Ground-breaking scientific discoveries and revolutionary technological advances over the past two hundred years have provided humans with the ability to impact the natural environment as never before. Since the beginning of industrialization in Europe and North America in the early 1800s, the world’s population has also increased from one billion to seven billion people. Many estimate that soon nine billion people will live on planet Earth. The human population has grown fourfold since the beginning of the twentieth century, but per capita use of resources has increased much more. Humans today consume about 50 percent more natural resources than only 30 years ago (VanDeveer 2010). At the same time, the world is a very unequal place: approximately one billion people live on less than $1 a day, while over five billion people survive on less than $10 a day. Consequently, some people consume many more natural resources than others during their (greatly varying) lifetimes.