There is no universally accepted definition of sustainability. Values and political and economic interests play a central role in the sustainability debate. From the scientific point of view, however, certain approaches provide comparison tools among countries that record a path towards sustainability progress.

An outline of these approaches follows:

Pressure-State-Response (PSR)

This model was developed by the Organization for Economic Co-operation and Development (OECD, 1991) and is based on the fact that humans exert pressures on the ecosystem and the society which alter their state and call for certain responses. Its primary focus is on ecological aspects although socio-economic indicators are also of interest.

Ecological Footprint

It was introduced in Rees (1992) and calculates the equivalent land needed to produce certain basic resources and absorb certain wastes associated with a given population. In short, the ecological footprint is the productive land that a population uses. It is biased towards the ecological side and computes a land area, not a sustainability score.

Barometer of Sustainability

This model was introduced by the International Union for the Conservation of Nature (IUCN) (Prescott-Allen, 2001) and is a visual tool of sustainability assessment. The sustainability of a country has two fundamental components, Ecosystem Well-Being and Human Well-Being. All indicators are scaled in [0, 100], where 0 is the worst performance and 100 the best performance of an indicator. Then scores are computed by a straightforward aggregation.

Environmental Sustainability Index (ESI)

ESI (Esty et al., 2005) computes an environmental sustainability index for a country based on 21 indicators, which in turn are assessed from 76 data sets. The ESI index is computed as a weighted average of indicators with equal weights. Countries are ranked accordingly.

Sustainability Assessment by Fuzzy Evaluation (SAFE)

This model was introduced in Phillis and Andriantiatsaholiniaina (2001) and developed further in Andriantiatsaholiniaina et al. (2004), Kouloumpis et al. (2008), and Phillis and Kouikoglou (2009). SAFE is a hierarchical fuzzy inference system. It uses knowledge encoded into “if-then” rules and fuzzy logic to combine 75 inputs, called basic indicators, into more composite variables describing various environmental and societal aspects and, finally, provides an overall sustainability index in [0, 1].

Multiple Criteria and Fuzzy Logic

A model similar to ESI using 74 indicators and multiple-criteria decision-making (MCDM) in conjunction with a fuzzy inference scheme similar to SAFE was introduced in Liu (2007). It computes an aggregate sustainability index through sequential fuzzy reasoning while MCDM has three steps, decomposition, weighting, and synthesis.

Sustainable Society Index (SSI)

The SSI (Van de Kerk and Manuel, 2008) is based on 22 environmental and societal indicators that are aggregated into 5 main categories using equal weights. The 5 categories are then aggregated into SSI using unequal weights. In all 150 countries are ranked accordingly.

References

• Andriantiatsaholiniaina LA, Kouikoglou VS, Phillis YA (2004) Evaluating strategies for sustainable development: Fuzzy logic reasoning and sensitivity analysis, Ecological Economics 48 (2), 149–172.
• Esty DC, Levy M, Srebotnjak T, Sherbinin A (2005) 2005 Environmental sustainability index: Benchmarking national environmental stewardship, Yale Center for Environmental Law & Policy, New Haven, CT.
• Kouloumpis VD, Kouikoglou VS, Phillis YA (2008) Sustainability assessment of nations and related decision making using fuzzy logic, IEEE Systems Journal 2 (2), 224–236.
• Liu KFR (2007) Evaluating environmental sustainability: An integration of multiple-criteria decision-making and fuzzy logic, Environmental Management 39 (5), 721–736.
• OECD (1991) Environmental indicators: A preliminary set, OECD, Paris.
• Phillis YA, Andriantiatsaholiniaina LA (2001) Sustainability: An ill-defined concept and its assessment using fuzzy logic, Ecological Economics 37 (3), 435–456.
• Phillis YA, Kouikoglou VS (2009) Fuzzy measurement of sustainability, Nova Science Publishers, New York.
• Prescott-Allen R (2001) The well-being of nations, Island Press, Washington, DC.
• Rees WE (1992) Ecological footprints and appropriated carrying capacity: What urban economics leaves out, Environment and Urbanization 4 (2), 121–130.
• Van de Kerk G, Manuel A (2008) Comprehensive index for a sustainable society: The SSI - The Sustainable Society Index, Ecological Economics 66 (2–3), 228–242.