Transnational climate policy and marine ecological stability: Insights from the Baltic Sea moon jellyfish

Understanding how climate policies influence marine ecosystem stability is critical for advancing sustainability in vulnerable marine environments. We introduce a novel cross-national climate policy strength index and exposure metric, which are integrated with high-resolution remote sensing data on carbon emissions and key marine environmental variables, alongside two decades of Aurelia aurita (moon jellyfish) occurrence records in the Baltic Sea. Leveraging kernel density analysis, piecewise GLM-SEM, and GAMs, we demonstrate that stronger climate policy strength indirectly enhances the stability of jellyfish populations by mitigating carbon emissions and coastal eutrophication. The results provide operational evidence that transnational climate policy can effectively reduce ecological risks and promote resilience in vulnerable coastal ecosystems, offering a transferable framework for climate-ecology assessments in other regions. The findings also emphasize the value of integrating climate policy assessment with ecological monitoring, and underscore the importance of international cooperation on climate action for maintaining the health of marine ecosystems.