Ecological Indicators 36 (2014) 508–518 Contents lists available at ScienceDirect Ecological Indicators jo ur nal ho me page: www.elsevier.com/locate/ ecolind Review Theoretical exploration for the combination of the ecological, energy, carbon, and water footprints: Overview of a footprint family Kai Fang ∗ , Reinout Heijungs, Geert R. de Snoo Institute of Environmental Sciences, Faculty of Science, Leiden University, 2333CC Leiden, The Netherlands a r t i c l e i n f o Article history: Received 11 March 2013 Received in revised form 21 August 2013 Accepted 25 August 2013 Keywords: Footprint family Environmental impact assessment Characteristics Performance evaluation Planetary boundaries a b s t r a c t Over the past two decades, a continuously expanding list of footprint-style indicators has been introduced to the scientific community with the aim of raising public awareness of how humanity exerts pressures on the environment. A deeper understanding of the connections and interactions between different foot- prints is required in an attempt to support policy makers in the measurement and choice of environmental impact mitigation strategies. Combining a selection of footprints that address different aspects of envi- ronmental issues into an integrated system is, therefore, a natural step. This paper starts with the idea of developing a footprint family from which most important footprints can be compared and integrated. On the basis of literature review in related fields, the ecological, energy, carbon, and water footprints are employed as selected indicators to define a footprint family. A brief survey is presented to provide background information on each of the footprints with an emphasis on their main characteristics in a comparative sense; that is, the footprints differ in many aspects more than just the impacts they are addressed. This allows the four footprints to be complementarily used in assessing environmental impacts associated with natural resource use and waste discharge. We evaluate the performance of the footprint family in terms of data availability, coverage complementarity, methodological consistency, and pol- icy relevance and propose solutions and suggestions for further improvement. The key conclusions are that the footprint family, which captures a broad spectrum of sustainability issues, is able to offer a more complete picture of environmental complexity for policy makers and, in particular, in national-level stud- ies. The research provides new insights into the distinction between environmental impact assessment and sustainability evaluation, properly serving as a reference for multidisciplinary efforts in estimating planetary boundaries for global sustainability. © 2013 Elsevier Ltd. All rights reserved. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 2. Review of the literature on combining footprint indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 3. Elaboration of a footprint family . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 3.1. Selection of footprint indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 3.2. Survey of selected footprints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 3.2.1. Ecological footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 3.2.2. Energy footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511 3.2.3. Carbon footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511 3.2.4. Water footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511 3.3. Comparison of selected footprints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511 3.3.1. Roots and stressors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511 3.3.2. Components and units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511 3.3.3. Methods and scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512 3.3.4. Other characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513 ∗ Corresponding author. Tel.: +31 71 5271486; fax: +31 71 5277434. E-mail address: fang@cml.leidenuniv.nl (K. Fang). 1470-160X/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ecolind.2013.08.017