Holmes Ralston III. 2011. A New Environmental Ethics: The Next Millennium for Life on Earth. London, UK: Routledge.
A good overview by a philosopher who pioneered in the area.
Sharpe V, Norton BG, Donnelley S, eds. 2000. Wolves and Human Communities: Biology, Politics, and Ethics. Washington, DC: Island Press.
Addresses the many complex issues that will face societies if they decide to rewild.
Singer P. 2009. The Life You Can Save: How to Do Your Part to End World Poverty. Melbourne, Australia: Text.
Ehrlich PR. 2009. Ecoethics: Now central to all ethics. Journal of Bioethical Inquiry 6: 417-436.
Shifts bioethics away from disproportionate emphasis on medical ethics.