"Ne quid Nimis" [nothing in excess ]Sustainability can be, aside a trendy tag, a desirable life perspective with high impact within our cities system as long as we make a personal task. Luis Suarez pointed rightly in his recent post when talking abut individual consciousness.
Individual behaviour (usually manipulated by industrial consume model and mass media) has important consequences in the process of co-evolution between techno-sphere and the biosphere, as long as more population demands more resources. The crucial problem is not population growth, but the fact that population keep consuming resources in an unsustainable way. There are sectors of world population that constantly generate pressure on demanding more resources only to maintain their lifestyle.
The concept of ecological footprint is very instructive as indicator of this phenomenon. The ecological footprint is a measure of how much biologically productive land and water an individual, population or activity requires to produce all the resources it consumes and to absorb the waste it generates using prevailing technology and resource management practices.
At this point, most people have the belief that science and technology will find the solution and take us through the path of "sustainable development." Technique and technology are important, as long as they are reinforced by common sense. If we maintain the same consumption patterns while increasing technological efficiency what actually occurs is a rebound effect known as the Jevons paradox which states that resource consumption increases when increases its efficiency. It means that when efficiency improves, production increases and therefore, consumption. Here, we can quote José Manuel Naredo, when he pointed "This technological optimism, in fact extractive, is therefore incompatible with life." If we consider that "the second law of thermodynamics can not be ignored."
The growth limits do not pass through the optimum use of resources, neither by improving technology. The boundary is defined by the law of entropy, that describes the degradation of matter and energy in the universe. In fact, economy is an open system that can not function without the input of energy and materials. According to Joan Martinez Alier, the conflict between economy and environment can not be solved simply with phrases such as "sustainable development", "eco-efficiency" or "ecological modernisation". The clash between economy and environment seems to be inevitable, and Martínez Alier adds that therefore, we still needs to invent something new, a vision that does not depend on politics, but rather on social movements that reinforce it.
Proposal for a social approach to sustainabilityNicholas Georgescu-Roegen pointed that in the future the fundamental scarcity would not be due to energy (given the existence of solar radiation), but depending on materials, taking in consideration that Earth is an energy-open but materials-closed system. The question is not whether the 21th Century cities may be sustainable or not. The crucial fact is that our entire system of production and consumption needs a deep revision. This can be achieved as long as we abandon "growth rates" and "development" (even if sustainable) as economic and political objectives and focus on other convivential and relational goods, which consequently will be reflected in all our achievements, including architecture and our cities.
A clear awareness of the material and energy limits of our activities is essential to reach a balanced relationship within the system. It is possible that this will lead to courageous proposals as to stop or reverse the growth of our cities. Changing our mechanical growing paradigm and our production system would result in the conversion of economic activity as we know, which is deeply rooted in our collective unconscious as synonymous of progress.
In this process of assimilation and conversion, will be crucial the community support to absorb the countless number of people who need to change their labour activities. At this stage starts to make sense to encourage activities based on convivential exchange of goods (in the sense pointed by Ivan Illich) , labour support and network assets in the creation of open source systems that allow appropriation and adaptation to the specific situation where apply (e.g. time banks, local currencies, barter of services, open source software).
We have proposed an open formula, which allows new variables in case anyone wants to contribute. With didactic vocation, it shows the increasing importance that relational goods must have against other "values" that until recently we thought unassailable.
 Ramos, Vitorino "Charles Darwin’s Scottis kilt " http://chemoton.wordpress.com/2010/05/05/charles-darwins-scottish-kilt/. Web May 07 2010.
 Global Foodprint Network. http://www.footprintnetwork.org/en/index.php/GFN/. Web May 06 2010.
 Interview points by Monica Di Donato CIP-Ecosocial http://www.rebelion.org/noticia_pdf.php?id=81315. Web May 06 2010.
 Illich, Ivan. "La Convivencialidad" (Tools for Coviviality) . Barral Editores. Barcelona 1978.
This Guest post by dpr-barcelona | Ethel Baraona + César Reyes forms part of the discussion in the urbanTick series on Ecological Urbanism
dpr-barcelona is an innovative publishing company based in Barcelona, specialised in high quality architecture and design books. With an international scope and founded by two architects, their titles vary from monographs and documentation of buildings to historical studies, collections of essays and dissertations. Showing a clear innovative way to bring the contents to the public, their projects transcend the boundaries between time and space from conventional publications, approaching to those which are probably the titles of architecture in the future.