Leopold''s land ethics thought takes holism as the main construction principle， regards man and nature as a close organic whole， advocates extending the scope of moral care to all beings， and tries to seek the ideal coexistence mode of man and nature. However， because it overemphasizes the priority of the whole and neglects the value of individual existence， it is questioned by some opponents， which makes the development of land ethics in trouble. While inheriting the main idea of Leopold''s land ethics， Callicott deeply thought about the source of his predicament， and put forward two second-order models to defend Leopold''s challenge of "environmental fascism". Callicott took "ecosystem health" as the practical criterion of earth ethics and demonstrated it through "biosphere protection model"， which enriched and developed the land ethics thought. Studying these modern western environmental ethics views is of certain reference significance to China''s current environmental protection and ecological civilization construction.