Can cities really be sustainable?

Introduction

            There is a twofold reality concerning cities. On the one hand, they are the locus of many of our most well-rehearsed national problems (Amin, Massey & Thrift, 2000), but on the other, they can be considered among the brightest stars in the constellation of human achievement (Rees & Wackernagel, 1996). Therefore, they are sinks of challenges, but also sources of creativity and hope (Amin, Massey & Thrift, 2000).

The nature and variety of challenges which cities have faced during their existence have differed widely. At the very beginning, the first human agglomerations or ‘walled cities’ were shelters against invasion, starvation and wild elements. Then the Greco-Roman cities can be considered the origins of politics, democracy and citizenship but also were centres of slavery and injustice. Much later, the Victorian industrial metropolis was locus of poverty, grime and disease as well as generators of moral revolutions (Amin, 2006). Nowadays cities are recognized as being arenas for social inequalities and major causes of natural resource degradation. Moreover, since the first years of the last century, these problems have been increasing due to the progressive urban population growth. In this sense, according to the last World Urbanization Prospect report, within 40 years almost the 70% of the total population will live in cities (World Urbanization Prospects, 2007). As mentioned by Amin (2006), the human condition has become the urban condition, and hence, the future of mankind is now (more than ever) closely linked to the destiny of our cities.

Pottersville

Pottersville is not the town of the most famous magician of contemporary literature. Pottersville is a dark village, lit only by neon lights and where looting, gambling and drinking reign everywhere. It owes its name to the owner of everything that exists in the city, Henry F. Potter, much like citizen Kane.

This is an alternative Bedford Falls without George Bailey, in the Capra’s film It’s a wonderful life! It is also the favorite example of S. J. Gould in his Wonderful Life to explain the meaning of contingency. In his book, Gould (whom some will remember as the mustache paleontologist that appears in The Simpsons) proposes a new conception of the History of life. On the one hand, he dismisses the traditional iconography and the cone scale, namely evolution as an inexorable progress of increasing complexity, in which the final and inevitable result is the human conscience. By contrast, Gould argues that life we know today is the result of the contingency. If the tape of life could be rewind and modify some variables. Then play it again, the film would be (completely) different.

Emergence: The Connected Lives of Ants, Brains, Cities, and Software

By Steven Johnson

“What ants, neurons, cities and software have in common?”



Steven Johnson (founder of Feed, one of the first online magazines) introduces us in the amazing world of ant colonies, mold, neighbourhoods, neurons and software dynamics.

These communities have the same pattern of behaviour. Every each of them creates an emergence system. Their basic elements act locally, as a result it emerges a global behaviour. The ants of Deborah Gordon do not follow the orders of their queen. They act according to a gradient of pheromones and contacts between other ants. Because of this ants are one of the most successful organisms in the Earth. This pattern appears also in mold aggregations. You can find in the web StarLogo, the software uses to model the complex dynamics of these curious live beings.



Besides ants and molds, Johnson explains that emergence occurs also in human creations as cities and software. He points out the importance of the analysis of Death and Life of Great American Cities written by Jane Jacobs. Her famous “ballet of sidewalks” must be the key factor which a neighbourhood works. The diversity of interactions between neighbours and strangers were the foundations of neighbourhood guilds like Port Santa Maria in Florence. Nowadays these sorts of relationships are becoming extinct because of the appearance of the new edge cities, megalopolis that are created around great malls in the convergence of several highways. The only possible interaction between individuals in these urban systems is by car...



Finally, Emergence shows us the important role of webs as Slashdot.org, Amazon.com or eBay. The first one (created by Rob Malda) is a digital blog of news and comments that are controlled by the own users. They vote positively the best and interesting opinions and vote negatively the worst and spam ones. It sounds like Darwin Natural Selection and is also very similar to the biddings that you can find in eBay. On the other hand, Amazon uses very simple algorithms to join products that the costumer may like (“Costumers who bought that also bought this”). This kind of software is the basis of new routes which are configuring the chaos of Internet. Small actions of each blog writer, costumer or seller create a global pattern just like ants and neighbours do in their colonies and cities.

Urban Growth Patterns

“Are there laws which determine the number, size, and distribution of towns?”

W. CHRISTALLER

MAKSE et al. Developped in the 90s a mathematical model (Correlated Percolation Model) that relates the pysical form of a city and the system within which it exits. This was based on the ideas of percolation theory and they took into account two key points.

First, data on population density of actual urban systems are known to conform to the relation ρ(r)= ρ₀e^-λr where r is the radial distance from the urban core, and λ is the density gradient.

Second, in actual urban systems, the development units are not positioned at random. Rather, there exist correlations arisin from the fact that when a development unit is located in a given place, the probability of adjacent development units increases. The next figure shows a qualitatie comparison between the actual urban data and the proposed model.

In addition to the strongly correlation between the morphology of actual urban areas and the urban systems obtained in our simulation, the dynamics of the model shows a remarkable pattern of decentralization, a phenomena that occurs in most of the cities in the world.

The use of fractal or chaotic models leads us to view cities as self-organized systems by local actions instead of designs for a centralized intelligence. This fact could give us a wide variety of valuable information concerning the way cities grow and change, and more importantly, the way they might be planned and managed.