Ents, Elves, and Eriador: The Environmental Vision of J.R.R. Tolkien, by Matthew Dickerson and Jonathan Evans. This book is related because it directly addresses Tolkien's use of environmentalism in The Lord of the Rings. This book dissects the different ways that Tolkien is able to address and deal with the issue in the book and helps to clarify what Tolkien's purpose for certain things are.

How the Rich Are Destroying the Earth by Hervé Kemp. This book deals with the issue of constantly taking from the environment for ones own benefit and talks about negative effects of this such as climate change and other issues.

Extra related work: The Lorax, by Dr. Seuss. This book is related to the way environmentalism is discussed in Lord of the Rings because it is ultimately dealing with the same principle of consumerism being a driving force in the destruction of nature. What this book stresses is the importance of conservationism and what are the lasting consequences of not doing this.