On October 31, 2011, the United Nations is expected to announce a projected world population figure of 7 billion. This global milestone presents both an opportunity and a challenge for the planet. While more people are living longer and healthier lives, says the U.N., gaps between rich and poor are widening and more people than ever are vulnerable to food insecurity and water shortages. Because censuses are infrequent and incomplete, no one knows the precise date that we will hit the 7 billion mark - the Census Bureau puts it somewhere next March. In the last 50 years, humanity has more than doubled. What could the next decade mean for our numbers and the planet? In this post, we focus on births, but we'll be back with population-related content including it's affect on the environment and our food supply. -- Paula Nelson ( 47 photos total