Evaluating natural experiments to measure the co-benefits of urban policy interventions to reduce carbon emissions in New Zealand.

Finding effective policy interventions for addressing the Sustainable Development Goals, such as reducing carbon emissions (SDG 13), which can also enhance good health and wellbeing (SDG 3), is urgent. Many promising interactions occur between sustainable cities and communities (SDG 11), clean water and sanitation (SDG 6) and affordable and clean energy (SDG 7), which sit at the centre of integrated urban planning and regeneration. In this paper, we consider the framing and findings of four policies we have evaluated as natural experiments, all of which have important co-benefits, which were not always the focus of the initial policies. These policies are: the installation of cycleways and walkways in existing suburbs; a central government measure to recentralise employment after the 2011 Christchurch earthquakes; the streamlining of housing developments by reducing land-use regulation; and ongoing changes of policy about public housing investment. We show that having a clear understanding of the benefits of increased physical activity for health, for example, could accelerate the reduction of carbon emissions. Also, decisions about infrastructure, housing and job locations can generate health and environmental gains if supported by broader public transport investments. Cycling and walking are also more likely to substitute for short habitual car trips. Similarly, measuring the co-benefits of differential residential models, relating to land-use and renewable energy, provides a framework that can facilitate learning from policy interventions, enabling wider and potentially more rapid generalisation of policies, including those for climate change mitigation.