The global sustainability challenge facing us is simply stated: it combines an empirical

assessment and a normative claim. The evidence-based assessment, as shared by

numerous scientists, is that current society-nature interactions are not sustainable –

they are negatively affecting both vital ecological systems and human welfare in ways

that threaten irreversible, long-term damage (UNEP, 2007). Attached to this empirical

claim is the normative position of sustainable development; that societal development

paths should meet fundamental human needs, within and between generations, while

maintaining the planet’s life-support system and conserving living resources.