Seven Billion and Counting

October 31, 2011, marked an uneasy milestone for Planet Earth. On this day, the global population surpassed seven billion. What does that mean for a world that, until the nineteenth century, was home to less than one billion people? Experts say it means the planet is in trouble. Some wonder if Earth will even be able to sustain human life at its current rate of growth.Will there be enough food for...