Could urban disorder give way to sustainability?

24. An EPFL researcher is modeling cities in order to understand their metabolism and determine their ecological impact when they grow and change. Her research is aimed at identifying the urban form that is most efficient and consumes the least amount of natural resources. With cities expected to grow significantly in the future, it is vital to plan their development and anticipate their impact on the environment ahead of time. Nahid Mohajeri, an urban architect and geographer at EPFL, looked into Geneva's history in order to understand how the city developed the way it did and predict how it will change in the future. In order to model a city's evolution over time, Dr. Mohajeri came up with the idea of combining two different scientific approaches: statistical thermodynamics - comparing cities to large ecosystems that change and produce waste and CO2 emissions - and information theory. Preliminary results, published in Ecological Modelling, indicate that cities in general - and Geneva in particular - grow by virtue of two very different processes: they spread out and/or become denser. Dr. Mohajeri also observed that large cities are proportionally more energy efficient and have a lower specific ecological footprint per resident than small towns. For the purpose of quantifying the different cities, the researcher analyzed them in terms of their thermodynamic entropy, which scientists call "randomness." She also used other physics and engineering methods, such as spatial analysis. In this way, Dr. Mohajeri was able to model cities on a computer. The goal is to compare the ecological impact of various urban forms - compact or dispersed - in view of one day developing a framework for building eco-cities. But is there really an ideal urban form?