Indonesia’s forests are amongst the world’s most biodiverse; they provide critical climate benefits and support human well-being. Yet Indonesia has one of the highest rates of forest loss globally. Much of Sumatra’s remaining tropical forest only exists within protected areas, which are increasingly threatened by small-scale land clearance. Using a case study from Gunung Leuser National Park, we combine factorial survey experiments with semi-structured interviews to examine the effect of four factors on peoples’ decisions to clear protected forest. We found water availability had the strongest effect on clearance; when water was scarce, intention to clear declined. Access to land titles, needing to meet basic needs, and the behavior of others positively influenced intention to clear protected forest. Importantly, how people view land ownership has changed, with an increased desire to obtain official titles to provide land security. We provide useful insights for conservation policy, practice, and protected area authorities. © 2025 The Author(s). Published with license by Taylor & Francis Group, LLC.