A systematic review of environmental identity: Definitions, measurement tools, and future directions

Environmental Identity (EI) plays a central role in shaping pro-environmental attitudes and behaviors, yet its conceptual complexity and multidimensional nature present challenges for consistent measurement. This systematic review examines the quality and psychometric soundness of instruments designed to assess EI in adults, with particular attention to how well they capture its theoretical complexity. Following PRISMA-COSMIN guidelines, we searched PubMed, Web of Science, and Scopus for empirical studies published in English between 2000 and 2024. Methodological quality was evaluated using the COSMIN Risk of Bias checklist, and the strength of psychometric evidence was rated across studies. Twenty-one studies met inclusion criteria. The original 24-item Environmental Identity Scale (EID) and its shortened or adapted versions were the most frequently used tools. Internal consistency was consistently high, and construct validity was generally supported through hypothesis testing with related constructs. However, structural validity showed inconsistencies, with several studies lacking confirmatory factor analysis or relying solely on exploratory methods. Test–retest reliability and measurement invariance were rarely assessed. Content validity and translation procedures were often underreported or unclear, limiting interpretability across contexts. Overall, existing EI measures demonstrate strong internal coherence but fall short in capturing the construct's full dimensionality. Findings underscore the need for instruments that better reflect the psychological, emotional, behavioral, and sociocultural dimensions of EI. Future research should prioritize improved methodological transparency, longitudinal validation, and the integration of both explicit and implicit measurement approaches.