In response to Callicott's elaboration of the Aldo Leopold land ethic, the land ethic (and, by implication, Callicott's own non-anthropocentric, holistic environmental ethic to the extent that it may differ from Leopold's) has been subject to the charge of “ecofascism,” notably leveled by Tom Regan. If members of overpopulous species, such as deer, ought to be “culled” or “harvested,” in the name of preserving the integrity, stability, and beauty of the biotic community, and if staggeringly overpopulous "Homo sapiens" is also but “a plain member and citizen” of the biotic community, then why should culling and harvesting humans be any less obligatory? In “The Conceptual Foundations of the Land Ethic,” Callicott replies that Leopold presented the land ethic as an “accretion” to our evolving complex "set" of ethics. In other words, the land ethic burdens us with additional moral obligations; it does not substitute for or replace our previously evolved moral obligations, among them the duty to respect the rights of our fellow human beings to life, liberty, and the pursuit of happiness.