The urban heat island effect impacts people (especially the most vulnerable), buildings, transport operation and infrastructure, energy demand, the economy and the health of trees and animals.
In a previous article, we showed how cities are contributing to climate change via the urban heat island effect (UHIE).
Curbing heat stress and adapting to a hotter climate requires systems thinking. Here we propose a framework of solutions for addressing UHIE, including:
1. Accepting scientific evidence
This is self-explanatory, science is clear about an increase in hotness and dryness.
2. Resilience thinking
How can we thrive in the face of a changing climate? How can we make sure extreme events like heat waves don’t cause casualties and mass disruption? How do we maintain the functioning of a city while creating change to be a different kind of city? Resilience thinking is part of the answer.
Resilience thinking investigates how human systems interact with ecosystems and how they can best be managed. Stockholm Resilience Centre (2014) has developed seven principles for applying resilience thinking: 1) maintain diversity and redundancy, 2) manage connectivity, 3) manage slow variables and feedbacks, 4) foster complex adaptive systems thinking, 5) encourage learning, 6) broaden participation, and 7) promote polycentric governance systems.
For example, UHIE impacts have a spatial/ geographical dimension and temporal dimension (which is less understood). People living in inner city will experience heat stress at night time when dense built form radiates heat back, while those living in outer suburbs will experience it during daytime.
3. Nature-based solutions
One important option to curb urban heat stress is to think about nature-based solutions (NBS) and increase green (vegetation) and blue (water) infrastructure within cities, which also improves biodiversity. However, green and blue infrastructure rarely get emphasised unless tied in with other benefits. NBS provide co-benefits for addressing societal challenges such as climate change adaptation, while simultaneously promoting ecological health. NBS is the practice of working closely with the natural environment that is inherent to many Indigenous practices.
In this article we expand on these types of solutions that have been applied in Singapore and South Australia, that other cities such as Melbourne can learn from.
4. Challenges for addressing UHIE in Melbourne, Australia
Many local councils in Australia now have “urban greening” strategies. They indicate that while solutions to address UHIE are available and increasingly well understood, there are major barriers to implementing them, as highlighted in a recent report by the Environment and Communications References Committee (2018) to the Senate.
One of the biggest barriers is the local government’s lack of resources for implementing urban forest strategies. There is also a lack of appropriate planning mechanisms such as revegetation requirements on new developments or private land, provisions for protecting existing vegetation, and management of introduced green/blue infrastructure.
Integrating biodiversity in cooling strategies is another significant challenge. If the co-benefits of such infrastructure – such as reduction in heating/cooling bills or water basin management – are not well understood, then there is no incentive for vegetation on private developments.
Another major hurdle in addressing UHIE is changes in grey infrastructure (for example, buildings, roads). The construction material used – type, colour, reflectivity etcetera – has an impact on heat accumulation in cities. Materials chosen primarily for strength, aesthetic or cost-efficiency may exacerbate heat, and even fail to provide indoor thermal comfort. One example is concrete and glass facades on buildings – both of which not only heat the outside environment, but are highly inefficient for maintaining indoor thermal comfort.
A balance is necessary between economy, constructability, building performance and the future adaptability of our cities. However, there is no mention of UHIE as a factor in building design on the Australian Building Codes Board.
The case of Melbourne
With an urban area of over 9990km2, Melbourne is 80 per cent urbanised and is home to 4.9 million people. Melbourne is projected to surpass Sydney as Australia’s largest city by 2066. Greater Melbourne is projected to grow to 11.2 million people by 2056, with 9 million living in Melbourne. To accommodate a rapidly growing population, Melbourne’s built environment and natural environment will continue to change at an exponential rate. On a 30 degree Celsius day in Melbourne, the CBD is 0.8 degrees Celsius hotter than non-CBD areas.
Architecturally, Melbourne is known for its iconic bluestone paths, dark glass and concrete facades. Addressing UHIE while retaining Melbourne’s unique identity is a complex challenge.
In response to complex challenges of UHIE, the Victorian government has identified the importance of green and blue infrastructure. They have developed the Cooling and Greening Melbourne (2017-2020) initiative, with the Victorian Department of Environment, Land, Water and Planning working together with RMIT University, CSIRO, and the Clean Air and Urban Landscapes (CAUL) Hub to map and analyse vegetation, land use, and urban heat across Melbourne. This initiative has created interactive spatial maps.
5. Learning from South Australia after the 2009 heatwave
Accepting scientific evidence
South Australia is making strides to curb UHIE. The January-February 2009 heatwave is most well-known for accompanying the devastating Black Saturday bushfires in Victoria, which tragically took the lives of 173 people. Less well known is that the heatwave is estimated to have resulted in an additional 374 deaths in Victoria and 32 deaths in South Australia.
In response to this and other heatwaves, the South Australian Southern Region Local Government Implementation Plan 2015-2019 has developed the South Australia Urban Heat Mapping initiative. This is a monitoring platform that uses thermal imagery to measure land surface temperatures of urban areas and identify hot spots.
The South Australian state government proposed amendments to their 30-year Adelaide Development Plan in 2017, which promotes green infrastructure to reduce building energy use and improve biodiversity. Initiatives include adopting green roofs, vertical gardens and water sensitive design in higher density and mixed-use developments to assist with urban cooling. At Adelaide Airport, water for irrigation and toilet flushing now comes from a wastewater treatment plant, and a stormwater harvesting scheme is already in place to service future airport developments.
The two-year trial has shown the irrigated land was more than 3? cooler than non-irrigated lands.
6. Learning from Singapore
Solutions to UHI: Accepting scientific evidence
Presently, Singapore is nearly 100 per cent urbanised, with a population of over 5.6 million growing at a rate of 1.2 per cent (Dept of Statistics Singapore, 2019), accommodated in an area just over 720 square km – slightly smaller in metropolitan area than Canberra (approximately 814 square km). Projections estimate that by 2030 Singapore will be home to 6.9 million people, requiring Singapore to expand to 760 sq km (Cheam, 2013, Ministry of Trade & Industry, 2013).
During summer, the temperature can be up to around 7? higher in the central business district than in other surrounding districts (Chow & Roth 2006, Cooling Singapore 2018). The 2030 projections of more people and increase in buildings and infrastructure is certain to fuel UHIE on the island.
Singapore has actively reduced its carbon dependency since ratifying the Paris Climate Agreement in 2016. Actions include switching from carbon fuel oil to natural gas and other diverse power sources, and investment the more efficient and affordable public transport to achieve a car-lite city.
The government-funded ‘Cooling Singapore’ project has seen government agencies working collaboratively with local and international researchers to develop strategies to reduce UHIE and improve outdoor thermal comfort. Their aim is to ultimately provide a “whole of nation”, coherent approach that acknowledges and works with Singapore’s tropical context.
This means Cooling Singapore is collaborating with local councils and agencies that manage buildings, land use, parkland and waterways, and transport and energy infrastructure to understand the drivers of UHIE in each “Local Climate Zone”.
Each district profile provides information on material types, colour and coverage; urban shading patterns; transport mobility patterns; blue-green-grey ratios and distribution; urban geometry of block and district building landscapes as well as energy use profiles.
Specifically for the building sector, the Urban Redevelopment Authority’s LUSH (Landscaping for Urban spaces and High-rises) program was launched in 2009 (URA 2017) to increase skyrise greenery. Currently, parks, nature reserves and reservoirs occupy 13 per cent of land use (URA 2013 as cited by Zhou & Zhao 2016).
In order to increase the amount of green and blue infrastructure on the small island, the Building Control Authority has mandated inclusion of greenery on roofs and on upper levels of buildings or on walls. In response, architects and developers have turned their skills to creating cooling designs, which encourage biodiversity too.
Successes: Urban greenery at multiple levels is already creating a more beautiful and greener city. This is acting as a temperature regulator, supporting community urban farms as well as providing health and well-being benefits to its residents.
Singapore’s experience and success shows that it is not the sole responsibility of the government, nor the building sector or landscape sector, to mitigate the impacts of UHI effect.
All stakeholders must come to the table to collaborate, innovate and provide opportunities to rethink traditional urban solutions, implement, monitor performance and future proof the health of residents and the longevity of natural and built assets in the face of increasing heat.
Dr Mittul Vahanvati is lecturer and research fellow at RMIT University, the School of Global, Urban and Social Studies. Her research and practice focuses on long-term effectiveness of disaster recovery, which sits at the intersection of environmentally sustainable buildings and community resilience. She specialises in co-production approaches and designing reconstruction programs for long-term community resilience and has been based in Australia, Switzerland and India..
Dr Adriana Keating is a Research Fellow in the Centre for Urban Research. Her research focuses on the human dimensions of disasters and climate change adaptation. She is an expert in disaster resilience, and her work utilises systems analysis, and measurement and decision-support methodologies.
Helen Cheng is a practising Australian architect in Singapore, studying Masters of International Urban and Environmental Management, focusing her research on Singapore building practice, strategies and policy implementation.
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