Changes in the environment can impact international relations theory, despite enjoying only a limited amount of attention from scholars of the discipline. The sorts of influence that may be identified include ontology, epistemology, concepts, and methods, all of these being related to varying perspectives on international relations. It is likely that the most profound implications arise at the ontological level, since this establishes assumptions about, for example, whether the world we wish to understand is both political and ecological. However, more recently the recognition of the practical challenge presented by the environment has become widespread, though it has not yet translated into a significant impact on the discipline of international relations, even when theoretical implications are noted. It is now almost obligatory to include the environment in any list of modern international relations concerns, as over time it has become necessary to include peace, underdevelopment, gender, or race, as they quite rightly became recognized as significant aspects of the field. Moreover, the environment, as a relatively novel subject matter, has naturally brought some critique and innovation to the field. However, studies of the environment are also subject to such descriptors as “mainstream” and “radical” in debates about how best to tackle the subject. As is often the case, the debates are sharpest among those with the greatest interest in the subject.