http://www.econ.vt.edu/tideman/ime.pdf

When human actions cause ecological consequences that harm humans or other species, the propriety of those actions is a moral question. But when, either because of limited resources or because of conflicting purposes, people cannot do all that they wish to protect the environment, then environmental protection is a matter of economics as well as morality.

Harm to humans differs from harm to other species, for three reasons.

• First, we recognize greater obligations to humans than to other species. We recognize obligations to each human individual, while our obligations to other species tend to be seen as obligations to the species as a whole.
• Second, because of the possibility of communication with humans through language, we can have information about the adequacy of compensation to humans in a way not possible when seeking to compensate other species.
• Third, humans are ordinarily concerned with the well-being of other species, not just because other species are required for the advancement of their selfish interests, but also because humans acknowledge an obligation to all species for their own sakes. Thus any harm to other species is a harm to humans as well, while we ordinarily do not think of other species as being harmed by harm to humans.

As beings with awareness of right and wrong, humans have potential moral obligations to all species. There are at least three types of effort to protect other species that a person can make out of his own moral convictions, while asserting at most a minimal right to impose his morality on others. For each type of effort, two levels can be identified:

1. He can adopt personal rules of conduct. He can apply these rules first to his own direct conduct, and then to others, as a condition for cooperating with them, as through trade.

2. He can engage in moral dialogue with others, seeking to persuade them to voluntarily adopt his practices of respect for other species, first with respect to their own conduct, and then as a condition for cooperating with others.

3. He can persuade his community to adopt a standard of behavior that will be required of members of the community. Anyone with a contrary opinion can join another community. In this way, for example, communities outlaw cock fights. Because there are always some costs of relocating, there will be some harm to those who disagree. Such standards are least likely to infringe on the rights of dissenting individuals when they are most local. At the second level, a person can persuade his community to require a standard of behavior of its trading partners. Such action is likely to be most persuasive when the proscribed action is directly related to a traded commodity, as when the Unites States outlawed the importation of tuna caught with nets that killed large numbers of dolphins.

In the absence of perfect universal divine revelation, it is virtually inevitable that people will disagree about the extent of their obligations to other species. Thus, in addition to seeking a common understanding of our obligations to other species, we must seek ways to justly accommodate disagreements about these obligations. This is where theories of economic justice enter.

In addition to the efforts listed above, which a person can pursue on the basis of personal moral conviction, with almost no interference with the rights of others who do not share his moral conviction, a person can also advance a theory of justice that permits him to limit the harm to nature that others cause. In my view, the best basis for claiming a right to limit the harm that others do to nature is a classical liberal theory of justice, similar to that developed by Henry George in Progress and Poverty (1879) or by Bruce Ackerman in Social Justice in the Liberal State (1980). A classical liberal theory of justice recognizes the rights of all persons to equal shares of natural opportunities (that is, everything outside of human beings and the value created by human effort) and the right of each individual to pursue his personal conception of the good. Thus under a classical liberal theory of justice, any individual can assert a right to protect his share of the environment.

The idea that all natural opportunities belong equally to all humanity is a radical idea with profound implications for many areas of human activity, from public finance without coercive taxes to world peace to the meaning of human freedom. The management of the environment under such a liberal theory, with each person potentially having a different conception of the protection that other species deserve, provides a challenge for economic theory but not an insurmountable one.

Consider, for example, the protection of whales. If whales are not persons (which they might become if we found ourselves in moral dialogue with them), then hunting whales may be allowed but limited, either because some humans wish to exercise their rights to nature by protecting whales, or because a reduction in the number of whales impoverishes the world for this generation and for future generations. If the fraction f of the world's population wishes to protect whales, then that fraction of whales is off limits to whale hunters. For the fraction of whales that may be hunted, if hunting causes a loss to other potential hunters in this generation, then those who kill whales should be charged a fee for the economic losses that their behavior causes, with the proceeds shared equally among all potential hunters. If the level of hunting is so great as to cause the number of whales per capita that are available to the next generation of humans to fall below the number available to this generation, then the hunting fee should be the larger of the value of the loss to other potential hunters in this generation and the value of the loss of environmental quality to the next generation.