Earth Day 2011 titles itself “A Billion Acts of Green.” But its official website makes no mention of population control, the ultimate green practice.

As long as the most environmentally enlightened Americans ignore the relationship between population growth and environmental sustainability, then America will lose the green fight. In the 1970s, reducing population was so mainstream that biologist and Stanford University professor Paul Ehrlich regularly appeared on the Johnny Carson Show as an advocate. Today, it’s rarely mentioned.

As America approaches 310 million people, on its way to 1 billion unless the current population trend is reversed, here are a few facts compiled by Mother Jones that the 80 percent of young married couples who start families should consider.

From 2000 to 2050, the United States will add 114 million kids to its population. Africa will add 1.2 billion. But because of the high U.S. consumption rate, the respective CO2 emissions of both nations will be identical. During their childhood, many of those U.S. kids will travel to school on buses, 95 percent of which run on diesel and release 3,700 tons of soot and 11 million tons of greenhouse gases annually. School-bus exhaust is linked to higher rates of asthma and lung cancer. After school, kids’ No. 1 pastime is watching television. But up to 223 trees would be required to offset the CO2 produced by a child who watches three hours of TV every day for 18 years. Of course, those kids will have their own kids, so on and on the results of overpopulation will go.

Refusing to talk seriously about population growth also means that American leaders have avoided any discussion of immigration’s role in the crisis. During the past 25 years, the mainstream media and the federal government have consistently advocated for more immigration without any reference to how many immigrants a country concerned for its own ecological and sociological future can accommodate.

The question never asked in the newsroom or on Capitol Hill: “What is the optimum level of annual immigration for a nation that seeks to embrace the highest ethical standards for its citizens and hopes to provide an example to the world that lower population leads to a more compassionate government for all?”

Population growth has momentum. If the United States hopes to avoid the pressures on energy, infrastructure, water, air quality and urban sprawl, to name only a few, then it can’t postpone a meaningful immigration discussion until the nation is squeezed with 500 million people. According to the U.S. Census Bureau, that frightening date could arrive as soon as 2050.

The solution to slowing America’s population is two-fold. First, restore traditional levels of immigration to their pre-1965 200,000 annual average. That would help keep displaced Americans and recently arrived immigrants in the job market. At the same time, advocate for limiting family size. Having two or more children is not an obligation.

The long forgotten “Zero Population Growth” campaign so widely embraced during Ehrlich’s era must be revived and promoted, especially in our classrooms so that future generations will be as aware as we were in the 1970s. ZPG’s philosophy originally outlined four decades ago is more critical today than it was then: “A constantly increasing population is responsible for many of our problems: pollution, violence, loss of values and of individual privacy.”

— Joe Guzzardi has written editorial columns — mostly about immigration and related social issues — since 1990 and is a senior writing fellow for Californians for Population Stabilization (CAPS). After 25 years as an English as a Second Language teacher in the Lodi Unified School District, Guzzardi has retired to Pittsburgh. He can be reached at joeguzzardi@capsweb.org.

Joe Guzzardi is an Institute for Sound Public Policy analyst who has written about immigration for more than 30 years. A California native who now lives in Pittsburgh, he can be reached at jguzzardi@ifspp.org. The opinions expressed are his own.