Cultural landscapes and their social–ecological values are threatened by changing lifestyles, policies and land-use practices, making their appropriate management a key sustainability challenge. Drawing on five years of interdisciplinary research in Transylvania, we conceptualise the notion of a ‘landscape interface’ – the intersection between the ecological and social subsystems, which through time, shapes and is shaped by the local value system. The landscape interface is a source of system continuity and stability. In Transylvania, many locals still act according to the value system associated with a disappearing landscape interface, a phenomenon we term a ‘value change debt.’ We argue that the erosion of the old value system, together with the weakening of the landscape interface, threatens sustainability – whereas reconnecting social–ecological feedback and thus strengthening the landscape interface could foster sustainability. The new conceptual perspective proposed here could foster greater understanding of cultural landscapes, including the social dimension of human–environment interactions.