Environmental historians assume that the natural world plays an active role in human history. Conversely, people's actions, and in particular their use of natural resources, have long shaped non-human nature from the smallest ecosystems to the planet as a whole. Moreover, the ways in which people have imagined and understood the natural world—whether through artistic representations or scientific theories—have guided their beliefs about government, society, and economy. Whether they are looking at global politics, individual choices and habits, or the relationship of Americans to their environment, scholars studying environmental history at Northwestern seek to bring non-human nature into human narratives. Historians in this field work with other humanists and social and physical scientists, particularly through the Environmental Policy and Culture Program.