A spatial vulnerability analysis of urban populations to extreme heat events in Australian capital cities

Adaptation Research Grants Program
Margaret Loughnan
Nigel Tapper
Monash University

Executive summary from final report:

Heatwaves in Australia have a greater negative impact on population health than any other natural hazard. As climate change progresses heat exposure stands to cause additional heat-related illness and death, especially for the most vulnerable groups such as older people, young children, people with chronic disease and those living in built-up areas in cities. As a result, the demand for emergency services such as ambulances will increase during hot weather. Community engagement and the ability to enact proactive as well as reactive strategies to cope with increased risk are important components of emergency service heatwave planning.  Communities can adapt to extreme heat events by engaging with emergency managers, local governments and non-government organisations to reduce heat exposures during periods of extreme summer temperatures. This can be done by 1. Changing their behaviors’ and living environments. 2. Building resilience facilitated by understanding the nature and location of high-risk areas and developing targeted heatwave adaptation planning. 

Service providers need specific information to develop heat-related emergency plans for urban centres and to provide guidance for governments and communities on the adaptation of the local environment. This information includes; who the high-risk groups are, where they live, and how risk will change in the future. This study has developed a ‘tool’ to map population vulnerability to extreme heat events in large urban areas. That will assist emergency managers and public health authorities develop adaptation strategies to cope with extreme heat. By identifying areas that show a high-risk of heat-related illnesses and increased service demands during extreme heat events, and by providing a decision making framework to guide future adaptation planning.  

Developing the tool required three steps: 

1. Identification of the daily temperatures at which excess heat-related illnesses and deaths occurred. This was done using daily temperature data from 1999 to 2011. Days that showed an increase in heat-related illness were selected and maps were drawn to show areas within the cities where these events occurred. 

2. Development of an index of population vulnerability to extreme heat using readily accessible data. The local environment, the health status of a population and the demographic structure of a population all contribute to vulnerability. All three aspects were included in the index of vulnerability. When complete the index was used to create a vulnerability map for each capital city providing a visual representation of risk during extreme heat events. The maps can be used to inform discussion between government departments, local governments non-government organizations, community liaison groups and provide advice for adaptation and heatwave response strategies. 

3. To develop effective medium-term to longer-term adaptation plans, we need to know how heat-related risk is going to change in the future.  The temperatures identified in step 1 were modelled for two future time slices (2020-2040 and 2060-2080). This provided an indication of how many extremely hot days we can expect each year in the future. In addition, population projections for each area were used to identify areas where urban density was predicted to increase and areas where the proportion of older residents was predicted to increase. Areas of high urban density require careful planning to offset the urban heat island effect which intensifies heat exposures during hot weather in built-up areas. To help people adapt to hot weather and minimize the risk of heat exposures, information about adaptive behaviors should be made available to high risk groups such as the elderly. This group may also need some modification to the local environment such as shading from vegetation or access to cool places. 

Each step of the study provided information to support specific climate change adaptation measures, and collectively to advise heatwave policy and planning for emergency management.

Key findings for heat-health thresholds

  • Threshold temperatures have been specifically developed for emergency mangers to identify increased service demands for each capital city.
  • Bureau of meteorology weather forecasts for daily maximum and minimum temperature can be used to calculate heat alerts for each city based on  these thresholds. These can be issued to relevant emergency services two or three days prior to the event and updated on a daily basis. Heat alerts can be used by emergency managers and public health practioners to anticipate and prepare for corresponding increases in service demands and save lives.  

Key findings for spatial indices of population vulnerability

  • Variables featuring strongly in the vulnerability indices across all cities are; the presence of an urban heat island, areas with high numbers of older residents, and people who required assistance with daily activities (disabilities). Older people and people with disabilities often live in the higher density (hotter) areas of the city. We need to understand people and place in exposure assessments and developing specific responses to area specific problems.
  • Ethnicity was also an important factor with higher risk noted in non-English speaking homes i.e. people living in culturally and linguistically diverse communities. Stressing the need to provide culturally appropriate information systems. A vital step to help migrant communities manage the heat during Australian summers. 
  • Areas of high vulnerability tended to cluster beyond the inner city areas, with several cities showing an increase in risk along the urban fringe. 

Key findings from future projections

  • Heat extremes are projected to increase substantially in all cities over the coming decades, emphasizing the need to act now to reduce adverse health impacts. 
  • There are areas within all cities that currently show high levels of risk and this is predicted to continue into the future. These are key areas for adaptation and heat-health planning strategies. In the absence of adaptation, heat-related mortality and morbidity will increase. 

Vulnerability indices are useful tools to inform adaptation and increase community and organizational resilience to natural hazards such as heatwaves. We recommend that emergency managers, local governments, and public health authorities use these maps to initiate discourse and engage collaborative adaptation policies. This research has provided a ‘tool’ to guide short-term, medium-term and longer-term heatwave adaptation policy. However it is the judicious application of this new knowledge that will determine whether heat-related mortality and morbidity can be reduced.

View final report and explore spatial distribution maps for each capital city in Australia using a Google Map web interface at Mapping Heatwave Vulnerability.