By Peter Zibinski

By 2030, it’s expected that more than half of the world’s 9 billion people will live in in an urban area and more than half of the urban areas needed to house these people have yet to be built. Much of this population will occur around megacities – possibly triple the size of, say, Paris or London.

Yet urban pollution is already astronomical. Although cities currently cover roughly 3 percent of the earth’s surface, they are responsible for more than 70 percent of global carbon emissions. Food, water, and all necessary materials must be shipped in, from somewhere outside, to sustain the city, which rarely produces even a fraction of what it consumes. In the face of the environmental crisis, the complex problems that megacities present are a serious threat to the planet’s already strained ecosystems – and simply cannot be ignored.

But if a large portion of the massive urban population could be persuaded to grow most of their food, fashion products themselves instead of buying, and reuse some if not most of their waste material, we would be on our way to remedying the environmental crisis, right?

Not quite. Planning for urban transformation and the development of entirely new cities is a venture into the world of complexity theory and complex adaptive systems. Cities, as professor Luis Bettencourt of the Santa Fe Institute explains, occurred naturally and spontaneously in society wherever there were advantages to sociality on a large scale. “Cities were never formed and have never grown with the objective of saving energy or protecting the environment,” says Bettencourt. Even with increasing trash re-use, urban farming,  and smaller food and sustainability projects, the projected population expansion will require the construction of more urban infrastructure in the next few decades than in the entire history of our species, and it will require us to think more in depth about how we “build” scale.

Cities are so prevalent, and so powerful, and growing so fast because they have distinct spatial and social advantages over more dispersed living arrangements, like a self-sufficient homestead. There are scientific reasons, quantifiable advantages, for urban living arrangements over rural ones and they generally revolve around the concept of scaling. Scaling laws state that cells, organisms, businesses, cities, etc. expand (or contract) in predictable proportions and at calculable rates relative to their initial size. This, in turn, leads to the formation of economies of scale, which are the basis of the advantages to urbanism.

Economies of scale are functional advantages had by larger systems, organizations, or organisms, per measured unit, over their smaller counterparts. Take a large factory and a smaller one, for example. Without much variance in the size of its infrastructure, the larger factory can produce a single unit cheaper and more efficiently than the smaller one. The same rules apply to cities; larger cities require fewer resources and less infrastructure per capita than smaller cities.

As complex urban socioeconomic systems expand, they adhere to established scaling principles and have in the past benefited from economies of scale. In nature, larger networks are less efficient and move more slowly. In the built environment, however, the larger the network, the greater the efficiency,  the greater the speed, and the greater the rate of expansion. And too often the greater the creation of waste.

In the 1800s, planners and theorists characterized the city as a machine, subject to optimization, engineering, and control. This open-ended, informal method of planning and development was the precursor to the conceptualization of the city as an ecosystem, a nervous system, or an organism, concepts that remain popular today. The concept of the city as “alive” is central both to the smart growth and new urbanism movements, but the idea of a city as a life form, in the context of our changing world, may be devastatingly bad. It is no longer hard to imagine an efficient “living” city that supports neither green space nor a diverse population of humans.

“Enabling urban function under economic and technological change, rather than copying form, looms large as a general criticism to some of the simplest applications of New Urbanism,” says Bettencourt , whose research represents a new body of work in geography and complex systems. Using the vast amounts of empirical and quantitative data made available by recent advances in technology and complex mathematics, Bettencourt and his colleagues have been able to measure and compare cities across a variety of social, economic, infrastructural, and spatial factors and offer a new, empirically backed conceptualization of the city.

"A city is first and foremost a social reactor,” says Bettencourt. “It works like a star, attracting people and accelerating social interaction and social outputs in a way that is analogous to how stars compress matter and burn brighter and faster the bigger they are.” In a big city the average citizen owns more, produces more, consumes more and even walks faster than the average resident of a smaller city.

Ultimately, cities balance the creation of larger and denser social webs that encourage people to learn, specialize, and depend on each other in new and deeper ways, with an increase in the extent and quality of infrastructure. Remarkably they do this in such a way that the level of effort each person must make to interact within these growing networks does not need to grow. This new kind of complex urban system grows more intricate than the beehives, coral reefs, and termite nests that it may resemble, and attempting to alter its formation with the goal of sustainability will fundamentally alter the living conditions for better or for worse. Far more data, research, and modeling, is needed to better understand how altering a city’s infrastructural systems and social density will affect quality of life and sustainability within.

Bettencourt’s theory and the new field of quantitative urbanism have exciting implications, but represent only a theoretical first step towards a unified theory of urban living. Even if such a theory or equation were to exist, the challenges facing 21st century citizens, urban or not, will need more than mathematical models. Planners, scientists, and citizens holding out for an “integrated science that is nicely packaged and available to apply immediately will be disappointed,” writes Michael Batty[P3] . “No such package exists, and it probably never will.”

Says Bettencourt, we need to “develop these new ideas to promote types of urban environments that can encourage and nurture the full potential of our social creativity, targeted at sustainable and open-ended human development.”

Ultimately, the task of the planner, the scientist, the citizen, and the activist to transform our cities and cities-to-be remains the same -- to reconceptualize our cities with the goal of creating urban landscapes that can last. If we fail to do this, our policies will kill our cities and our cities will kill the planet.



Bettencourt, L. (2008). The Kind of Problem a City Is. Santa Fe Institute. Retrieved from

Bettencourt, L., & West, G. (2010). A unified theory of urban living. Nature, 467(7318), 912-913.

Bettencourt, L., Lobo, J., Helbing, D., Kuhnert, C., & West, G. (2007). Growth, innovation, scaling, and the pace of life in cities. Proceedings Of The National Academy Of Sciences, 104(17), 7301-7306.

Kane, P. (2016). Savagely malled: Why ‘smart’ cities aren’t so smart. New Scientist. Retrieved 24 October 2016, from

Santa Fe Institute,. (2013). Cities are a new kind of complex system: part star, part network. Retrieved from

Seto, K., Guneralp, B., & Hutyra, L. (2012). Global forecasts of urban expansion to 2030 and direct impacts on biodiversity and carbon pools. Proceedings Of The National Academy Of Sciences, 109(40), 16083-16088.

Peter is a senior integrated marketing communications major and environmental studies minor at Ithaca College. Peter has been passionate about the natural world and our relation to it since an early age and spends much of his free time outside.