City Systems Workshops

Chair: Sander van der Leeuw, Arizona State University





Session 1: Thursday 8th November 15.15 – 16.45:

General: this set of three sessions is intended to generate questions and new ideas for future research. I therefore suggest that after a very quick round of introductions and two very brief introductory statements for each session(that I will invite personally), we devote all our time to discussion.

In order to facilitate that, I would like to receive from anyone who is so inclined, tentative answers to the ‘What’ and ‘How’ questions formulated for each session. That will greatly help me steer the sessions to a productive result.


Main questions


  • What drives the seemingly inexorable growth of urban systems?
  • What might level off this growth?
  • What would a generalizable theory of urban systems look like?


  • How would we collect, and deal with, the data?
  • How could we model it?
  • How could we derive scenarios from the models?
  • How might such a model serve to improve decision-making?



Contributors / participants:


Luis Bettencourt. Ricardo Herranz, Denise Pumain, Jose Javier Ramasco, Moritz Remig, Wanglin Yan, Maxi San Miguel, Alan Wilson, Michel Morvan, David Lane




Session 2: Friday, 9th November 2012, 14.30 – 16.30:

Main questions:



  • What would a sustainable city look like?
  • What would make urban systems more sustainable?
  • What are the trade-offs that would need to be dealt with?
  • What kinds of institutional change would this require?
  • What kinds of policies would need to be put in place?


  • How could we mobilize society to that effect?
  • How could ICT play a role in this process?
  • How could ICT create a synthesis between ‘top-down’ and ‘bottom-up’?


Contributors / participants:


Vittorio Loretto, David Lane, Michel Morvan, Denise Pumain, Maxi San Miguel, Alan Wilson, Luis Bettencourt. Ricardo Herranz, Jose Javier Ramasco, Moritz Remig, Wanglin Yan


Session 3: Saturday November 10th, 9.30 – 10.30


Chairs: Carlo Jaeger and Sander van der Leeuw


This workshop will be oriented to identify and discuss common questions between the different workshops following the insights gained from the previous discussions. So the topics will be adapted to the results of the prior days.




Anyone of the above (and the Global Systems Science sessions) that is still present and interested




3 thoughts on “City Systems Workshops”

  1. Report on session one of CITY SYSTEMS (Prof. Sander van der Leeuw), Thursday (8th Nov.)

    All participants agreed so far on the principle to “learn from good examples”. Essential questions (‘What’) call for better methods & descriptions of city systems, based on a growing amount of avaiable data. As these systems exhibit (A. Wilson)
    – a strong path dependance of development and
    – a challenging high dimensionality.
    They call for intelligent databases within a “global” context and modelling solutions (not start-from-scratch!) that are understandable/transparent for users. It seems important here to stress on both the conceptional, spatio-temporal multiscale structure of city systems (of systems)(D. Pumain) as well as the organisation of cities and their levels of sub-systems, identified by their functionality (C. Barrett).
    In the context of a massively growing amount of avaiable data, “you cannot just look at the data and hope to get an epiphany” (L. Bettencourt). Arising questions are..

    Which kind of structures emerge?
    Which of these really matter?

    Cities, basically, are social networks, embedded in space-time through infrastructure. So the essential key to the existence and development of cities is connectivity.

    … arising questions of the session:

    HOW are contributing variables identified as city-state-variables (statistical mechanics)?
    HOW are the concepts best implemented in the presence of BIG city data?

    Concerning the wicked nature of the existing challenges [referring to “Dilemmas in a General Theory of Planning” (1973) by Rittel&Webber] in describing complex city systems, a great deal of effort has to be put into asking the right and precise questions.

  2. To the challenging questions raised by Sander van der Leeuw, I would give the following answers for entering the discussion

    • What…
    o What drives the seemingly inexorable growth of urban systems?

    There are several levels and types of driving forces, and their effect may change according to the time scale for observation.

    Regarding population growth, the main driving force is in the last stage of demographic transition and rural-urban migrations in most of developing countries (among which the largest and less urbanised, India and China, as well as other parts of Asia and Africa), that will provide some 4 billions new urban citizens in the world before the end of 21th century. This means roughly more than doubling the existing global urban population.

    The reasons explaining the prolonged attractivity of urban areas on populations are modulated according to the geographical level of observation: for individuals, urban areas offer in average better prospects in terms of income increase, health care and life expectation; in the case of firms, urbanization economies supplied by urban areas (infrastructure of all kind, including proximity to market and human capital) are essential in attracting their location decisions; at territorial level (infra-national regions, nations, supra-national regions, and globally) there is also an inter-urban dynamics of emulation (including competition and cooperation processes) that sustain a slight but rather continuous historical trend to increase urban concentration (i.e. although urban growth is widely distributed in integrated systems of cities, large urban areas are growing slightly faster and smaller towns less, many of them will probably shrink in the future).

    At that scale (systems of cities within territories), the dynamics remains on the whole self-organised.

    Even if less documented and difficult to analyse (because of a lack of reliable data and conceptual bases for weighting measurements of different nature) the main driving force is about maintaining the quality and increasing the quantity of urban assets (economical, environmental, societal, patrimonial, symbolic…) that are the aims of and benefit to a plurality of stakeholders, not only local residents but all those connected in a multiplicity of networks at many institutional and geographical levels. The urban geodiversity (i.e. the co-existence and interdependency of cities having different size and functions) is both a result and a condition of this accumulation process.

    o What might level off this growth?
    Sorry for searching again lessons in the past, but the only periods in history for which the dynamics of urban concentration (at the level of systems of cities) was interrupted are periods of wars (civil or international) and other severe catastrophes (epidemics, famine).

    From our observations and simulations, it is likely that even if further concentration is limited in terms of population growth after the end of demographic transition in a few decades there is no reason for expecting putting and end to the process of urban assets accumulation and concentration.
    o What would a generalizable theory of urban systems look like?

    It would be necessarily a theory grounded in social sciences and human ecology, integrating concepts of a series of disciplines as well as principles from complex systems sciences. The theory has to take into account simultaneously the general dynamics of urban systems and the historicity that generated their cultural diversity demanding specific adaptations of any general policy requirements.

    • How…
    o How would we collect, and deal with, the data?

    As local national urban definitions are highly variable, painful and lengthy work of data harmonisation are necessary before any scientific analysis. An agreement about the relevant concepts is possible (as demonstrated for instance within the European ESPON programme on urban data).
    o How could we model it?

    Different methods are possible according to the question. Statistical analysis already reveals a lot. Multi-agents systems are good candidates for exploring more sophisticated questions and formalising interactions between different global systems.

    Models at global scale have to be rather large to take into account enough of the relevant systems and urban diversity. That means using adapted massive computing for dealing with a large number of spatially explicit interactions.

    o How could we derive scenarios from the models?

    Many unknown parameters connecting different global systems have to be estimated. Fortunately grid computing and adapted validation methods may give more confidence in the estimated results from the model. Plausible scenarios could thus be derived in a safer way.

    o How might such a model serve to improve decision-making?
    By delineating the range of possible futures under a limited number of hypothetic relationships, the model would give a chance to derive a plurality of local strategies leading to a better adaptation of each subsystem to the expected trends in the global system.
    But it must be kept in mind that there is no institutional governance at the scale of the global urban system, and even at local level the local administration does not usually cover the geographically consistent area that would be necessary for making more rational decisions. However, in spite of the lack of institutions, there is kind of “de facto” urban governance that occurs in a multi-scale way under the many initiatives for applying, imitating or anticipating at local or national levels the regulations that are elaborate for mitigating the effects of climate change and shrinking of resources.
    Denise Pumain

  3. Session Friday November 9, 2012: “City Systems”.

    As a participant I have the following observations and comments to make. I merge the observations made in the session with a few new elements in order to share at best the experiences and information for further action:
    1. “city systems” as the abstract notion to the “reality” of urban development: in terms of environmental impacts “food. houding and mobility” are core and relate to a great extent to cities: e.g. UNEP resources Panel on “Decoupling”; in relation to the EU and more broadly OECD countries the need to transform the economy by reducing material use (identified as a “factor 10”- issue “over the next three to four decades” in an analysis tabled in the EU Environment council of ministers in 2010 “Sustainable materials management (Catholic university of Leuven, Wuppertal institute, Sostenuto). The concept of “urban metabolism” may well be relevant here: I heard about it last week, November 5, at a seminar : see about “the sustainable city as an ecosystem”.

    Combined with the social issues of access to health care and education in cities (in Europe, and of course also worldwide) – described as wicked issues in the session -, ‘city systems” cover a core area for early and effective action: “Renovation” as one focus will have to combine the “deep” and the “social”. “Global Energy Assessment” 2012 by IIASA c.s. has a very relevant observation about the quality and pertinence of the required policies to obtain the expected deep cuts in GHG-emissions. Potential of net employment creation via broad urban renovation.

    2. The link “GSS”- society could be developed very fruitfully when looking at the numerous initiatives that are ongoing in the European Union, related to initiatives I am involved in in Brussels, not awaiting the outcomes of the GSS-project but by “interacting now”:
    – the role of local authorities and the potential to engage with citizens, social housing initiatives and a very recent example (e.g. ICLEI), in support of a broader process in society of democracy and decision making about sustainability issues and solutions
    – emergence “around the EU” of a broad set of platforms of professional initiatives, think tanks and “action-oriented” think tanks. http://www.BPIE.EU – “building Performance in Europe” – as an example of the latter (energy efficiency, renewable energies, datahub), an initiative linked to same in a number of other regions globally
    – urban development and the option to include “urban metabolism” and examples (Geneva;
    – the link with “Finance” e.g. the need to overcome the obstacles to a mature market for energy efficiency (EE): see seminar BPIE November 7 about “Securing Finance for energy efficiency”. The observation that currently actions for “EE” undertaken at the level of member states are fragmented geographically within a given member state and a”single market” for the best options is not yet there.

    Ongoing EU-decision making in areas such as Water (Framework Directive and water pricing) or Waste is a factor in and by itself: the new phase of Prevention as from December 2013 of the current Framework Directive is a relevant “test case”. A possible “benchmark” is to analyse the nature of the decision making process in terms of “integration” in support of the interrelated issues of urban development in a “city system”.

    I will be glad to help in further “connecting” science and society in this dynamic, demanding and crucial area of city systems.

    Gertjan STORM
    honorary advisor “science, policy and sustainability”,
    ICIS, university of Maastricht:;
    and to “European Partners for the Environment” a multistakeholders’ platform, Brussels:

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