Urban heat islands: Darwin as a case study in climate change adaptation

Urban heat islands: Darwin as a case study in climate change adaptation

Public Health Association Australia

This Saturday, 5 June, is World Environment Day.

Reimagine. Recreate. Restore. Together, these form the theme of this year’s World Environment Day, a day when the UN seeks to focus the attention of governments, investors, businesses and communities on the increasingly urgent need to restore the Earth’s ecosystems.

As we enter the first chilly days of winter, it’s easy to overlook the growing impact of global warming on our lives. Climate change in Australia has been a critical issue since the beginning of the 21st century. Australia is becoming hotter, and more prone to extreme heat, bushfires, droughts, floods and longer fire seasons, all because of climate change.

Since the beginning of the 20th century, Australia has experienced a steady increase in average annual temperatures, with warming occurring at twice the rate over the past 50 years than in the previous 50 years.

Increasing summer mortality

The results of a recent study published in the Australian and New Zealand Journal of Public Health examined the increased ratio of summer to winter deaths in Australia due to climate change. Capturing a half-century of high-quality climate and health data for a period in which annual average temperatures increased by 1.14 degrees Celsius, this is one of the first studies to associate climate change with human health outcomes.

Whereas in Australia, and many other countries, winter mortality rates are traditionally higher than those in summer, surges in mortality are now a common consequence of heatwaves, particularly in populations with socioeconomic vulnerabilities.

The research concluded that ‘mortality in the warmest and coldest times of the year is converging as annual average temperatures rise’ and ‘if climate change continues, deaths in the hottest months will come to dominate the burden of mortality in Australia.’

While the Australian Government has come under fire for failing to do more to tackle climate change, actions being taken at a state, territory and local government level are delivering promising results.

The ACT Government is now recognised as a global leader in this space. Our national capital is the first city in Australia, and one of the first in the world, to have achieved its target of 100 per cent renewable electricity supply without any use of offsets. It’s also tracking for 100 per cent net zero emissions by 2045.

The Darwin case study

To the north, our hottest capital city, Darwin, is also leading by example. The city sweltered through a record heat wave in 2019, prompting Darwin’s Mayor to declare a climate emergency.

‘I am alarmed at the current escalation in climatic issues affecting our city,’ Mayor Kon Vatskalis said at the time. ‘We need to act now and respond collectively to drastically reduce greenhouse gas emissions through our actions and policies.’

For southern state visitors, Darwin in winter is a fabulous destination to thaw out. For locals, however, the increasing year-round heat is now a major health issue.

A key factor of life in northern Australia, heat impacts on wellbeing and the ability to work safely and effectively, exposure to extreme heat exacerbates pre-existing mental health conditions, negatively affects moods, and detracts from overall quality of life.

Research from Charles Darwin University (CDU) has found that along with the tyranny of distance and high living costs, heat is now one of the key drivers moving people from the tropics to Australia’s cooler southern states.

CDU’s Associate Professor, Kerstin Zander, was the first to examine the economic cost of heat stress in Australia. She found that rising temperatures are now costing the economy billions of dollars each year.

For people aged 50 and over, heat was more important than employment as a reason to leave Darwin and the Northern Territory.

It’s getting hotter!

Between 1910 and 2013, average temperatures in northern Australia increased by 0.9 degrees Celsius. By 2030 they are predicted to rise a further 0.5 to 1.3 degrees Celsius.

The number of days per year with a temperature over 30 degrees in Darwin has also risen steadily. Darwin can expect a significant increase in the number of days per year above 35 degrees, with projected increases from 12 to 43 days by 2030, and to between 111 and 317 days by 2090. It’s a frightening prospect for kids currently in Darwin primary schools, looking ahead to what life may be like in their senior years.

Darwin’s city centre has been described as a ‘heat island’, often experiencing temperatures up to 2-3 degrees hotter than surrounding suburbs. Carparks, roofs and streets have surface temperatures up to the mid 60 degrees Celsius. Now that’s hot!

The horror predictions became a reality just two years ago when, in 2019, Darwin saw a record 45 days above 35 degrees, including a record 11 days in a row.

Professor Mat Santamouris, from the University of New South Wales, says without action Darwin faces both an economic and public health crisis.

‘We expect by 2050 the peak temperature in the city may increase up to 3-4 degrees and this would double, or let’s say triple the energy consumption in the city, and would increase heat-related mortality,’ he said.

Darwin Living Lab project

A big collaborative effort known as the Darwin Living Lab is now underway. It works to reduce the frequency, duration and/or severity of extreme heat impacts, as well as supporting people in Darwin to feel cooler. Its success can generate health, economic, environmental, cultural and social benefits.

The CSIRO, through its Future Cities initiative, is developing a portfolio of Urban Living Labs. While trying to escape the heat on a recent visit to Darwin, I stumbled on an excellent Darwin Living Lab exhibition in the City Mall. It’s a 10-year collaboration between the CSIRO, the Australian and NT Governments, and the City of Darwin, which aims to improve the liveability, sustainability and resilience of the city.

It creates a place where researchers, industry, government, regulators, public health officials, developers, businesses and the community can work together to address some of the environmental, social, economic and technological challenges facing Darwin – none more important than the impact of heat stress.

The first phase of the Darwin Living Lab project has seen the development of one of the world’s biggest Heat Mitigation Strategies to improve liveability and help cool the city. Importantly, the project has developed a monitoring and evaluation approach to track the changes and any progress made.

A heat mitigation study undertaken by UNSW presents several different scenarios to bring Darwin’s outside temperatures down. These include:

  • Use of cool pavements to reflect the sun’s rays which has been tested to deliver a temperature drop in the CBD of up to 2.2 degrees.
  • Reducing solar radiation on streets and carparks by 30 % via shading would result in a maximum temperature drop in the CBD of about 1.2 degrees.
  • Increasing the greenery to cover 20% of Darwin’s CBD will result in a maximum temperature drop of 2.6 degrees.
  • Implementing green roofs in all buildings would result in a maximum temperature drop in the CBD by about .5 of a degree in the area immediately surrounding a green roof
  • Adding 10 water fountains in the city mall was modelled as being able to deliver a maximum temperature drop of 3.9 degrees in the immediate area.

Progress so far

Wandering Darwin’s city streets, there’s already significant evidence of progress made in the first two years of the project.

Identified as Darwin’s hottest street, Cavenagh Street was selected as an ideal site for heat mitigation.

When Cyclone Marcus hit Darwin on 17 March 2018, it caused widespread damage, including the destruction of much of the city’s treescape and the loss of an estimated 10,000 trees.

The picture above shows the decimation of the landscaping which left the wide street unprotected from heat. Temperatures in Cavenagh Street were recorded at more than 60 degrees which also acted as a ‘wind duct’ carrying the intense heat through to other parts of the CBD.

Subsequent plantings and the erection of a large shade structure is already having a positive impact on temperatures in this busy CBD street.

Similarly, plantings in nearby Daly Street have had the dual impact of beautifying the area and reducing the impact of heat.

Since declaring a climate emergency in 2019, the City of Darwin Council has created an action plan with four main goals:

  • Promoting resilience and adapting to climate change
  • Achieving net-zero Council controlled emissions by 2030
  • Supporting the Darwin community to achieve net-zero emissions by 2040
  • Identifying new economic opportunities

The progress to date is impressive. Since Cyclone Marcus more than 12,000 trees have been planted across streets, parkland and reserves, and much of this work has been led by schools and community groups. A further 5,500 trees will be planted over the next four months.

Darwin is facing a massive challenge but deserves great credit for its proactive and evidence-based approach. It may well prove to be both a life-saver and a city-saver!

If its heat mitigation strategy proves successful, Darwin could well become a model for many other cities in the world facing their own climate crises.


The article ‘Increased ratio of summer to winter deaths due to climate warming in Australia, 1968-2018’ published in the ANZJPH, was jointly authored by Ivan Hanigan, Keith Dear and Alistair Woodward.

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