When heritage becomes a burden: an evidence-based reference class of tourism stress in historic cities

Overtourism and carrying-capacity models have traditionally explained heritage-city stress through visitor volume and density. However, these approaches provide limited explanation of why comparable tourism pressures produce different forms and levels of stress across historic cities. This study addresses this gap by examining heritage stress as a perception-driven, context-dependent process shaped by interactions among spatial, social, infrastructural, cultural, and governance conditions. A hybrid review methodology integrating a Scoping Review, Systematic Literature Review, and Realist Synthesis is used to connect conceptual framings, empirical indicators, and Context–Mechanism–Outcome configurations. The findings indicate that mobility conflict, sensory overload, cultural mismatch, short-term rental-induced housing pressure, event-related surges, and commercialisation can operate as interacting mechanisms, with their effects conditioned by urban morphology, governance capacity, temporal concentration, and socio-spatial structure. The study therefore develops an Integrated Reference Class Diagnostic and Intervention Matrix (IRCDI) that supports comparison among heritage-city settings with similar contextual and mechanistic conditions and helps identify context-appropriate intervention priorities. The framework extends volume-based approaches by providing a mechanism-oriented basis for interpreting emerging stress and informing anticipatory governance in historic cities.