William Baxter, from People or Penguins, in May, Applied Ethics, pp. 133-138.

Main thesis: The welfare of animals is entirely dependent on human interests.

(p. 134) Criteria or assumptions:
1. People should be free to do as they wish short of interfering with the interests of other humans.
2. Conservation is necessary since resources can never satisfy the needs of all humans.
3. Every human is deserving of respect and fairness in the application of the community's rules.
4. Every human is entitled to a decent minimum of wealth to avoid permanent privation.
 

            Animals need not be preserved for their own sake: they need to be preserved for the sake of
            humans.             Clean air benefits both humans and animals.             Only humans are capable of asking ought questions.             Pure air is not an appropriate goal; an optimal state of pollution is an appropriate goal.             A balance between an acceptable level of pollution and an desirable level of food, shelter, etc. can
            be struck.

Note: On p. 134, Baxter states a project of ethical theory. If you disagree with his particular judgments on clean air, water, etc., he observes, you may have a more fundamental disagreement. You are likely, for example, to disagree with Baxter's criteria when you disagree with his particular judgments. If you disagree with his particular judgments, Baxter points out, "the task will then be yours to identify the basic set of criteria upon which your particular judgments rest." Baxter here describes an important feature of ethical theory: an invitation to each person to identify and examine the assumptions of his or her judgments.