Understanding the systemic nature of cities to improve health and climate change mitigation.

Understanding cities comprehensively as systems is a costly challenge and is typically not feasible for policy makers. Nevertheless, focusing on some key systemic characteristics of cities can give useful insights for policy to advance health and well-being outcomes. Moreover, if we take a coevolutionary systems view of cities, some conventional assumptions about the nature of urban development (e.g. the growth in private vehicle use with income) may not stand up. We illustrate this by examining the coevolution of urban transport and land use systems, and institutional change, giving examples of policy implications. At a high level, our concern derives from the need to better understand the dynamics of urban change, and its implications for health and well-being. At a practical level, we see opportunities to use stylised findings about urban systems to underpin policy experiments. While it is now not uncommon to view cities as systems, policy makers appear to have made little use so far of a systems approach to inform choice of policies with consequences for health and well-being. System insights can be applied to intelligently anticipate change - for example, as cities are subjected to increasing natural system reactions to climate change, they must find ways to mitigate and adapt to it. Secondly, systems insights around policy cobenefits are vital for better informing horizontal policy integration. Lastly, an implication of system complexity is that rather than seeking detailed, 'full' knowledge about urban issues and policies, cities would be well advised to engage in policy experimentation to address increasingly urgent health and climate change issues.