Validating the nature relatedness scale for environmental and sustainability education: Philippine evidence for factorial, cross-linguistic, and temporal invariance

Human-nature connection is a core learning outcome in environmental and sustainability education (ESE), yet most measurement evidence is Western, limiting comparability for curricula and evaluation in the Global South. We examined the six-item Nature Relatedness Scale (NR-6) for Philippine ESE across three independent samples (n = 266; 326; 230), which involved two cohorts of tertiary learners and one adult community sample, and two languages (English, Filipino). Confirmatory factor analyses supported a theory-guided, modified one-factor solution, indicating essential unidimensionality suitable for brief classroom and field assessments. Multigroup models demonstrated configural and metric cross-linguistic invariance between English and Filipino forms, establishing linguistic equivalence for mixed-language delivery and program comparisons. Critically, the Filipino form showed configural and metric temporal invariance over two weeks, evidencing structural stability across measurement occasions and supporting defensible pre-post tracking in courses and outreach programs. This study offers the first integrated factorial, cross-linguistic, and temporal evidence for the NR-6 in a non-Western, climate-vulnerable setting. Findings position the NR-6 as a practical ESE indicator for monitoring change, comparing language groups on associations with attitudes/behaviors, and evaluating interventions that aim to strengthen human-nature connection, thereby expanding the global evidence base for robust, equity-aware assessment in environmental education.