William Rees is a human ecologist, ecological economist, Professor and former Director of the University of British Columbia’s School of Community and Regional Planning in Vancouver, Canada. His research and teaching focus on the biophysical prerequisites for sustainability in an era of accelerating ecological change. Within this ‘envelope’, has a special interest in ecologically-relevant metrics of sustainability and their interpretation in terms of behavioural ecology and complexity theory. He is perhaps best known in ecological economics as the originator and co-developer of ‘ecological footprint analysis’. His book on eco-footprinting, with then PhD student Dr Mathis Wackernagel, has been translated into eight languages including Chinese. Widely (and controversially) adopted for sustainability assessments by Governments, NGOs and academics, the human ‘eco-footprint’ has arguably become world’s best-known sustainability indicator. Prof Rees has also authored over 130 peer reviewed papers and book chapters and numerous popular articles on humanity’s (un)sustainability conundrum. He is a long-term member of the Global Ecological Integrity Group, a Fellow of the Post-Carbon Institute, a founding member and past President of the Canadian Society for Ecological Economics and founding Director of the OneEarth Initiative. The influence of Dr Rees’ work is widely recognized and awarded. He has lectured by invitation throughout North America and 25 other countries around the world; the Vancouver Sun named Prof Rees one of British Columbia’s top public intellectuals in 2000; in 2006 he was elected to the Royal Society of Canada and in 2007 he was awarded a prestigious Trudeau Foundation Fellowship.