Metrics for a nature-positive world: A multiscale approach for absolute environmental sustainability assessment

Abstract

Absolute environmental sustainability (AES) metrics include nature's carrying capacity as a reference to provide insight into the extent to which human activities exceed ecosystem limits, and to encourage actions toward restoration and protection of nature. Existing methods for determining AES metrics rely on the frameworks of Planetary boundaries (PB) and Ecosystem Services. This work provides new insight into the relationship between these methods and demonstrates that AES metrics based on the framework of techno-ecological synergy (TES) are better suited to encouraging nature-positive decisions. PB-based AES metrics downscale planetary boundaries or upscale local ecosystem services, but they partition available services among all users across the planet and make limited use of biophysical information. In contrast, TES-based metrics follow a multiscale approach that accounts for local ecosystem services estimated by biophysical data and models, and combine them with downscaled services from multiple coarser scales. These metrics can provide credit to stakeholders for local ecosystem services, thus encouraging ecosystem protection and restoration. Generally, the PB framework focuses on processes of global importance which currently include nine planetary boundaries that are critical for global stability. The TES framework considers ecosystem services from local to global scales and can be used for determining absolute environmental sustainability precisely at any spatial scale. Theoretical analysis shows that TES-based metrics are more general and can be specialized to PB-based metrics under certain conditions. Through case studies at multiple spatial scales and for various ecosystem services, we show that TES-based metrics are more robust, less subjective, and better suited for encouraging transformation to a nature-positive world.