Countries still lack adequate metrics to monitor environmental sustainability across a range of relevant environmental and resource issues. The Strong Environmental Sustainability Index (SESI) is intended to fill this gap. SESI is the result of aggregating 21 indicators across different dimensions. Each of the underlying indicators is related to the functions of natural capital and normalized using science-based targets. It uses the geometric mean to aggregate in order to reflect the limited substitutability between the functions of natural capital.
This paper analyses the use of SESI to monitor environmental sustainability. The results of the index, which is computed for 28 European countries, show that several functions of natural capital are impaired in Europe. Countries tend to perform worse in indicators related to pollution and ecosystem health, compared to indicators that describe the provision of natural resources, and human health and welfare.
As the results are sensitive to assumptions in the normalization, weighting and aggregation processes, the relevant choices have been aligned with the theoretical underpinnings of the Environmental Sustainability Gap (ESGAP) framework. SESI responds to the demands of the "Beyond GDP" community on the need for a single environmental sustainability metric that can complement GDP in its (mis-)use as a headline indicator for development.