• In today’s increasingly interconnected world, our recent Nature Communications article (Xiao et al.) aims to explore how domestic attempts to advance the Sustainable Development Goals (SDGs) in a country can have synergistic and/or trade-off effects on the advancement of SDGs in other countries. We proposed a spatial interaction index with a scale of 0 to 100 to quantify the overall magnitude of transboundary SDG interactions. A higher index indicates more substantial transboundary SDG interactions with other countries. The take-home message from this article is that the magnitude of transboundary synergistic effects represented 78.97% of the spatial interaction index and was 3.76 times stronger than the total magnitude of the transboundary trade-off effects. This finding indicated that transboundary SDG interactions between countries can facilitate SDG accomplishment. This also revealed that the overall positive impact of globalisation and openness on advancing global sustainability in an interconnected world. While trade-offs exist in some issues, the predominance of cross-border coordination benefits underscores how collective progress is enhanced through continued cooperation at a global scale. Transboundary SDG interactions are global issues that transcend individual nations. Beyond traditional place-based governance approaches with a focus on a country’s territory, it is significant to adopt a metacoupling-based perspective. This considers each country in the context of its associations with others by identifying, monitoring, and managing areas where key flows originate, progress between borders, and ultimately terminate.

Disproportionate Influence of High-Income Countries on Global Transboundary SDG Interactions

In the article, we examined 768 pairs of SDG indicators to evaluate how an individual SDG indicator of a country interacts with other countries’ indicators. We then analyzed the magnitude of transboundary interactions by income groups. While high-income countries make up only 14% of the global population, they drive over 60% of worldwide transboundary SDG interactions. Despite representing a relatively small fraction of the global population, high income countries are often characterised by robust economies, advanced technologies, and considerable political influence, which may amplify their roles in transboundary SDG interactions, which further affect the achievement of SDGs of other countries. Furthermore, when analysing the components of transboundary SDG interactions, the transboundary synergistic effects/trade-off effects of all high income countries constituted a large percentage of those globally, at 64.95% and 44.06%, respectively.

Synergistic Effects from Nature-Caused Flows Dominate Global Transboundary Interactions Over Those from International Trade

Countries are connected through different transmission channels, and the outcomes of transboundary SDG interactions between countries can vary. Our study classified these channels into two broad categories, each of which interacted with the performance of the SDGs of other countries in different ways: human-caused flows (e.g., international trade) and nature-caused flows (e.g., river flow, ocean currents, and air flow). Compared to the transmission channel via nature-caused flows, transboundary synergistic effects via international trade had a lower share among the countries worldwide. Specifically, the contribution of synergistic effects via nature-caused flows to the total transboundary interactions via nature-caused flows of the countries worldwide reached 90.71%, whereas the contribution of synergistic effects via international trade to the total transboundary interactions via international trade was 73.76%. This also reflects the share of transboundary trade-off effects being higher via international trade, suggesting the complex interactions involved in trading goods and services across borders. While both types of flows can contribute to achieving SDGs across borders, the human-caused flow of international trade requires more careful management to minimize trade-offs and maximize synergistic effects.

Beyond Proximity: Embracing Non-Proximate Transboundary Interactions in Sustainability Research

Tobler’s first law of geography—that everything is related to everything else, but near things are more related than distant ones—serves as a foundational principle in numerous research fields. To revisit and explore Tobler’s first law of geography in the context of SDGs, we analyzed the magnitude difference of transboundary SDG interactions by distance. Results show that the intensity of the transboundary effects of SDG indicators of the countries worldwide differed depending on geographic proximity. Non-neighbouring countries derived more benefits from transboundary interactions facilitated by international trade; however, neighbouring countries derived greater benefits from transboundary interactions via channels of nature-caused flows. Specifically, transboundary synergistic effects via international trade were 14.94% more pronounced with trade partners outside their immediate geographic vicinity than with neighbouring ones. Conversely, nature-caused flows (including rivers, ocean currents, and air flow) resulted in 39.29% stronger transboundary synergistic effects among neighboring countries compared to non-neighboring ones.

The continuing relevance and applicability of this law are evidenced by the broad range of methodologies and concepts that have been developed based on it. In modern times, as sustainability issues increasingly intersect with geographical considerations, there has been an increasing interest in revisiting and further exploring Tobler’s law, especially with respect to SDGs. While the law’s core principle remains valid in many instances, the results of this study suggested that is not applicable in international trade. Due to globalisation, different countries have become more connected and less geographically limited through international trade. Globally, non-neighbouring countries can benefit from comparative advantages by diversifying their traded goods and services, allowing them to interact more with each other than with neighbouring countries. While Tobler’s law remains valuable for understanding influences of nature-caused flows, our research has highlighted the importance of adopting a metacoupling-based perspective. This perspective takes into account a broader array of factors, including those influences that are not in close proximity.