Every living system – a living organism, a city, a human body, a region – can be interpreted as the result of the relationship between an energy source and a heat sink: it can only evolve and thrive thanks to continuous inflows of energy and resources from the environment and outflows of heat, emissions, and wastes back into the environment. As such, the sustainability of a system is defined by the way that system uses and exchanges energy and resources. Working towards a one-planet compatible society thus requires full understanding and quantification of the biophysical roots of economic activities. Unfortunately, humanity’s growing metabolism has led the humanity-nature integrated system to shift from an empty- to a full-world over the past few decades (see infographics; adapted from Daly H.E. and Farley J., Ecological Economics. Principles and Applications. Island Press, Washington DC, USA, 2004.)
The sustainability imperative thus provides the opportunity to explore humanity and to study the relations between human beings – their individual and collective expressions such as economies and societies – and the context provided by their natural environment. The study and the pursuit of sustainability, cannot be limited to environmental issues nor reduced to biophysical analyses, and must embrace a systemic thinking in which economic theories must be consistent with biophysical principles as well as with social science theories.