During the first Earth Day in 1970, environmental activist Stephanie Mills made headlines when she announced she would not reproduce to avoid contributing to climate change and other environmental problems attributed to a growing human population. Forty-one years later, should reducing population again be considered as a way to contain global energy demand?

Japan's nuclear catastrophe and the explosion in the Deepwater Horizon oil rig in the Gulf of Mexico a year ago force the question. Nuclear advocates universally justify the decision to fuel power plants with radioactive uranium as the best way to sate the world's increasing appetite for energy. Coal-fired utilities and oil companies use a "running to stay in place" argument as well. Despite gains in efficiency, they correctly point out, energy demand is on the rise. Part of the reason is because people in developing countries are justifiably using more kilowatts of electricity and barrels of oil to help bring their standard of living up to that of countries that have abundant energy access 24/7. But another reason is because every year, says the United Nations, our global numbers increase by some 80 million people, the equivalent of ten New York cities. At that rate, world population is projected to spike from the current 6.9 billion people to over 9 billion by 2044.

We don't have to wait thirty-three years to comprehend the impact increasing population growth will have on energy consumption and the resulting carbon dioxide that contributes to climate change. According to the International Energy Agency, from 2004-2008, world population increased 5%. During the same period, gross energy production increased 10% with a comparable 10% jump in annual CO2 emissions.

This does not bode well for our energy future.

Yes, we can wring another 4-12% out of every kilowatt we generate by insulating homes and buildings and improving appliance efficiency, reports the American Council for an Energy Efficient Economy, saving up to $35 billion in the U.S. alone over the next twenty years. Still, as long as population climbs, conservation won't be enough. "The idea that we can trim our energy consumption to come into balance with nature looks increasingly naïve," says population expert Robert Engelman of the environmentalist Worldwatch Institute.

Neither can we afford to meet growing demand by relying primarily on the same problematic energy sources that led to the tragedies in the Gulf or Japan. Radioactive fallout from Japan's crippled reactor has led to fears of it reaching the northwest coast of North America. Gulf coast communities from Louisiana to Florida are still recovering from the oil spill there as the projected clean up and recovery price tag looms at $10 billion or more. Carbon dioxide emissions from burning fossil fuels continue to raise earth's temperature, wreaking havoc on the world's climate from the North Pole to the South. Meanwhile, only 4% of U.S. electricity comes from safe renewable sources like solar, wind and geothermal compared to 45% from coal and 20% from nuclear power plants, as well as 23% from natural gas and 7% from hydroelectric. The percentage of vehicles running on biofuels instead of fossil fuels is almost too small to be measured.

Accelerating the development of clean energy is critical, as is maximizing energy efficiency. But neither strategy will be enough if we don't set our sights on a world where population actually decreases over time.

That may not be as difficult as it seems. Every country that offers easy access to contraceptive and safe abortion services also has a fertility rate of two children per woman or fewer, consistent with a declining population, notes Worldwatch's Engelman. Further, he says, more than two out of five pregnancies worldwide are unintended, suggesting that a world in which women everywhere were fully in control of their childbearing would soon reverse population growth.

What will be difficult, however, is maintaining the federal funding that keeps many family planning programs operating here in the U.S. as well as abroad. The 2011 budget compromise requires Federal lawmakers to cut $38 billion in spending. Though President Obama staunchly supports family planning, Republicans in the House have already proposed more than $200 million in cuts for the international family planning programs the U.S. helps fund abroad. If they succeed, as many as 7 million women could lose access to contraception, reports the non-profit group Population Connection, formerly known as ZPG or Zero Population Growth. Republicans have also proposed eliminating all funding for Title X, the 40-year-old grant program that provides family planning and reproductive health services to American women and men at more than 4,500 health centers nationwide.

Energy demand and population growth go hand in hand. If the U.S. is serious about reducing its energy needs, supporting family planning must be part of the strategy.

Diane MacEachern is the author of Big Green Purse: Use Your Spending Power to Create a Cleaner, Greener World.