Linking absolute environmental sustainability assessments to the sustainability transition of local policies: a case study of the Metropolis of Lyon
Résumé
Local policies guiding sustainability transition uses targets. To be science-based, their definition can follow the principles of Absolute Environmental Sustainability Assessment. A way to define them is to use Planetary Boundaries (PB) translation methods, as they provide a systemic assessment of the environmental carrying capacities affected by a given territory. We reviewed 75 academic and non-academic publications that have carried out PB translations at the territorial level. Most of these publications aimed to guide local sustainability transitions. Yet, they did not systematically use absolute targets resting on environmental carrying capacities but rather privileged objectives originating from institutions. This may be because PB were not designed to be used operationally as local science-based targets, unlike Earth System Boundaries (ESB) framework, which aims to set operational science-based targets for local policies. There is a need to test the operationality of ESB indicators at local level. However, we have not yet identified any ESB translations in the review. In collaboration with the Metropolis of Lyon, we have tested a translation of 4 ESB indicators at the level of the metropolis of Lyon to assess impacts on climate change, biosphere functional integrity, water flows and nutrient cycles. It validates that ESB translations can set local science-based targets, some of which can be used as such, like the minimum ecosystem area to maintain functionality, or translated into pressures allocated to territories, such as the 1.5°C climate target. However, a limitation is that some of the indicators provided are not currently usable in a consumption-based analysis. We also tested that this ESB translation can enrich planning documents and local policies, especially those related to land use and climate change commitments. This analysis shows the potential and improvements needed for ESB translations to set operational, science-based targets for local policies.