  A further practical issue which Sylvan sees as requiring theoretical justification is predation: the killing of animals for food. “The vegetarian options face, it certainly seems, insuperable difficulties, especially concerning such issues as animal predation (which is an important, immensely frequent, and often desirable, ecological fact), and concerning the reduction in numbers of animals, especially introduced animals, which build up to ‘pest proportions’ (some reduction is often required for vegetable growing to operate successfully)” (Routley 1982, 5). Sylvan himself, for example, culled feral rabbits (a damaging, introduced species in Australia) and he consumed the animals killed. While his environmental ethic demands respect for intrinsically valuable non-humans, he argues that the