In environmental philosophy, environmental ethics is an established field of practical philosophy "which reconstructs the essential types of argumentation that can be made for protecting natural entities and the sustainable use of natural resources." The main competing paradigms are anthropocentrism, physiocentrism (called ecocentrism as well), and theocentrism. Environmental ethics exerts influence on a large range of disciplines including environmental law, environmental sociology, ecotheology, ecological economics, ecology and environmental geography.
There are many ethical decisions that human beings make with respect to the environment. These decision raise numerous questions. For example:
Should humans continue to clear cut forests for the sake of human consumption? Why should humans continue to propagate its species, and life itself? Should humans continue to make gasoline-powered vehicles? What environmental obligations do humans need to keep for future generations? Is it right for humans to knowingly cause the extinction of a species for the convenience of humanity? How should humans best use and conserve the space environment to secure and expand life? What role can Planetary Boundaries play in reshaping the human-earth relationship?
The academic field of environmental ethics grew up in response to the works of Rachel Carson and Murray Bookchin and events such as the first Earth Day in 1970, when environmentalists started urging philosophers to consider the philosophical aspects of environmental problems. Two papers published in Science had a crucial impact: Lynn White's "The Historical Roots of our Ecologic Crisis" (March 1967) and Garrett Hardin's "The Tragedy of the Commons" (December 1968). Also influential was Garett Hardin's later essay called "Exploring New Ethics for Survival", as well as an essay by Aldo Leopold in his A Sand County Almanac, called "The Land Ethic", in which Leopold explicitly claimed that the roots of the ecological crisis were philosophical (1949).
The first international academic journals in this field emerged from North America in the late 1970s and early 1980s – the US-based journal Environmental Ethics in 1979 and the Canadian-based journal The Trumpeter: Journal of Ecosophy in 1983. The first British based journal of this kind, Environmental Values, was launched in 1992.
Marshall's categories
Some scholars have tried to categorise the various ways the natural environment is valued. Alan Marshall and Michael Smith are two examples of this, as cited by Peter Vardy in The Puzzle of Ethics. According to Marshall, three general ethical approaches have emerged over the last 40 years: Libertarian Extension, the Ecologic Extension, and Conservation Ethics.
Libertarian extension
Marshall's libertarian extension echoes a civil liberty approach (i.e. a commitment to extending equal rights to all members of a community). In environmentalism, the community is generally thought to consist of non-humans as well as humans.
Andrew Brennan was an advocate of ecologic humanism (eco-humanism), the argument that all ontological entities, animate and inanimate, can be given ethical worth purely on the basis that they exist. The work of Arne Næss and his collaborator Sessions also falls under the libertarian extension, although they preferred the term "deep ecology". Deep ecology is the argument for the intrinsic value or inherent worth of the environment – the view that it is valuable in itself. Their argument falls under both the libertarian extension and the ecologic extension.
Peter Singer's work can be categorized under Marshall's 'libertarian extension'. He reasoned that the "expanding circle of moral worth" should be redrawn to include the rights of non-human animals, and to not do so would be guilty of speciesism. Singer found it difficult to accept the argument from intrinsic worth of a-biotic or "non-sentient" (non-conscious) entities, and concluded in his first edition of "Practical Ethics" that they should not be included in the expanding circle of moral worth. This approach is essentially then, bio-centric. However, in a later edition of Practical Ethics after the work of Næss and Sessions, Singer admits that, although unconvinced by deep ecology, the argument from intrinsic value of non-sentient entities is plausible, but at best problematic. Singer advocated a humanist ethics.