Population 7 billion…in the past 50yrs alone the population has doubled! Yikes

Favela Joaquim de Queiros, a hillside neighborhood of Rio de Janeiro, Brazil, viewed from above via Google Earth.
“The United Nations Population Fund estimates that in one week, on October 31, 2011, the world’s population will reach 7 billion. Just 200 years ago, there were only 1 billion people on the planet, and over the next 150 years, that number grew to 3 billion. But in the past 50 years, the global population has more than doubled, and the UN projects that it could possibly grow to 15 billion by the year 2100. As the international organization points out, this increasing rate of change brings with it enormous challenges.” Source: www.theatlantic.com
For most of us population growth has not been something we think much about. I mean, humans have sex, have babies and have the right to have as many as they want. But is this really working out for a harmonious planet? Where do we go from here? The consumption rates of regions like North America and the UK already require us to need another 3 earths to survive the next couple decades… where are we gonna get those extra planets from?
What are your thoughts?