Climate change

Our global climate is changing (see the Climate chapter). Temperatures are increasing, rainfall patterns are changing, sea levels are rising, and the frequency and magnitude of extreme weather events are increasing (IPCC 2018).

Our changing climate and the associated increase in extreme events have a significant impact on the safety, health and wellbeing of citizens and biodiversity, the durability of our built infrastructure and the resilience of our urban ecosystems.

Indigenous communities, both urban and remote, as with other marginalised communities, are disproportionately affected by many aspects of climate change. (For more on the effects of climate change on Indigenous communities, see Indigenous built environment) (see the Climate and Indigenous chapters).

Urban heat

The impact of rising temperatures and the increasing frequency of heatwaves is a growing challenge for urban areas. Rising temperatures particularly affect cities because of the ‘urban heat island effect’, in which urban areas are warmer than the surrounding land. This is a result of the presence of roads, pathways, buildings and dark roofs that trap and absorb heat more than green (e.g. gardens and parks) and blue (e.g. rivers and creeks) surfaces.

With the urban heat island effect, temperatures in our urban areas can be 1–7 °C higher than in surrounding areas. Research in Adelaide found a difference in temperatures between urban and rural areas of 5.9 °C (Soltani & Sharifi 2017).

These notable differences are expected to become even more pronounced with climate change. The Intergovernmental Panel on Climate Change estimates that ‘even if global warming is restricted to below 2 °C, there could be a substantial increase in the occurrence of deadly heatwaves in cities if urban heat island effects are considered’ (IPCC 2018). This will have significant implications for our urban areas.

Forecasts reported in the 2016 state of the environment report remain the same in 2021:

CSIRO and BoM projections of the average number of days per year with maximum temperature above 35 °C in 2030 (Table 18) for the future Representative Concentration Pathways (RCPs) increases considerably, particularly in northern areas of Australia and at some inland urban areas with greater warming (e.g. Canberra airport). By 2090, the number of days above 35 °C shows a moderate increase for some cities under the RCP2.6 scenario, and numbers increase significantly for most cities under the other 2 scenarios. (Coleman 2016:32)

Impacts on livability and wellbeing

Urban heat significantly affects livability. Recent analysis shows that increased exposure to higher temperatures (generally more than 28 °C) (WSROC 2018) results in negative impacts, including on sleep, health, crime, income and labour productivity (WSROC 2018). These impacts are particularly apparent during heatwaves, which are defined by the Australian Bureau of Meteorology as a period of 3 or more consecutive days of high maximum and minimum temperatures. The impacts are most severely felt by the most vulnerable – older people, children and those with existing medical conditions.

Heatwaves can worsen existing illnesses (morbidity) and can cause death (mortality; Figure 13). In fact, heatwaves kill more Australians than any other natural disaster – they are more deadly than storms, fires and floods combined (WSROC 2018). According to the Western Sydney Regional Organisation of Councils (WSROC), between 1987 and 2016 in Australia, more than 500 people lost their lives as a result of heatwaves and a further 2,800 were injured (WSROC 2018).

Heat contributes to the deaths of more than 1,000 people aged over 65 across Australia each year, with some sources identifying excess heat as contributing to as many as 1.7 million deaths between January 2006 and October 2017 (Longden 2020). This pressure is forecast to grow (Figure 13), and is particularly concerning in the context of Australia’s ageing population (Wilson et al. 2011).

The WSROC action plan identified that heat-related illness is likely to worsen with climate change, as is the risk of respiratory problems. The action plan states that ‘extreme heat exacerbates air quality issues such as pollution from vehicle emissions, industrial fumes and bushfires as well as increased ground-level ozone and dust and pollen levels’ (WSROC 2018:25).

Many desert-based Indigenous communities are experiencing such extreme heat that they are unable to continue to live in their own Country during certain times of the year, creating disruption to community governance and cultural practices.

Impacts on infrastructure and landscape

Heat and heatwaves place significant pressures on our infrastructure and resources such as energy and water. Residential electricity use can be 3 to 4 times higher than normal on days that are 35 °C or hotter, placing stress on the power grid (WSROC 2018) and increasing the risk of blackouts or power shortages. These have a potentially more significant impact during a heatwave by increasing the likelihood of death when vulnerable communities are left without air-conditioning. WSROC identified that the ‘continuity of energy supply is often the difference between life and death in a severe heatwave’ (WSROC 2018:25).

Increasing levels of heat also affect the natural environment. Changing climates can lead to shifting habitat zones and breakdowns in crucial ecological cycles. These shifting habitat zones, combined with the loss of habitat due to an increase in development, can have tremendous impacts on the health of animals and plants in the natural environment. Increased heat can also have a significant impact on household pets (WSROC 2018).

Effects on green cover are of particular concern because increasing green space is one means of mitigating the exposure of urban citizens to heat. The Clean Air and Urban Landscapes Hub report, Risks to Australia’s urban forest from climate change and urban heat, found that, by 2070, 14% of all public trees (22% of species) in Australian cities are at high risk from increased temperatures in the emissions-limited climate change scenario, and 24% of all public trees (35% of species) in the business-as-usual emissions scenario (CAUL Hub 2017).

Bushfires

Bushfires are natural events in Australia and many native species have evolved to rely on fire for regeneration. Indigenous people have used fire for thousands of years to manage Country. The removal of Indigenous people from the land, and landowners then adopting a non-Indigenous land management framework, has contributed significantly to the occurrence of extreme fire events (Fletcher et al. 2021).

Since the 1950s, records show that the frequency and duration of extreme fire weather across large parts of Australia has increased, especially in southern Australia. Climate change is a major contributor to this trend because increases in temperature and reductions in rainfall and atmospheric moisture content increase landscape drying. We are seeing an increase in the annual number of extreme fire danger days across Australia. In addition, increased levels of carbon dioxide in the atmosphere can increase plant growth, thus increasing the amount of fuel in the environment.

Bushfires can threaten urban areas, particularly those near the urban fringe or vegetation corridors. For example, the bushfires in the south-east of Australia during the 2019–20 summer destroyed 3,094 houses (Parliament of Australia 2020). Other urban areas and cities such as Canberra were heavily affected by the smoke, which travelled many hundreds of kilometres from the fires (see the Air Quality chapter).

Indigenous cultural fire management knowledge is being sought by landowners, and is employed to varying degrees across Australia. This practice is being investigated as part of a wholistic land management approach (see the Extreme events chapter).

Rainfall deficiency and drought

Australia is the driest inhabited continent (DAWE 2021). With Australia’s changing climate, rainfall patterns are also changing, with some parts of the country expected to spend more time in drought (and a greater intensity of drought), which will affect water reliability for our urban areas (see Water).

For example, between early 2017 and mid-2020, much of Australia experienced significant drought conditions. As of December 2019, Australia was experiencing some of its lowest levels of rainfall on record. Regions affected include South East Queensland, pastoral South Australia, most of south-west Western Australia, and much of the Northern Territory and central Australia (BOM & CSIRO 2020) (see case study: The 2017−19 Australian drought, in the Drought events and trends section in the Climate chapter). During this time, river levels fell, water storage significantly decreased and soils became drier, reducing agricultural productivity and the livability of communities across Australia. The significant water shortages placed noticeable strain on urban areas, necessitating water restrictions. In some regional areas, water security became such an issue that water needed to be trucked into towns.

Extreme rainfall and flooding

While rainfalls across the southern parts of Australia have been well below average levels in recent years, Australia still experiences severe rainfall events due to natural climatic cycles. Climate change is also increasing the likelihood of extreme weather events such as heavy rainfall (BOM & CSIRO 2018). With climate change, ‘the intensity of short-duration yet extreme rainfall events has increased by around 10% or more in some regions and in recent decades’ (BOM & CSIRO 2020). This is especially true in the northern parts of Australia.

One of the main natural climate cycles is the El Niño–Southern Oscillation, which alternates between La Niña and El Niño patterns. La Niña causes increased rainfall across much of Australia, cooler daytime temperatures (south of the tropics) and warmer overnight temperatures (in the north). According to Bureau of Meteorology data, in eastern Australia, the average December–March rainfall during La Niña years is 20% higher than the long-term average, with 8 of the 10 wettest periods occurring during La Niña years. While this can be a positive for agricultural production, this also increases the likelihood of severe flooding threatening urban areas during La Niña summers, as experienced along the east coast of Australia in 2021.

La Niña also results in earlier onset of the monsoon season and a greater likelihood of cyclones earlier in the season. In fact, historical trends show that twice as many cyclones will make landfall during La Niña years as during El Niño years. Furthermore, the only years with multiple severe tropical cyclone landfalls in Queensland have been La Niña years. This means an increased likelihood of major damage and flooding related to strong winds, high seas and heavy rains (BOM & CSIRO 2020) for most of our urban environments that are located along the eastern seaboard.

This climatic outlook has placed several urban areas on notice. Flooding will particularly affect those built close to waterways, in low-lying areas and where there is a large amount of impervious groundcover (e.g. concrete pavements or bitumen roads). For example, Western Sydney has a high probability of flooding owing to its topography.

Flooding is also a challenge for many Indigenous communities, whose urban environments are often built on the outskirts of urban areas or on land that was not claimed by others because it is liable to flood. Many Indigenous communities may experience multiple evacuations over the course of the year, disrupting employment and education routines that are often already inconsistent. Many lower socio-economic urban areas may also be at greater risk because they can have less green cover, so less water can be absorbed by the soil (see Green cover).

Sea level rise

Sea levels are rising because of climate change. The warmer ocean waters are expanding, and ice in the higher latitudes is melting. The rate of change is accelerating. Combined with more frequent and severe storms causing storm surges, this creates an increasing risk of coastal erosion, shoreline recession, and permanent or more frequent inundation of low-lying coastal regions and estuaries. This will damage coastal infrastructure and communities (see case study: Sea level rise and the Torres Strait islands, in the Impacts of sea level rise section in the Climate chapter).

Sea level rise and associated impacts will affect not only the natural environment, but our urban infrastructure, food security and human health. It is estimated that the value of housing and infrastructure at risk from sea level rise in Australia exceeds $226 billion (DCCEE 2011).

This is significant because most Australians live near or on our coasts: 7 out of Australia’s 8 capital cities are on the coast and only 4 of the 18 cities with populations greater than 100,000 are located inland. In fact, it is estimated that 80% of Australia’s population lives within 50 kilometres of the coast (Cechet et al. 2011). Since 2016, the coastal urban population has increased, spreading particularly into the south-west of Western Australia, around Darwin and areas surrounding Australia’s capital cities (i.e. Geelong, Newcastle, the Gold Coast).

As Coast Adapt (2017:1) states, ‘the Torres Strait is a region of national and international significance for its cultural and environmental values. The region faces a number of climate change risks, most notably the impacts of progressive sea level rise. Coastal erosion and inundation have been pressing issues for a number of communities for many years’ (CoastAdapt 2017).

Adaptation

The urban planning profession has been calling for an integrated national response from all levels of Australia’s governments to better manage current and future urban development and land use via a national coast plan or strategy (Infrastructure Australia 2020a). Experts have also called for the restoration of national funding for coastal planning and management research to better support and prepare coastal communities and assets to address the adverse effects of climate change (House of Representatives 2009, ACCA 2019). Hazard and inundation mapping are underway for most developed sections of the Australian coast. This will enable governments to better appreciate the scale of infrastructure and private properties at risk as sea level continues to rise.

However, to truly address these pressures, we need to change where we build and adapt what we have built along our coasts. Options include:

• retreat, by which houses or infrastructure are moved out of the impact zone
• accommodation, such as raising floor levels (Table 19)
• protection, which includes hard engineering structures, such as seawalls and groynes, and a range of softer engineering options, such as beach nourishment or replenishment, beach scraping and dune management.