Healthy, just and eco-sensitive cities: moving forward

Abstract

Obesity has reached epidemic proportions in many countries and persists despite continuing efforts to find solutions. Such ‘stubborn problems’ often signal the influence of ‘feedback systems’. In the case of the obesity epidemic, this possibility can be investigated using available system analysis tools. The investigation must begin with a study of the interplay between the full range of human and environmental factors. This paper outlines the nature of feedback and briefly discusses some of its management implications. A practical way to initiate a ‘systems approach’ to the obesity problem is suggested and four principles to guide the management of complex human– environment systems are presented. Barry NewellA,C, Katrina ProustA, Robert DyballA and Phil McManusB AFenner School of Environment and Society, The Australian National University BSchool of Geosciences, University of Sydney CCorresponding author. Email: barry.newell@anu.edu.au pressure on selected system variables (or the severing of selected causal links) will produce the desired outcomes. These are the elements of a ‘systems approach’. Feedback and its effects The ‘behaviour’ of a human–urban system, the way that its variables change over time, emerges from interactions between these variables.4–6 When a change in the value of a system variable is amplified by the system, the effect is called ‘positive feedback’. The term ‘positive’ indicates only that changes are reinforced – it does not mean that the effects are necessarily good. Positive feedback effects are sometimes called runaway effects, bandwagon effects or vicious circles. They can lead to exponential growth or collapse. When a change is opposed by the system the effect is called ‘negative feedback’. Negative feedback effects work to hold system variables at established levels, thus stabilising the system. Note that the term ‘negative’ indicates only that changes are resisted – it does not mean that the effects are necessarily bad. The various homeostasis mechanisms that maintain stable conditions inside the human body are all examples of ‘good’ negative feedback. These effects can be illustrated using ‘causal loop diagrams’ (the commentary associated with each of the following three figures explains how to approach a causal diagram). Figure 1 provides an example of a systems effect that is commonly called ‘policy resistance’ – a major cause of stubborn problems. The diagram can be read as follows: a desire for a high level of outdoor activity leads to an increase in the amount of open space preserved in the neighbourhood. Open space increases the popularity of the area. Increased popularity leads to a demand for additional housing. Finally, the demand for new housing leads to development pressures that can result in a reduction in the availability of open space. In this case, a possible leverage point involves breaking one of the links in the feedback loop – for example, the policy resistance can be removed if the pressure to develop open space is resisted. The example shown in Figure 2 illustrates the amplifying effect of positive feedback. There is a negative feedback loop that operates to maintain the extent of the obesity problem. In this loop an increase in the number of obese individuals causes an increase in the popularity of weightloss programs. Then, the increase in the popularity of weight-loss programs reduces the extent of the obesity problem. But the tendency to see weight-loss programs as ‘the solution’ reduces efforts to identify and address the