The colossal problems of global urbanization and the depletion of natural resources force us to re-think the city in the 21st century. We need to get over the failed models of the recent past, but also look to traditional urbanism for successful patterns that were thrown out with the advent of industrialization. Two distinct ideas prove promising here: to conceive the city as a network, and to implement peer-to-peer methodologies in designing and repairing the urban fabric.

The city is a connective network among human beings and their activities. This is what led to urbanization in the first place: individuals clustered so that communication distances diminish to a minimum, while the number of connective nodes increases. Living cities are overlapping networks of information exchange. Each network functions on its own hierarchical level (this does not necessarily mean a physical separation of different levels), and all networks are interconnected. Information exchange includes the physical movement of goods, transport of people for the purposes of personal contact, information exchanged between persons and their urban environment, pedestrian mixing in a safe urban space, mechanized movement over larger distances, and information exchange over virtual channels of communication. All of these cooperate to define a living city as a complex system with emergent properties.

The networked city exists to facilitate distinct types of information exchange, and is governed by flows. Physical urban objects and virtual information can usefully interact using distributed sensors to monitor energy use and flows. Cities in the past developed spontaneously much as today’s informal settlements (favelas), then underwent repeated upgrading to become the historic city centers we find today. Most important, the physical geometry of the city was a response to the informational flows. The city’s structure is dictated by information exchange through networks: the shape and positioning of paved roads, buildings, bridges, and built infrastructure is determined by the networks. In some instances, built urban fabric came first, as in planned colonial cities of the past, but it was always strictly subservient to facilitating network flow.

An informational system analogous to a “nervous system” could be implemented in today’s cities through a network of sensors, which will then help the city to re-adjust its morphology in becoming more sustainable. A responsive sensing network by itself cannot save sculptural buildings set in formal planning that waste energy and resources, taking precedence over physical networks. Optimizing interacting physical and virtual urban networks through feedback results in a healthy and more sustainable city.

Post-war sprawl may be network-driven, but only for the private automobile network. It ignores and erases other networks necessary for city function, creating a dysfunctional city. The solution is massive re-centralization and densification of sprawl. Starting in the 1920s, planners somehow forgot the causality of urbanism — that multiple networks define the built urban structure, and not the other way around — and began building urban geometries that are irrelevant to, and prevent the spontaneous formation of network connectivity. Therefore, in high-density settlements from the post-war period, networks are weak or non-existent. That giant error has to be propped up by an enormously wasteful energy-based fix. We can no longer afford to artificially support geometrically inefficient urban morphology, and should re-structure the city so its built form fits with its essential networks. Optimization relies on real-time sensing that shows how to minimize path-lengths and energy use.

The second key idea for the urbanism of the future, P2P methodology, can be adopted to re-generate the city. Peer-to-peer is a movement that began with software sharing, based on the principle that everyone can contribute across an information-exchange network. It is now feasible to write open-source rules for urban planning on a P2P platform. The crucial distinction with government-imposed top-down planning is that the residents themselves can judge what is to be built, and how it is to be built. Thus, with the active and direct participation of users, it should no longer be so easy to bulldoze thriving urban fabric, forcibly move residents to outside the city limits, permit speculative construction to ruin agricultural land, erase centrally located network nodes, impose some giant project that profits only a multinational company, destroy the vibrant life of an existing community, etc.

Dysfunctional urban fabric (a large percentage of post-war construction) can be re-built, sometimes with only minor interventions, according to a bottom-up process. Here, the eventual users come together informed by the distributed knowledge of human-scale urbanism, and either build the city themselves, or insist that their political representatives work for them and not for some central power structure. The worst anti-human insertions into the human fabric are the fruit of centralized planning coupled with vested power interests. The individual’s freedom to enjoy the multiple networks of a living city was invariably repressed in favor of ideology and profits at the expense of humanity. Sadly, misinformed professional planners promoted those anti-urban projects, in a giant deception offering utopian promises of social liberation.

Where a P2P ethic and effective platform for cooperation exist, even if restricted in geographical scope, it is finally possible to take decisions from the ground up. This situation certainly holds true for many informal settlements, which could be upgraded at comparatively small cost without destroying their vitality. Instead of forcing those residents to fight a constant ideological battle with the government, resource optimization is possible through cooperation. This is really the only way that any nation can approach sustainability. It is simply too expensive in energy consumption to continue with large-scale industrial type housing schemes.

We stand ready to re-shape our cities for the 21st century so they maximize information exchange through networks. This morphological evolution using feedback and selection will optimize energy use and improve sustainability. Perhaps for the first time in history, using P2P, we can disseminate freely the discovered bottom-up rules for human-scale urbanism. Once a number of citizens learn these rules, and realize that the centralized power structure has no secret method for building a city, we can begin the process of physically healing existing anti-urban parts of the city, and generating living urban fabric in now-dead regions. We thus overcome the problem of “design” that kills networks. People only need to realize that this goal is possible.

Eight points for rebuilding the city.

1.  Governments can cooperate with their citizens in harnessing bottom-up and self-build initiatives.

2. Human-scale urbanism necessitates feedback through sensors, and the ability to adjust urban form to optimize connections and energy use. This is the direction towards sustainability.

3. Energy and resource optimization depend upon a system of overlapping networks that enhance but do not cut each other. Do not privilege any single network.

4. Build new urban fabric that incorporates network connectivity and the human-scale features of traditional settlements. Connectivity overrides formal concerns of the plan.

5. Virtual networks, upon which modern society depends, must be supported by a similar highly connective structure of physical networks.

6. Network connectivity determines the geometry of the urban fabric, therefore be suspicious of any proposal that looks too “clean” and “stylish”.

7. Dead urban fabric can be re-vitalized with mostly minor interventions, but we must be able to move roads and cut into blocks. Optimized restructuring depends upon users’ participation.

8. Some urban mistakes are irredeemable, thus only after their demolition can living urban fabric be created there. Don’t believe sociologists who claim physical form is unimportant.