Sunday, October 11, 2009


Citizenship is a condition of civic equality. It consists of membership of a political community where all citizens can determine the terms of social cooperation on a equal basis. This status not only secures equal rights to the enjoyment of the collective goods provided by the political association but also involves equal duties to promote and sustain then - including the good of democratic citizenship itself.

CITIZENSHIP A Very Short Introduction

Wednesday, October 7, 2009

Saturday, October 3, 2009


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.

Thursday, September 24, 2009

Niches and Invaders

A niche is a term describing the functional position of a species in its ecosystem. In nature there are predators and preys, generalist and specialist species, key species and so on. An invasive species is an exotic species that adversely affect the habitats they invade economically, environmentally or/and ecologically. Here you can find a good example in São Miguel Island (the Açores, Portugal).

On the other hand, on both sides of the commercial streets of most occidental cities, there are plenty of different niches. There is a niche filled by big book stores like Borders (US), Waterstones (UK) or La Casa del Libro (Spain). But it is possible as well observe McDonalds, IKEA or Zara everywhere. Because of Globalization, these sort of stores and restaurants are invading our urban ecosystems.

Friday, September 18, 2009

Complexity Theories of Cities Have Come on Age

International Conference


1. Achievements, criticism and potentials yet to be realized
2. Implications to planning and urban design

TU Delft, September 25 - 27, 2009

Three decades of research have established the field of complexity theories of cities (CTC) as a dominant approach to cities with urban simulation models (USM) as its major methodological tool. Now that the field has come of age, it is time to stop for a moment, look back at what has been achieved, with appreciation, but also with sober criticism and then look forward at potentials that have yet to be realized.

Wednesday, September 16, 2009


Cities are population aggregates that do not produce for themselves the means of subsistence. From their origins, the existence of cities is based on a technical, social and spatial division of production and involves exchanges of various kinds between those who produce subsistence and those who produce manufactured goods, symbolic goods, power and protection. Urbanization dynamics is linked to the potential interaction offered by cities, its urbanity, ie the power that produces the grouping of large number of people in the same place.

Les nouveaux principes de l'urbanisme. La fin des villes n'est pas à l'ordre du jour

Monday, September 7, 2009


James Lovelock and Andrew Watson published a short paper in 1983 to ilustrate a simple example of how the Gaia hypothesis works. This was based in a world with the following characteristics:
  • The model simulates a planet that is orbiting a sun whose radiant energy is slowly increasing (just like the Sun and the Earth). The planet’s soil is 5º C.
  • The world is seeded with two types of daisies: black and white. The black ones have an albedo of 0.25 (absorb light) and the white ones, on the other hand, 0.75 (reflect light).
  • Both flowers can live in a range of temperature (between 5º and 40º C), and their optimal point is 20º C.

According to these rules and variables, we run the model. The next figures simulate the partial coverage of daisies. Conversly, the result of the simulation is showed in the following graphic. In the model, the black and white daisies are represented as black and white features respectively, and the bare ground is red colored.

At the begining of the simulation, the sun's rays are weak and Daisyworld is too cold to support any life.

As the radiant energy of the sun increases, germination of black daisies becomes possible. The black variety is the first in making his apareance because they absorb light, as a result they are warm enough to survive. Eventually, they can spread over most part of the surface of the hypothetical planet. This provokes an increase of the global temperature and allows white daisies to show up.

Both communities can survive together in a dynamic equilibrium for a long time. In this phase, it is possible to achieve certain control of the levels of temperature: black daisies can increase them because they abosrb light and white ones can decrease them because they reflect light.

As the energy of the sun increases, white daisies become to be more adapted than black daisies in this new situation. White daisies can mantain a suitable temperature thanks to their key property: reflecting sun rays. The surface of the world becomes whiter day by day.

In the end, only white daisies can survive for a while in this hell. The sun's rays have grown so powerful that soon even the white daisies can no longer survive.

Daisyworld is a model very simple, but it is enough to show that our planet, the Earth, is in the middle of this simulation. We (human beings) must be there. Lovelock points out that life sustains life. But if something may go wrong, the new environmental conditions that the Earth system creates because of its own regulation, can be extremely damaging (but not for life).

As hard as they try humankind can not eliminate life. On the other hand, it can be very easy to kill themselves.

Thursday, August 13, 2009

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, 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.

Friday, July 10, 2009

Urban Growth Patterns

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


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.

Saturday, May 30, 2009


Welcome to Urban Complexity, a blog where current issues related to the ecology and complexity of urban systems will be discussed.

In this blog you will be able to find essays, reports, biographies, book reviews, news, etc. concerning a wide variety of fields of study like sustainability, bioclimatic architecture, urban ecology, complex networks, Global Warming or landscape management.

We also encourage you to participate and send us any interesting contribution on a topic pertaining to Urban Complexity.