While the increasing accessibility of data from scientific studies creates many benefits - and represents a process that should be broadly embraced - in the context of conserving endangered species it can actually be problematic, write David Lindenmayer and Ben Scheele in this Essay. The authors highlight how increasingly, as in other fields experiencing so-called "dual use" dilemmas, researchers who publish on rare species with the goal of aiding conservation inadvertently end up fueling illegal actions - like poaching - that threaten biodiversity. To avoid unknowingly contributing to further species declines, the authors say, biologists must quickly "unlearn" parts of their more than 400-year-old publishing culture - for example, by reevaluating the benefits of publishing rare and endangered species' location data. Lindenmayer et al. acknowledge that restricting information in this way is not without its costs; but, they say, these costs must be weighed against the increasing harm that can result from information being openly available. The authors discuss how such tradeoffs are being evaluated in other fields of science, where dual use is also a concern. Fields such as paleontology and archeology have long maintained restrictions on the publication of site locations, for example, and promoted government regulations to limit collection and trade in fossils and artifacts. Lindenmayer and Scheele briefly outline novel publication strategies that will allow for better protection of endangered species - including, for example, buffering spatial data to provide only very broad location coordinates.