Just like biological organisms, cities follow simple physical laws in their growth. These are the findings of research conducted by theoretical physicist Geoffrey West and his team at the Santa Fé Institute. In their paper Growth, innovation, scaling, and the pace of life in cities they compare vast data of city growth across the globe using techniques usually employed in fields like biology and physics and come up with some surprisingly simple maths: as cities scale up, the quantities reflecting wealth creation and innovation have 1.2 >1 (increasing returns), whereas those accounting for infrastructure display 0.8<1 (economies of scale). In other words: As city population grows with another member, what is needed to support that growth is only 0.8 more infrastructure (gas stations, schools, electrical cable, etc) whereas that same member creates an output of 1.2 in growth (from wages to patent production, AIDS rates to the speed of walking, etc).
So, opposed to biological organisms who’s metabolism slows down with increasing size, the metabolic rate of the city i.e. the pace of its social life increases superexponentially (above the exponential) with it’s size. However, growth is constrained by the availability of resources and their rates of consumption. Therefore an organism can only grow to a certain size before stagnating. Sublinear (below the exponential) growth as that of a biological organism will subsequently stagnate at the carrying capacity. But when growth is superlinear as in the wealth and innovation creation of cities, the equation changes drastically as the growth rate is unbounded. But as resources are limited, unlimited growth is ultimately unsustainable. That means that as population grows innovation cycles must be generated at a continually accelerating rate, to sustain growth and avoid stagnation or collapse. Each time a new cycle is initiated the city continues to grow but with a new set parameters and conditions. This process can continually be repeated, so pushing the potential collapse into the future. Unfortunately the time between cycles decrease with the growth of the population, forcing ever faster innovation in order to continue sustaining the city.
Here it is quite interesting to note the parallels to Marco Casagrande’s theory of Urban Acupuncture which is based on viewing the city as a living organism and how West and Casagrande arrive at this similar conclusion from entirely different approaches.
Based on his findings West suggest a science of cities providing a set of predictive tools which can be applied when setting targets for local policy. Furthermore deviations from these predictions can provide more accurate measures of the successes and failures of local factors (including policy) in shaping specific cities, thus assisting the transit into a future where our social forces and living standards are compatible with the preservation of the planet’s resources.
In an interview at the Edge West explains further, that we as social human beings need to realize our own mortality as well as the holistic integration of the different areas of concerns we as a species have, the financial markets, polution, global warming, health, and so on, and that focusing on these areas separately yield potential dangers: As they are interrelated changes made in one area could have unintended consequences. In order to understand their interrelatedness we need a unified theory of sustainability and calls for a unified theory of sustainability, a framework where their interrelatedness becomes apparent and we can relate them back to social organization and dynamics.