Sustainability trade-offs and synergies: A comparative environmental policy analysis of emerging and advanced economies

• Identifies trade-offs and synergies in emerging and advanced economies. • Applies a 3C Bayesian methodology: clustering, classification, and causal analysis. • Finds sanitation, water, forest, and climate synergies in emerging economies. • Reveals urban expansion and sanitation trade-offs with biodiversity in developed nations. • Shows biodiversity improves air quality, and pollution control strengthens ecosystems. Achieving environmental sustainability requires balancing policy trade-offs while leveraging synergies to enhance governance effectiveness. This study examines environmental policy interactions in emerging and advanced economies using the 2024 Environmental Performance Index. Applying a 3C analytical framework—clustering (expectation–maximization), classification (Bayesian network with tree-augmented naïve Bayes), and causal analysis (Bayesian structural equation modeling)—the analysis identifies distinct environmental performance profiles and quantifies structural interdependencies among environmental performance categories. Findings reveal that emerging economies exhibit strong environmental synergies: sanitation improvements enhance heavy metal management, water resource availability supports forest ecosystems, forest conservation strengthens water quality, and climate mitigation efforts improve air pollution outcomes. In contrast, advanced economies display a mix of synergies and trade-offs. Biodiversity conservation improves air quality and benefits from effective heavy metal regulation, yet forest management and the expansion of sanitation infrastructure create trade-offs that contribute to biodiversity loss. These results underscore the complexity of sustainability governance and the need for context-specific strategies. Emerging economies should integrate sanitation, water governance, ecosystem management, and climate policy to reinforce mutually beneficial environmental outcomes. Advanced economies must navigate land-use constraints and infrastructure pressures by aligning conservation policies with urban planning and nature-based solutions. By revealing structural interdependencies across environmental dimensions, this study strengthens the methodological foundation for composite-index analysis and offers actionable insights for evidence-based policy design in diverse economic contexts.