However, current applications of AESA are based on direct downscaling from the global scale and often ignore regional data. This can lead to inaccurate assessments and ineffective solutions at the local level. To address this, we applied the Techno-ecological synergy (TES) based AESA metric[4] that considers ecosystem services from global to local scales to determine metrics that are more science-based and less subjective. In this work, we implemented it on a national scale for about 180 countries. This results in a novel insight into the absolute environmental sustainability of the nations and demonstrates the pros and cons of AES metrics based on direct downscaling of Planetary Boundaries versus metrics based on knowledge about ecosystem services at multiple scales. Seven sharing principles[5] are applied, including population, gross domestic value (GDP), current carbon dioxide emissions, land area, energy consumption, human development index (HDI), and carbon sequestration rate. These parameters are chosen to represent different dimensions of responsibility and capacity. We calculated and compared the transgression levels (TLs) of all countries studied using the direct downscaling and TES-based metrics, highlighting the differences in sustainability outcomes under each approach. We performed data analysis between the sharing principles, between two different approaches, and between different countries, gaining insights on the relationship between them and the reasons behind the results.
Nine planetary boundaries (PBs)[6] have been defined to represent key earth system thresholds that are essential to maintain a stable and safe operating space without causing irreversible environmental change. In this framework, a quantitative boundary for each earth process is defined as the ecological limit. AESA based on planetary boundaries assumes that earth's ecological supply is globally accessible and can be equally allocated across all regions. However, this assumption is not accurate, as many ecological services -- such as carbon sequestration -- are regional and often serve as private or localized resources. Such assessments offer only a coarse global overview and fail to provide practical insights at smaller spatial scales. Additionally, they do not motivate ecosystem restoration, as responsibility is distributed globally without accounting for regional ecological capacity. The metric used in this work allocates private supply to private use, thereby generating results that better reflect regional conditions and ecological characteristics.
Results at the method level indicate that the direct downscaling approach tends to underestimate transgression levels. For five out of seven sharing principles, over 50% of the countries studied have higher transgression levels when assessed using the TES-based AESA metric. We analyzed the common characteristics of the countries whose TLs are underestimated by direct downscaling and found that nations with smaller land area and lower local carbon sequestration capacity are most affected. At the sharing principle level, several parameters show strong positive correlations: energy consumption and GHG emissions, land area and carbon sequestration rate, energy consumption and GDP, as well as GHG emissions and GDP. At the national level, a few countries consistently show high transgression levels across methods and sharing principles, including China, the United States, India, several North African countries, and some Southwest Asian countries. These findings highlight the importance of incorporating regional ecological conditions and differentiated responsibilities into sustainability assessments. By aligning transgression assessments with regional conditions, decision-makers can better prioritize actions and design policies that reflect both local capacities and global responsibilities.
This approach offers deeper insights into how allocation choices influence sustainability outcomes and highlights the importance of science-based regional data in absolute environmental sustainability assessments. One direction for future work is to expand the scope beyond carbon emissions by including additional planetary boundaries such as freshwater use and biodiversity loss, as well as exploring more sharing principles. Another extension is to integrate social and justice perspectives into the metrics at multiscale. Additionally, dynamic temporal models could be developed to incorporate emission trends and ecosystem restoration over time, leading to more adaptive sustainability assessments.
Reference
[1] NASA/GISS, “NASA’s Goddard Institute for Space Studies (GISS).”
[2] J. B. Guinée, A. De Koning, and R. Heijungs, “Life cycle assessment‐based Absolute Environmental Sustainability Assessment is also relative,” J of Industrial Ecology, vol. 26, no. 3, pp. 673–682, Jun. 2022, doi: 10.1111/jiec.13260.
[3] V. Tulus, J. Pérez-Ramírez, and G. Guillén-Gosálbez, “Planetary metrics for the absolute environmental sustainability assessment of chemicals,” Green Chem., vol. 23, no. 24, pp. 9881–9893, 2021, doi: 10.1039/D1GC02623B.
[4] Y. Xue and B. R. Bakshi, “Metrics for a nature-positive world: A multiscale approach for absolute environmental sustainability assessment,” Science of The Total Environment, vol. 846, p. 157373, Nov. 2022, doi: 10.1016/j.scitotenv.2022.157373.
[5] X. Bai et al., “Translating Earth system boundaries for cities and businesses,” Nat Sustain, vol. 7, no. 2, pp. 108–119, Jan. 2024, doi: 10.1038/s41893-023-01255-w.
[6] W. Steffen et al., “Planetary boundaries: Guiding human development on a changing planet,” Science, vol. 347, no. 6223, p. 1259855, Feb. 2015, doi: 10.1126/science.1259855.