A system of environmental ethics recently developed by Lawrence Johnson may be used to analyze the moral implications of biological control. According to this system, entities are morally relevant when they possess well-being interests (i.e., functions or processes that can be better or worse in so far as the entity is concerned). In this formulation of ethical analysis, species and ecosystems are morally relevant because they are not simply aggregates of individuals, so their processes, properties, and well-being interests are not (...) reducible to the sum of their individual members. Following Johnson's thesis, species and ecosystems have morally relevant interests in surviving and maintaining themselves as integrated wholes with particular self-identities. This theoretical structure gives rise to a number of ethical criteria that are particularly relevant to biological control, which apply to the ecosystem (the extent to which it is large, native, unique, and integrated) and to the action being considered (the extent to which it is novel, omnipresent, monitored, reversible, and necessary). In these terms, it is evident that not all biological control efforts are ethically defensible. In general terms, natural biological control is most desirable, followed by augmentative strategies, classical approaches, and finally neoclassical biological control. Two specific cases (neoclassical biological control of rangeland grasshoppers and classical biological control of prickly pear cactus) illustrate the ethical concerns. Finally, it can be shown that formalized restrictions of biological control are necessary, given the unique properties of this technology. (shrink)