E&E professor Luis Bettencourt on developing more livable, sustainable cities
Bending the resource flows of cities toward circularity. (a) For any complex system, including cities, energy must be supplied from external environments, and becomes partly embedded in products, information, and the built environment. Most of this energy is dissipated as heat (red lines). Materials entering the city (green lines) cycle out as wastes that are eventually reused by both human societies and ecosystems. Urban sustainability calls for increasingly complete and local cycling of materials, creating a more circular urban economy. (b) Different materials cycle very differently in terms of their spatial and temporal reach. These Differences can be characterized by a radius of circularity, Rc(Mi ), and a period (smaller green loop), Tc(Mi ), for each material Mi respectively.
As the world continues to rapidly urbanize, in a few decades we will find ourselves inhabiting a “planet of cities” that are larger and more complex than ever before. How to better plan and develop cities so that they truly meet the needs of diverse populations, at the same time minimizing their impact on the environment, is therefore crucial and urgent. In a recent paper, E&E Professor Luis Bettencourt explores how we can work towards these goals with new conceptual and analytical tools, using science-based approaches to make cities more livable and sustainable.
In a paper entitled “Emerging Scientific Frameworks and Tools for Sustainable Cities”, published recently in the International Journal on Smart and Sustainable Cities, Professor Bettencourt examines the “uneasy discipline” of urban planning, which in the past has often offered utopian visions of cities based on simplistic concepts rather than “empirical realities of existing and past cities”. He highlights a new way of thinking about urban improvement that begins with a scientific attitude towards cities and a better understanding of their underlying processes. To this end, he examines two analytical tools: the ego-network of functions for person-centric city design, and the circular diagram of urban material flows for more circular economies and sustainable cities.
The ego-network of functions visualizes the accessibility of all the functions that fulfill a person’s needs. Reflecting the heterogeneity of cities, agents at the center of the network can be changed to “provide a diversity of tests on urban equity and livability.” The cumulative data can inform urban planners where public intervention is necessary to improve the quality/quantity of functions to better serve the varied needs of urban populations.
Ego-Networks of Functions. (a) In urban environments people are interdependent, meaning that they must obtain all their functions from each other, in ways that are comprehensive, accessible over space, and that fit their monetary and time budgets. (b) Individual and household functions are obtained over space, along people’s trajectory (or life-path). This requires a match between a person’s residential location, their mobility, and the full set of functions necessary for a good life. By varying the individual at the center of the network and considering their specific contexts, the person-centric diagram becomes a flexible tool for addressing issues of heterogeneity and environmental equity. Individuals with special needs, such as with (c) a disability, (d) ageing, as well as with children, migrants, or the poor, will require special functions.
A circularity diagram of urban material flows visualizes a city’s intake of energy and materials and output of waste or carbon and environmental impact. It shows the network processes involved in creating circular urban economies and achieving sustainability. The agent at the center of the diagram can be a city, but could also be a household, a firm, or even a neighborhood community. The point is to have an analytical tool for material and energy flows that can be performed around any city, with the ultimate goal of containing such flows more locally to create more sustainable cities that “do not degrade external ecosystems as sources of materials or change the Earth’s atmosphere as a sink for pollutants, such as CO2.”
The thinking behind such tools reflects a new mindset in considering cities and how to make them better. Namely it calls for a scientific approach to all the data that is available from cities around the world, building up knowledge over time that contribute to methods and analytical tools to help create more livable, equitable, and sustainable cities for the future. As the paper concludes, this “analytical approach supports a practice of planning that must become rich in evidence, driven by hypotheses, and subject to empirical testing, bringing the logic of science and the ability to learn cumulatively to urban practice in a way that has so far been uncommon.”
