A devastating oil spill off the coast of Santa Barbara inspired former Wisconsin Sen. Gaylord Nelson to create the first Earth Day in 1970. Twenty million Americans participated in events as Nelson and other conservationists noted that “every environmental problem is a population problem.”

Nelson knew that stopping population growth was the key to protecting the environment, yet since that first Earth Day, the U.S. population has soared from 203 million to 330 million, and global population has doubled to 7.6 billion.

Californians for Population Stabilization (CAPS) is launching a digital ad campaign to remind us that continuing population growth is the fundamental environmental problem.

“Overpopulation is the root cause of so much environmental destruction —loss of open space, air and water pollution, traffic congestion, and never-ending sprawl,” said Ric Oberlink, executive director of CAPS. “Habitat loss due to population growth is the greatest threat to wildlife.”

California is home to some of the most varied wildlife habitat on earth, boasting more endemic species than any other state, but rapid population growth imperils this extraordinary biodiversity. Over one-fourth of California’s plants are extinct, rare, endangered or threatened, and over 150 animals are listed as threatened or endangered.

Since the first Earth Day, California’s population has doubled to 40 million and the state’s population density exceeds that of Europe. Unlike 1970, current U.S. and California population growth stems almost entirely from foreign immigration.

According to the Pew Research Center, “Future immigrants and their descendants … are projected to account for 88 percent of the U.S. population increase,” between now and 2065.

“Overpopulation is perhaps the biggest problem facing us, and immigration is part of that problem. It has to be addressed,” said Tte late David Brower, a CAPS Advisory Board member and the Sierra Club’s first executive director.

Earth Day founder Nelson was equally forthright in drawing the links among population, immigration and the environment. “In this country, it’s phony to say ‘I’m for the environment but not for limiting immigration,’” he said.

To view Earth Day at 50: A Message from its Founder on Environmentalism, Population Growth, and Immigration, visit capsweb.org.