PLANET EARTH: Forty three years after Sen. Gaylord Nelson, D-Wis., introduced the idea of Earth Day on the floor of the U.S. Senate, the bipartisan intent to protect America's environment has spread worldwide. Today, April 22, is now an established annual marker, and recognition, that the planet requires careful attention to keep it healthy. This year, according to Earth Day organizers, some one billion people, from China to Brazil to South Africa, intend to participate in the event.

Adamant and persuasive, Sen. Nelson's laid out straightforward goals in 1970: Rid the country of pollution from oil spills, pesticides, detergent, and trash — all those metal cans and bottles tossed out car windows. His work is nowhere near finished, but awareness of toxic pollution and environmentally damaging practices has heightened over the past four decades, thanks to Nelson's clarion call, which seeped into American policies and fed a growing environmental movement.

To see what's happening on earth from the perspective of outer space, visit this NASA blog, with photos shot from satellites.

These NASA maps illustrate how earth’s climate system change from month to month.

Here in Maine, Earth Day coincides with the busiest time of the year, when gardens are readied for planting, towns are sweeping sidewalks and streets, and business owners are sprucing up, getting ready for a long tourist season. It is a naturally-occuring Earth Season that lasts from March until it's time to put it all the gardens back to bed for the winter.

But Earth Day calls on citizens to act as communities, to clean up and protect on a larger, more comprehensive scale. In 1970, Sen. Nelson was outraged by the massive oil spill in Santa Barbara, California. From that beginning, others moved the environmental cause forward over the decades to shape energy policies, and respond to climate change. Earth Day has become a product — and catalyst — of social and environmental change. While Earth Day organizers are hoping this year to galvanize citizens around the world to recognize and act on climate change, others have different perspectives, especially in light of what happened in Boston on Patriot's Day, and the aftermath.

"We all have experienced the feeling of being a community of one during times of hardship like natural disasters or cowardly acts of terrorism," said Camden resident Leonard Lookner, who also serves on the Camden Select Board. He draws parallels between what the world watched as Boston underwent a traumatizing week following the detonation of explosives at the Boston Marathon and the historic intent of Earth Day.

There is light mention of Earth Day across the state this year. An event in Portland at Monument Square was listed at one website, and on Mt. Desert, the National Park Service has waived entrance fees for anyone visiting Acadia National Park, or any other national park across the country for the entire week, hoping that "Americans will have an opportunity to appreciate the beauty and history that lives in these protected areas," the NPS says.

But Boston occupied Maine's thoughts last week, and Earth Day becomes, in a way, an extension of that intense focus on the resiliency of a large community.

"We all wish that we could do something to help, to volunteer a service or perhaps donate some money or food to a family affected by tragedy," said Lookner. "I wish we could find a way to make that feeling of mutual purpose last longer than just a few days. I wish that we could channel that positive energy into a force for good in our society.  Perhaps we can in some small way. Perhaps we can find a way to become a volunteer within our own communities or to do something like to recognize and greet a neighbor or stranger. To let a person get ahead of us at a line in a grocery store or stop to let a car pull out or to park."

Lookner, who also walks a lot, suggests citizens pay attention to the smaller details, as well, on Earth Day.

"Perhaps we can dedicate a small portion of our time to picking up roadside litter," he said. "We can feel that we are making a difference by instilling pride in what we call our Homeland."

Editorial Director Lynda Clancy can be reached at lyndaclancy@penbaypilot.com; 706-6657.