Glossary of "Environmental Science: Earth as a Living Planet (2nd ed.)" by Botkin & Keller (1998)
- A set of ethical principles that affirm the right of all resources, including plants, animals and earth materials, to continued existence and, at least in some locations, to continued existence in a natural state.
- Botkin, D. B. & Keller, E. A. 1998. Environmental Science: Earth as a Living Planet, 2nd ed. -xxxxii + 649 pp. John Wiley & Sons, Inc., New York.