Tomorrow, Saturday, April 22, is Earth Day. For many reasons, this year’s celebration bears special significance.

The first Earth Day was in 1970 and was celebrated by tens of millions of Americans demonstrating support for protecting the environment. Later that year — eight years after Allegheny County native and Chatham College graduate, Rachel Carson, awakened a global environmental movement with her landmark book, Silent Spring — President Nixon signed an executive order bringing the Environmental Protection Agency into existence. Since that first event 47 years ago, Earth Day has become a worldwide observance — recognized in 192 countries as “the largest secular holiday in the world.”

Earth Day 2017 is about to become even bigger. In November, American voters chose leaders who are — and have been for a long time — openly hostile to policies which protect the environment. (Let’s pause here to make an obvious point: Policies that are written and passed as laws, rules, and standards for “environmental protection” are actually created to protect the health of people, you and me, and not some nebulous tree or forest, salamander or wetland.) These same leaders have, in the first 4 months of this year, brought in equally-hostile bureaucrats and rolled back numerous years-old rules to protect men, women, and children — workers, parents, students, voters — from the harms of air and water pollution emitted by both industries and individuals. While disrespecting the public’s health, these ideological partisans claim, despite mountains of objective, observable, and repeatable scientific evidence, that climate change is a “hoax.” (Let’s pause, again, to highlight an important fact: There are very, very, very few people left in this country and around the world who agree with the statement that “climate change is a hoax.” In fact, a sizable majority of adults in the U.S. — most of whom passed high school science once — subscribe to the ten word pearl about climate change we have heard here before: “Experts agree. It’s real. It’s us. It’s bad. There’s hope.”)

But putting the delusions of our chief executive and his minions aside, what is clear this Earth Day is that protecting the environment goes way beyond protecting a few trees or a few rivers or a few life forms on the Endangered Species List. It even goes beyond preserving whatever cleanliness still exists in our two most precious shared resources — our air and water — to keep humans and all life forms healthy. (As we learned yesterday, attention to these issues by scientists, grassroots environmental organizations, government agencies, legislatures, and judicial bodies has brought this country cleaner air since the first Earth Day. Our country has gone from being a two-pack-a-day smoker to a one-pack-a-day smoker — better but still bad, there is more work to be done.) The environment is humankind’s life support system and we have a long way to go to protect it.

The battle lines over the health of our planet (really the health of the ecosystem that supports the life of humans and other equally important species, so far as Mother Nature is concerned) have been clearly drawn for several decades — certainly since that first Earth Day in 1970. On one hand, there are the “Free Market Fundamentalists,” as Naomi Oreskes and Erik Conway aptly describe them in their highly-recommended book, Merchants of Doubt. In the other corner (wearing the green trunks) are “Environmental Fundamentalists,” a term used by environmental critics like Free Market Fundamentalists. Both terms describe each side of each fight that has played out politically, again and again, for the last half-century, while the vast center of “fair-minded” citizens look for some sort of “balance” between economic development and environmental protections — a balance that, in reality, seldom exists. Tobacco (firsthand and, later, secondhand smoke), acid rain, the ozone hole, and now, climate change — one intensive conflict after another, waged over many years by the same small group of characters, utilizing the same tools of denial of science, obstruction of action, and denigration of the scientific community. And always with the same inevitable victor: Science. Because tobacco products are dangerous to human health (even indirect, secondhand exposure) — sensible regulations on tobacco products to protect health were finally enacted after years of denial and inaction; acid rain is real — and fixing the cause didn’t crater the economy as critics predicted it would after all was said and done; the ozone hole is shrinking now due to smart, evidence-based policies that were finally, after years of denial and obstruction, implemented to stop its expansion; and climate change… well, we’re still waiting for the scientific evidence which is already overwhelming to convince policymakers that it is in our national economic interest (in addition to our public health interest) to act on climate change now, not later, because, you know, it is real.

Earth Day gives us the chance to take a look around the awe-inspiring natural world we are so fortunate enough to experience, to recommit ourselves and our communities to preserve the beauty and resources so precious to life, and to inspire children to learn (from us) to become responsible stewards of the only home we’ve got. It’s another chance to remind ourselves what a wonderful world this really is and that there are no do-overs if we mess things up here. We only live once (and not for very long in the grand scheme, it turns out).

Earth Day 2017 also gives us the opportunity to applaud scientists and the important work they do. It’s not a stretch to think of new parents looking into their baby’s eyes and hoping that someday they will grow up to be a scientist, healthy, on a livable planet, with clean air to breathe and clean water to drink. This Earth Day, people in cities across this country and around the world will gather in support of science, of scientists and their pursuit of truth, and of kindness of the human spirit in defense of health (our’s and the environment’s). For one day, at least, “alternative facts” will take a vacation.

The largest group of supporters will descend on Washington, D.C. tomorrow, but no less than 14 cities and large towns in Pennsylvania are expected to host satellite marches. In Pittsburgh, the event begins at 12:00 PM on the campus of the University of Pittsburgh in front of the Cathedral of Learning.

To find a march near you, step on up over here.