The concept of autonomous adaptation is widely used to describe spontaneous acts of reducing risks posed by resource scarcity and, increasingly, climate change. Critics, however, have claimed it is unproven, or simplifies the agency by which smallholders respond to risk. This paper presents empirical research in eight Karen villages in Thailand to identify how resource scarcity is linked to adaptive responses including livelihood diversification. The paper argues that autonomous adaptation is driven by how environmental change and scarcity present livelihood risks, rather than physical risks alone. Adaptation planning therefore should acknowledge different experiences of risk, and socio-economic barriers to adaptation.