Synergistic nature of sustainable development solutions centred on heat stress in the urban system

The increased frequency of extreme weather events – a consequence of both man-made climate and land-use changes – pushes city governments to implement measures to ameliorate the impacts on city inhabitants. While governments are working to develop solutions to address heat, drought, and flooding, these challenges are often tackled separately through differing disciplinary lenses. However, individual measures may either compete with or complement one another; and it is critical to gain a better understanding of this interactions.

In this research, we use systems mapping approach to combine the varying disciplinary perspectives of urban climate measures. We aim to identify critical areas where improved information flows could enhance decision-making and policy integration. Here, we use a systems map to point out how a few active measures can act as leverage to ameliorate heat stress while having synergetic effects on other sustainable development goals and increasing the system's resilience against extreme events. The work is partly based on results of the project Imp_DroP (Impact of longer Drought Periods on Climate in Greater Vienna: appropriate Mitigation measures) and discussions with stakeholders. The system borders are defined as the actual city borders during summer heat and drought condition. The system includes all important geophysical parameters as well as planning solutions in the building sector, traffic planning and urban open space design that are known and discussed to mitigate heat stress.

Important levers driving change are cooler building envelopes, (tree) shade in pedestrian areas, and increasing water-holding capacity, which can contribute to both a reduction in local temperatures and a decrease in the city's contribution to greenhouse gas emissions. Both indoor and outdoor thermal comfort are considered, as they are highly connected. Irrigation volumes and anthropogenic heat emissions are tackled as well as competition for public space and roof area.

From a system level perspective, a set of balancing loops could be identified in and across subsystems that can help in understanding and facilitating sustainable urban development. While ‘simple’ technical solutions can be of isolated nature (fixing only one problem and likely causing unintended side effects), other solutions such as increasing the availability of urban open space for pedestrians and vegetation are more difficult to implement, but have a reinforcing character, the potential to solve multiple problems across the system including enabling higher quality urban environments.