Most of our serious problems in the world today can be traced back to the impact of human populations on the environment. With each person requiring energy, space and resources to survive, the stress on the planet of the world population, currently estimated to be seven billion, is enormous. Richard Cardullo, a professor of biology at the University of California, Riverside, discusses how human populations have grown at an alarming rate over the past few centuries and discuss some of its consequences. Series: "Earth 101: What You Need to Know About Life on our Planet" [Science] [Show ID: 24206]