rhetoric, and the [environmental] movement has come back with things that are studious and balanced and nuanced and polysyllabic," said Hayes.

"In 1970, we talked about poison. In 2000, we tended to talk about polycyclic aromatic hydrocarbons. 'Poison' is a more effective thing to say, and we're in the process of trying to learn once again how to communicate broadly with the population."

To date, Earth Day organizers — and the environmental movement in general — have not been as successful in getting people to care about global issues like climate change as the Earth Day instigators of the 1970s were in getting them to care about air and water pollution, which while also global issues could more easily be made local.

"People will get more engaged in ways that have political consequences to the extent that they see it affecting them or their families directly," Hayes said. "People care about the future of the world, but that's kind of an abstract concept."

Hayes says that's changing as more people begin to understand that climate change is not unrelated to the hurricanes, tornadoes, droughts and wildfires that occur in their communities

An Arab Spring for the climate

As part of the effort to mobilize the public to tackle climate change, several U.S. environmental groups plan to launch a large initiative in 2013 based around engaging young people through social media and crowdsourcing ideas on green technologies, renewable energy and others means of mitigating the factors contributing to climate change.

The aim, says Hayes, is to create "a huge public consensus-building exercise that hopefully will have some political consequences."

"In a sense, it's a climatic Arab Spring," said Hayes. "Climate has been mostly a television issue. It's something where people preach at other people or, in the case of Al Gore's movie, they provide a film, and you go and you watch it. But it's not a computer kind of issue where you are involved and engaged in doing something yourself.

"What we're trying to do is make that transition, so it's not just passive receptacles of information, but people who engage in it, challenge things and become committed to acting on the basis of their growing understanding of what's really going on."