This chapter examines the published work and careers of American conservationist William Vogt and Brazilian physician-geographer Josué de Castro during the early Cold War. It emphasizes the different affective strategies that the two men employed to persuade readers of their competing positions regarding the relationship between human population, arable land, food supply, and global security. As a briefly prominent intellectual from the global South, De Castro challenged the emerging, US-led consensus that population control was essential for economic development. Based on his own experiences among marginalized Brazilians, De Castro viewed Vogt’s concern with “carrying capacity” limits as an imperialist imposition on the autonomy of less empowered people. He feared that prioritizing population reduction as the solution to resource scarcity would undermine movements for social and economic transformation, such as agrarian reform in rural Latin America. With little personal experience of the world’s poor, Vogt projected a pessimistic vision of the future on continents overrun by desperate, starving hordes. De Castro’s contrasting vision, on the other hand, stemmed from frequent encounters with the chronically hungry and a more sympathetic understanding of their plight.