This paper examines the role of systems thinking in environmental(ist) art and activism through a close reading and contextualization of Army Ants: Patterns and Structures (1972), an installation by Alan Sonfist, one of the leading figures in U.S. land art and environmental art of the 1960s and 1970s. It challenges a commonly held retrospective understanding of "environmental art" as being inherently about bringing nature into art (or into the gallery) by showing how important systems thinking, which blurred the natural-cultural divide, was to Sonfist and other artists of the time. It suggests that these two understandings of the environment -- one focused on nature, the other on systems -- were both allied and in tension, and that the unexpected technical problems faced by Army Ants can be attributed at least in part to a failure to acknowledge those tensions. Similarly, the paper suggests, the legacy of glossing over these different understandings of the environment has been at the root of broader conceptual problems with environmental art and activism.