Security threats today are increasingly complex, dynamic, and asymmetric, and can affect environmental factors like energy, water, and food supply. As a result, it is becoming evident that the traditional model of nation-state based security is incomplete, and that purely military capabilities, though necessary, are insufficient to protect the United States and other democracies from the array of threats that challenge liberty and the free flow of people and commerce. A more complete picture of modern national security requires a more complete integration of the question of environmental security.The purpose of text is to better address the many aspects of environmental security and to represent this major area of academic research in an introductory text format that can be used in the rapidly growing number of homeland security studies programs as well as related degree programs. The concepts, challenges, and case studies in this text vitally extended such curricula, giving students a deeper appreciation for the critical role environmental security plays in overall state security, as well as for our nation, our way of life, and indeed for the human race at large.