Composite environmental indices-a case of rickety rankings

Abstract

Composite indices have been widely used to rank the environmental performance of nations. Such environmental indices can be useful in communicating complex information as a single value and have the potential to generate political and media awareness of environmental issues. However, poorly constructed, or poorly communicated indices, can hinder efforts to identify environmental failings, and there are considerable differences in rank among existing environmental indices. Here, we provide a review of the conceptual frameworks and methodological choices used for existing environmental indices to enhance our understanding of their accuracy and applicability. In the present study, we review existing global indices according to their conceptual framework (objectives of the index and set of indicators included) and methodological choices made in their construction (e.g., weighting and aggregation). We examine how differences in conceptual frameworks and methodology may yield a more, or less, optimistic view of a country's environment. Our results indicate that (1) multidimensional environmental indices with indicators related to human health and welfare or policy are positively correlated; (2) environment-only indices are positively correlated with one another or are not correlated at all; (3) multidimensional indices and environment-only indices are negatively correlated with each other or are not correlated at all. This indicates that the conceptual frameworks and indicators included may influence a country's rank among different environmental indices. Our results highlight that, when choosing an existing environmental index-or developing a new one-it is important to assess whether the conceptual framework (and associated indicators) and methodological choices are appropriate for the phenomenon being measured and reported on. This is important because the inclusion of confounding indicators in environmental indices may provide a misleading view of the quality of a country's environment.

Keywords: Composite; Environmental; Index; Indices; Ranking.

Figure 1. Diagram depicting the three dimensions of sustainability, adapted from Purvis et al. (2018).

Note: Multidimensional indices include indicators that fall under the environment, society, and economy pillars. Environment-only indices include indicators that only fall under the environment pillar.

Figure 2. Relation between: (A) ranks for New Zealand and Niger, (B) ranks for Germany and Mongolia (relationship break down by category of environmental index).

Note: Abbreviations: Composite Index of Environmental Performance (CIEP); Ecosystem Wellbeing Index (EWI); Ecological Footprint tot al (EF tot); Ecological Footprint per capita (EF pc); Environmental Performance Index (EPI); Environmental State & Sustainability and Index (ESSI); Environmental Vulnerability Index (EVI); Legatum Prosperity Index Natural Environment Pillar (LPI NE).