This article argues that understanding "wild" land as terra nullius ("land belonging to no one") emerged during historical colonialism, entered international law, and became entrenched in national constitutions and cultural mores around the world. This has perpetuated an unsustainable and unjust human relationship to land no longer tenable in the post-Lockean era of land scarcity and ecological degradation. Environmental conservation, by valuing wild lands, challenges the terra nullius assumption of the vulnerability of unused lands to encroachment, while indigenous groups reasserting their rights to communal territories likewise contest individual property rights. South American case studies illustrate routinized terra nullius prejudices.