It’s sad to face another Earth Day now that the environmental giants have passed from the scene. By “giants” I mean persons of stature who truthfully made the connection between immigration, overpopulation and environmental damage — leaders like Senator Gaylord Nelson and Sierra Club President David Brower. These days, the Congress is filled with people who call themselves environmentalists but vote for open borders, and the Sierra Club has gone over to the dark side as completely as Anakin Skywalker became Darth Vader.

But back to Gaylord Nelson… In 2004, the University of Wisconsin presented the retired Senator with a Distinguished Alumni Award, which included a brief film about his life’s work:

Environmental scientist Leon Kolankiewicz wrote up an Earth Day remembrance of Senator Nelson as a reminder of how a real environmentalist acts.

Earth Day founder disappointed in followers for neglecting overpopulation, Mother Nature Network, April 20, 2010

This month, America celebrates the 40th anniversary of Earth Day, founded in 1970 by the late U.S. Sen. Gaylord Nelson (D-Wis.), one of our greatest environmental heroes of the 20th century. Yet few of the multitudinous articles, exhibits, parades and speeches will dare — or bother — to broach the one issue that worried Nelson perhaps more than any other: human overpopulation.

I know this because I collaborated closely with Nelson on several projects during the last decade of his life.

By the time he died in 2005 at the age of 89, Nelson had become deeply disappointed with the wholesale retreat of the environmental establishment from advocating limits to population growth. Rather, a new generation of more pragmatic (expedient?) campaigners preferred to prattle on about safer and sexier topics like tropical deforestation, overfishing, oil and water shortages, urban sprawl, traffic congestion, power plant pollution, toxic waste, marine “dead zones,” proliferating dams, roads and power lines, destruction of wildlife habitat, endangered species, and of course, climate change. Ironic when human reproduction and the population growth it produces are all about sex, eh?

Nelson and many other activists of his generation viewed these problems as symptoms of too many people consuming too many resources and generating too much waste. In an influential 1971 paper published in the journal Science, biologist Paul Ehrlich and physicist John Holdren (now President Obama’s science adviser) quantified this understanding by introducing the IPAT equation: Impact = Population x Affluence x Technology.

Environmentalists of that era largely endorsed this formulation, which explicitly included the population factor, and even wide segments of the broader American public were receptive to it. The outspoken Ehrlich appeared several times on The Tonight Show with Johnny Carson to hammer home his “zero population growth” message to millions. And for a variety of reasons, the fertility rate plummeted by about half from its baby boom high down to replacement level — 2.1 children per family — by the early ’70s.

After two centuries of continuous exponential expansion — from a puny 4 million in 1790 to a bulging 200 million in 1970 — America seemed poised to voluntarily and humanely halt population growth before it overwhelmed our environment. With U.S. population stabilization, our beleaguered environment could have begun to breathe a sigh of relief from ever-increasing demographic demands for land and resources.

Yet this hopeful vision did not come to pass. Instead of stabilizing, America has added more than 100 million new voracious consumers, each brainwashed daily by powerful commercial interests that through conspicuous consumption we can achieve nirvana, or at least keep up with the Joneses.

Americans now number 310 million, and the Census Bureau projects another 130 million by 2050, pushing us to 440 million. And we would still be growing rapidly with no end in sight! Under this crushing pressure, virtually every environmental goal becomes unattainable, from reducing our national ecological footprint and carbon emissions to rescuing endangered species and ecosystems. Achieving these will be mission impossible, as much a pipe dream as losing weight and getting fitter all while eating more and more.

And yet today’s environmentalist leaders are strangely silent in the face of this unfolding demographic disaster. Why? Because immigration, or “the i-word,” since environmental groups dare not utter it, is now pushing our population upward. Over 80 percent of the projected increase to 2050 will be due to directly and indirectly to immigration. Fearful of alienating progressive allies and growing numbers of Hispanics and Asians, and loath to be lumped (however unfairly) with repugnant xenophobes, the largely white, liberal, and yes, squeamish environmental establishment either opts to look the other way on population — or they insist it is a “global problem that needs global solutions,” thereby abrogating the need for any meaningful action on their part. Never mind that, on a planet dominated by sovereign nation-states, there are literally no realistic means available to work at a “global” scale.

But liberal, Democratic icon Gaylord Nelson did not flinch or look the other way or frame the problem so vaguely as to preclude national action. His many speeches on environmental sustainability continually highlighted the U.S. population problem. A newspaper article describing one Earth Day speech began: “Senator Gaylord Nelson spoke to a standing-room only audience advocating that the U.S. limit immigration before U.S. resources are depleted.” At a Washington press conference, Nelson bristled at the notion that limiting immigration is inherently racist.

In a March 2000 speech, Nelson warned that the U.S. could become as overpopulated as China and India. “With twice the population, will there be any wilderness left? Any quiet place? Any habitat for song birds? Waterfalls? Other wild creatures? Not much,” he said.

Chatting with Nelson before a 1998 news conference at the National Press Club in Washington, he startled me by announcing that when all was said and done, he considered himself a failure because the U.S. was moving away from, not toward, sustainability. And out-of-control population growth was a major reason why.

But Nelson did not fail. His followers failed him … and the nation’s environment they purport to defend.