In 2008 a historic landmark was crossed, with more than half the world’s population now living in urban centers. Cities have traditionally been — and continue to be — crucibles for creativity, innovation, and wealth; as such, their extraordinary growth is often associated with a rapid rise in living standards, prosperity, and quality of life. Indeed, the more-urbanized countries are, on average, richer, and the world’s two most populous countries, China and India, are undergoing unprecedented experiments in urbanization, mostly as a means of achieving greater wealth.
Analyses of data confirm these trends. Regardless of the indicator, the larger the city, the more innovative the “social capital” it produces. For example, if the size of a city doubles, then, on average, wages, wealth, the number of patents, and the number of educational and research institutions all increase by approximately the same degree, about 15 percent. We refer to this systematic phenomenon as “superlinear scaling”: The bigger the city, the more the average citizen owns, produces, and consumes, whether it’s goods, resources, or ideas. As urban creatures we all participate in this process, manifested in the metropolitan buzz of productivity, speed, and ingenuity.
However, the dark side of urban life manifests an analogous “superlinear” behavior. Doubling the size of a city increases wealth and innovation by about 15 percent, but it also increases the amount of crime, pollution, and disease by roughly the same amount. Apparently, the good and the ugly come hand in glove, an integrated, almost predictable, package. A person drawn to the city by innovation, a greater sense of “action,” and higher wages can also expect to confront an equivalent increase in smog, garbage, theft, stomach flu, and AIDS.
Until the middle of the last century, this dual nature of cities as the origin of wealth and ideas and, at the same time, of pollution and disease was not perceived as a serious threat because cities were still subdominant in terms of population. As cities began to dominate, their entropy production inevitably led to degradation of the environment, severe stresses on resources and energy, and the beginnings of the multiple “sustainability” problems we face in the 21st century. Cities have emerged as the source of the biggest challenges the planet has met since humans became social, yet as reservoirs of creativity and ideas, they are also the source of the solution.
The remarkable and seemingly inextricable linkage between the benefits and costs of community very likely has its origins in the “universal” network structure and group clustering of human interactions: When humans began serious interpersonal interactions about 10,000 years ago, forming sizeable communities, discovering economies of scale and the fruits of “wealth creation,” they brought a fundamentally new dynamic to the planet, a dynamic beyond biology. The resource and energy networks that have evolved to sustain biological organisms and ecosystems are primarily dominated by economies of scale (“sublinear scaling”). The dynamics of such networks constrain the pace of biological life to decrease systematically with increasing size. For example, in comparison with small mammals, big mammals live longer, take longer to mature, and have slower heart rates and cells that work less hard (think mouse versus elephant!).
In contrast, the social networks that underlie the “superlinear scaling” of wealth creation, innovation, crime, and pollution behave in exactly the opposite fashion: The bigger the organization, the faster the pace of life. In big cities, disease spreads more quickly, business is transacted more rapidly, and people walk faster — all in approximately the same systematic, predictable way (the same ~15 percent rule).
Moreover, organisms like mammals stop growing, reaching a roughly fixed size at maturity. Over time scales that are enormous compared with human social time scales, biological systems are relatively stable and sustainable, with major changes taking place over thousands or millions of years. In contrast, in social organizations where growth is driven by superlinear scaling, growth is unbounded, never reaching an “asymptotic” stable state, and proceeding at a rate that is faster than exponential. To sustain such growth in the light of resource limitation requires continuous cycles of paradigm-shifting innovations such as the discovery of iron, steam, computation, and most recently, digital technology. Indeed, the litany of such breakthroughs is testament to the extraordinary ingenuity of the human social mind when it comes to overcoming resource limits. There is, however, a serious catch: Theory dictates that the time between successive innovations must get shorter and shorter. So if we insist on continuous growth driven by wealth creation, not only does the pace of life inevitably quicken, but we must also innovate at a faster and faster rate!
Until recent times the interval between major innovations far exceeded the productive life span of a human being. But this is no longer true: The time between the most recent major shift from computers to IT was only about 20 years and is destined to get even shorter. This pace is surely not sustainable and, if nothing changes, we are heading for a major crash — a potential collapse of the entire socioeconomic fabric. Can we return to an analogue of the sublinear, “biological” phase whence we evolved and its attendant, natural, no-growth, asymptotically stable configuration? Is this even possible? Can we have the kind of vibrant, innovative, creative society driven by ideas and wealth creation as manifested by the best of our world’s cities, or are we destined for a planet of urban slums or the specter raised by McCarthy’s The Road? The challenge is clear: The key to long-term sustainability of the planet lies in applying a scientific lens to cities, with the goal of understanding their dynamic structure, growth, and evolution. — Geoffrey West is a theoretical physicist and former president of the Santa Fe Institute.
Originally published February 2, 2009