Practitioners of environmental history often turn to the interpretation of material traces to support their arguments about the past. This kind of unwritten evidence-a footprint is a mundane example-signifies a past event by virtue of a causal and/or physical connection with it. Here a series of case studies is used to explore the analogy between environmental historians' interpretation of physical evidence and the interpretive practices of geologists, foresters, archaeologists, forensic scientists and others who also reconstruct the past from similar clues. In thinking about this kind of interpretive work, students of historical methodology have often referred to the historian as a kind of detective or scientist. These two modes of inquiry have different concomitants and consequences. Interpretation is always part of a wider struggle to determine the future. By carefully considering the roles that material traces play in historical consciousness, we are led to a new way of thinking about the possibilities of environmental history.