Contemporary post-catastrophe fiction typically focuses on a small group of survivors, conveniently getting rid of excess populations by environmental disasters or pandemics. This essay argues that the failure to address the issue of (over)population constitutes an important limitation of these fictions’ capacity to address contemporary social and environmental challenges, as they avoid the question of whether the life forms they imagine are scalable. By situating contemporary post-catastrophe fiction in the longer histories of utopian fiction (which traditionally brackets the problem of scalability), science fiction (where anxieties over over- or depopulation are confronted through the genre’s defining spatiotemporal displacements), and the Victorian novel (which negotiates the pressures that growing populations put on political and aesthetic forms), this essay shows how these fictions engage with the uncertain and contested place of population discourse in contemporary ecological thought.