On the timescales of sustainability and futurability

Sustainability has a plethora of ambiguous definitions, partly because there are no consistent timescales acceptable to all interested authors. Co-evolutionary processes between the anthroposphere and the biosphere offer an alternative to sustainability and hence the timescales could be examined by a simple systems analysis. We consider a system of anthropospheric food energy demand and entropy production to evaluate the timescales of sustainability at past technological revolutions in the anthroposphere. Our analysis suggests that each of technological revolutionary steps, the Neolithic/Agricultural, Industrial, and Information Revolutions, has forced the sustainability timescale to decrease by an order of 2. However, we suggest that the minimum timescale of the most recent sustainability is 100–400 years, which is longer than that implied by other sustainability indices (∼100 years). The recently emerged concept of ‘futurability’, an ideal form of sustainability, could help seek futurable states of human–environment interactions beyond the next few hundred years.