In 1999, the world’s population was 6 billion. U.S. Census Bureau figures tell us that today the number has increased to 6.7 billion. Best estimates are that we will pass the 7 billion mark in 2012.

William Frey, a demographer with the Brookings Institution in Washington says there is no consensus on how many people the Earth can actually sustain but that it probably depends on how well people manage the Earth’s resources. Today, the U.S. ranks third in population behind China and India.

For far too long, we Americans have consumed oil and other carbon-based fuels suc...