The interaction mechanism of multi-SDG synergy on SDG 14 in the context of land-sea coordination: A multi-scale analysis

SDG 14 aims to achieve the sustainable development of oceans and seas. However, the mechanisms through which multiple SDGs interact to influence SDG 14 across different spatial scales remain unclear. This study first identifies the five key SDGs (SDGs 6, 8, 9, 11, 12) most closely related to SDG 14, then it employs partial least squares structural equation modelling (PLS-SEM) to analyze the local impact of SDG synergies on SDG 14 in Chinese coastal areas. A spatial econometric model with a land-sea weight matrix further quantifies the cross-border effects of inland SDGs synergies on the performance of coastal SDG 14. We found that in terms of local interaction in coastal areas, economic growth (SDG 8) and sustainable consumption and production (SDG 12) positively impact SDG 14 in coastal areas, with direct effects of 0.55 and 0.422, respectively. In contrast, industrialization and infrastructure (SDG 9) and sustainable cities and communities (SDG 11) exert suppressive effects, with direct impacts of −0.567 and −0.554. It is worth noting that all indirect effects are insignificant, suggesting that SDG synergies in coastal areas have no impact on SDG 14. This is due to the complexity of the interaction pathways, which causes the effects to cancel each other out. At the level of cross-border interaction between land and coastal area, inland SDG synergies generate positive spillover effects on coastal SDG 14, with stronger effects from non-adjacent inland provinces than from adjacent ones. These findings underscore the need for policy interventions to strengthen coordination among the Sustainable Development Goals (SDGs) to avoid offsetting effects; Cross-regional coordination is essential, especially to encourage non-adjacent inland contributions. Overall, the study provides reference insights for China to promote its SDG 14 and the search for land-sea coordination.