Occupy Planets: Environmental Footprints and Sustainability

There are 7 billion people in the world. In the past dozen years the Earth’s population has grown by about 1 billion. If all 7 billion lived like the average United States resident, how many planets do you think we’d need? I asked that question of 10 classmates at Michigan State University in East Lansing, Mich. Most said their environmental footprint would be about average.