Consequences of a changing climate
Climate change is already beginning to affect our society by altering the climatic conditions on which we have built our industries and infrastructure, including through increased frequency of adverse weather events, such as extreme heat and heatwaves. These impacts are predicted to continue and intensify in the future, affecting our health, economy and infrastructure.
It is also affecting the natural ecosystems on which we rely for essential services and enjoyment. Our vulnerability to climate-change impacts ultimately depends on our exposure and sensitivity to the changes or events and our capacity to adapt. In this globally interconnected world dependent on intricate supply chains, Australia and SA will also be affected by climate-related impacts in other parts of the world.
Extreme weather events have direct and immediate impacts, but slower changes in the climate, while less dramatic, can also have serious consequences. Slow changes in climate can create background stresses that increase our vulnerability to non-climate events.
Australia is considered one of the most biologically diverse countries in the world, with many species unique to the continent. Biodiversity is a critical part of our life-support system, providing regulation of air and water quality, climate regulation, and erosion, pest and pollution controls, as well as providing genetic resources for medicines, food, fibre and fuel.
Maintaining biodiversity and healthy ecosystems is also important to assist with adaptation in other sectors, such as coastal wetlands protecting human infrastructure from storm surges.
Climate change will exacerbate existing stresses on our natural systems, including habitat loss and fragmentation, introduced species and pollution. The impact on natural systems will extend beyond rainfall and temperature to changes in ecological processes influenced by altered hydrological and fire regimes. Some projected changes may occur incrementally as average climatic conditions gradually shift, while other changes could occur far more abruptly as a result of extreme weather events.
Many species are projected to suffer considerable reductions in available climatic habitat in the future, even when incorporating optimistic migration assumptions into species distribution modelling. Some species may suffer complete loss of habitat, which would greatly increase their risk of becoming extinct. The mortality of many different plants and animals during recent droughts and heatwaves has already been observed and well-documented in Australia.
Whole ecosystems are succumbing to climate disruption. In 2016, unusually dry and hot conditions triggered massive fires in Tasmania’s World Heritage forests while ocean circulation patterns have moved unprecedented underwater heatwaves around the world, driving the tragic coral bleaching of the Great Barrier Reef and the mass dieback of mangroves along the Gulf of Carpentaria. More than 45,000 flying foxes were killed on one unusually hot day in south-east Queensland in 2014. – Professor Will Steffen
Potential impacts on SA species and ecosystems may include changes in distribution and abundance, population dynamics, life history patterns and reproductive cycles. Vulnerable species might be at increased risk of extinction, and invasive and overabundant native species might gain more opportunities for establishing in wider areas. Land-based species and ecosystems in the Mount Lofty Ranges and Kangaroo Island are likely to be the most vulnerable.
Coasts and marine environments
Changes in sea levels and their extremes, sea surface temperatures and ocean pH have the potential to affect both coastal terrestrial and marine environments.
Rising sea levels result in a greater coastal flood and erosion risk. Rising average sea levels mean extreme sea levels of a particular height are exceeded more often during storm surges. A 10-fold increase in the frequency of extreme sea levels at many locations is projected by 2100, even for a low emissions pathway. Ocean thermal expansion and melting ice caps and glaciers are the main contributors to global mean sea-level change. In line with global mean sea level, Australian sea levels are projected to rise at a faster rate through the 21st century than over the past 4 decades and continue to rise beyond 2100 under all greenhouse gas emission scenarios.
For locations along the SA coastline, mean sea levels are expected to rise from 0.1 metre by 2030 to 0.38–0.61 metre by 2090, depending on the emissions scenario, relative to the period 1986–2005. However, it is possible a larger sea-level rise of several tenths of a metre could occur by late in the century as a result of an instability of the marine-based West Antarctic ice sheet. Extreme sea levels are also expected to increase due to increases in regional sea level and changes in climate and meteorological events.
Sea level in SA has been rising around 4.5 mm per year since the early 1990s (Figure 16 and Table 9). This is exacerbated in Port Adelaide (an area of major economic importance), where land is also subsiding at a rate of between 1.3–2.1 mm per year.
Table 9: Fraction of coastline susceptible to recession under sea level rise, defined as shores composed of sand and mud, backed by soft seditment (so that recession is largely unconstrained), and shores composed of soft rock. Based on data from DCC (2009).
|State||Total length of open coast (km)||Total length of vulnerable coast (km)||Proportion of vulnerable coast (%)|
|New South Wales||2,109||839||40|
From: Cranking up the Intensity: Climate Change and Extreme Weather Events by Professor Will Steffen, Professor Lesley Hughes, Dr David Alexander and Dr Martin Rice (Climate Council 2017)
Sea surface temperature
Sea surface temperature (SST) in the upper ocean (from the surface to 20 m below) has significantly warmed over the last 5 decades. This is projected to increase around Australia under all emissions scenarios. Marine biodiversity is likely to be impacted through southward shifts in some marine species and local extinction for others.
In addition to absorbing over 90% of the additional heat arising from the enhanced greenhouse effect, oceans have played a key role in reducing the rate of global climate change by absorbing about 30% of the CO2 released by human activities over the last 200 years, thereby increasing their acidity.
Ocean acidification is likely to have an impact on the entire marine ecosystem from plankton at the base of the marine food chain to fish at the top. Acidification affects reproductive health, organism growth and physiology, species composition and distribution, food-web structure and nutrient availability. Ocean acidification also impedes the shell formation by organisms such as corals, oysters, clams, lobsters, crabs, starfish and some plankton.
Such changes, already detectable in plankton in the Southern Ocean, are expected to have serious impacts on key marine species, aquaculture, fisheries and other marine industries.
Projected climate change impacts on SA’s highly diverse marine environments are likely to be large and negative. Seamounts and inverse estuaries (such as the Spencer Gulf where the water is more saline than the open ocean) could be subjected to corrosive waters precluding or reducing the occurrence of many calcareous species, such as molluscs, and the larval stages of all commercial species.
Increases in ocean temperature are causing the range of several species of kelp to contract southwards and, in some cases, these species are disappearing altogether from coastal waters close to Adelaide. The combined impact of ocean warming and acidification on kelp is predicted to be profound.
The Great Australian Bight is a region of high marine and coastal biodiversity, and many species will be affected by the projected weakening of ocean currents and increased ocean temperatures.
The endemic Australian Sea Lion, 80% of the population of which occurs in SA, is a non-migratory animal at high risk from climate change as a result of reduced food availability and increased risk of disease, due to rising temperatures and habitat disruption.
The Leafy Sea Dragon, SA’s marine emblem, is likely to suffer from storm events and habitat degradation caused by ocean warming, acidification and sea-level rise. Coastal ecosystems, including internationally significant bird species, are likely to be impacted by sea-level rise, storm surges and reduced rainfall.
A risk assessment of SA’s 10 most valuable wild fishery and aquaculture species has indicated 4 of these (Southern Rock Lobster, Blacklip and Greenlip Abalone, and King George Whiting) are at high risk from potential climate-change impacts.
The SA coastline has two gulfs that are zones of upwelling. Upwelling brings nutrients from the deep ocean to shallower waters, providing food for marine ecosystems. Effects of climate change on the marine environment may lead to changes in the frequency and intensity of upwelling events, potentially affecting food availability for Southern Bluefin Tuna and the abundance of sardines. Other stressors, such as overfishing, pollution, habitat loss and disease are likely to exacerbate the threat from climate change.
Climate change is already presenting direct and indirect risks to human health. These will escalate in the coming decades if climate change continues on its current trajectory. More frequent and intense heatwaves, other extreme weather events and disasters, such as floods, storms and bushfires can cause death, injury or ill health. Indirectly, climate change affects human health through impacts on food production and natural ecosystems on which we rely. Economic stress and displacement increases mental health problems and conflict.
Humans can only survive when their core body temperature remains within a narrow range of around 36.5°C to 37°C. Our ability to cool ourselves through sweating is reduced in humid conditions. Climate change has significantly worsened recent extreme heat events in Australia and across the globe.
A global average temperature increase of 1 or 2°C does not simply translate into modest, uniform warming, but rather triggers surprisingly sharp changes in extreme weather and disrupts longer-term weather and climate patterns. A few degrees increase in the average temperature leads to a dramatic escalation in the risk of extremely hot temperatures, lasting for longer periods of time. When average temperatures increase, the whole distribution of temperatures shifts, resulting in a large percentage increase in the extremes.
Prolonged and extreme heat over SA occurred in the summer of 2016–17. While the commonly cited January 1939 Australian heatwave is one of the most significant in recorded history, the frequency of such intense large-scale heatwaves has increased across spring, summer and autumn, and especially over the last 20 years.
The penetration of a tropical air mass in December 2016 saw high temperatures, heavy rainfall and exceptionally high levels of humidity affect a wide area of Australia, and SA recorded its wettest December on record. Extreme heat affected much of southeastern Australia in December 2015, with numerous temperature records broken in SA.
Across SA, average minimum temperatures were the highest on record. A significant multi-day heatwave persisted in January 2014, breaking numerous records for extended periods of heat and hottest days in some locations. Adelaide’s temperature reached 45.1°C, the 4th occasion in the last 5 years on which it has reached 45°C. Adelaide also set a record with 5 consecutive days of 42°C and above.
Urban heat island effect
Urban areas are significantly hotter than their rural surrounds, making them particularly dangerous places during heatwaves. The main causes of the urban heat island (UHI) effect are changes to the land surface by urban development and the concentrated generation of waste heat by vehicles, air conditioning and industry.
Roads, buildings and other structures contain solar-radiation absorbing materials, such as asphalt and concrete, causing surface and ambient temperatures to rise. Built infrastructure has also displaced trees and other vegetation, reducing the effects of shading and the cooling effects of evapotranspiration from leaves and soil. Buildings and narrow streets block airflow, preventing the escape of retained warmth.
The UHI effect has serious implications for human health and productivity, which will be exacerbated as the climate warms. The effect also increases energy requirements for cooling, leading to an increase in greenhouse gas emissions. Efforts to reduce the UHI effect are important adaptive and mitigation responses.
Urban–rural temperature differences start to develop during the day and emerge more strongly under clear skies due to the maximum chance of solar heating. Heat mapping of the Adelaide metropolitan area indicates heat accumulates during the afternoon in the built environment and is discharged to the atmosphere with delay during the night.
The recorded UHI effect in Adelaide1 reached a maximum of 5.9°C at midnight during a typical winter day. While the magnitude of urban–rural temperature differences is usually reported to be higher at night-time, maximum urban heat stress occurs during the afternoon when both temperature and daily urban heat are at their peak.
Spatially, heat islands vary significantly in magnitude according to small-scale urban features. The central business district (CBD) is the leading hot spot despite the surrounding parklands providing a cooling effect. In summer, the presence of sea breezes dominate temperature variations, but the effect diminishes as it progresses inland. When sea breezes are absent, concrete-laden suburbs with high heat retention, such as areas along Main South Road, are the warmest.
Suburbs with extensive urban tree canopy cover are generally 2°C cooler than suburbs with less canopy cover. Even within the city CBD, the UHI effect is clearly exhibited, whereby the area with the highest buildings and hence the largest heat storage capacity is hotter during low-wind and clear-sky conditions. Open spaces like Victoria Square display lower temperatures.
The addition of trees and vegetation in the built environment is one of the most effective ways of reducing the UHI effect. Green spaces should be irrigated where possible to maximise cooling. Increased infill across metropolitan Adelaide will exacerbate development of heat islands if sufficient strategies are not implemented. Green space and tree cover should be at least maintained. Other strategies for minimising the UHI effect include:
- narrowing the carriageway of main roads
- using lighter coloured road pavement
- planting vegetation alongside infrastructure for shading and cooling
- using highly reflective building materials and materials with a high thermal resistivity
- using light coloured roofs in residential and industrial areas
- reducing production of heat generated through human activities.
The 202020 Vision is a national collaboration of organisations working together to create 20% more and better urban green space by 2020.
Agriculture is a significant contributor to the SA economy and national food production, and is highly sensitive to variations in climate. In 2015–16, the grains industry generated $4.4 billion in revenue and the livestock industry generated $4.8 billion. South Australia produces almost half of the nation’s wine grapes and over 57% of national wine exports.
The projected warming and drying trend for SA’s cropping zone during the growing season may bring less reliable grain production and less crop biomass to protect soils from erosion. A reduction in available crop biomass will impact the long-term sustainability of agricultural land, associated farm enterprises and food security in SA.
Increasing temperatures are likely to have adverse effects for cattle and sheep and reduce overall productivity in the beef, sheep and wool sector.
Since 1997, SA’s agricultural regions have experienced a marked decline in growing-season rainfall. The range of adaptation strategies for primary producers is large and includes breed, grain and grape selection, water conservation, soil erosion protection and changes to the timing of farm operations. In the short term, adaptation responses are consistent with current best practice. However, there are limits to adaptation, and more transformational change to adopt different landuse and management practices is likely to be required over the longer term.
Regional communities are disproportionately affected by the impacts of climate change. Economic activity and livelihoods in rural areas are closely linked to natural resources and are particularly sensitive to droughts, floods, heatwaves and bushfires.
Agriculture remains the key economic foundation of many rural communities and climate change will also impact on these communities via effects on fisheries, forestry, mining and tourism. Rural landholders and communities play a vital role in Australia’s food security, water supplies and prosperity, providing about 93% of the country’s domestic food needs and over 13% of export revenue.
In addition to affecting agricultural production, climate change threatens to increase the cost of essential goods and services. Those living in rural communities are also more directly exposed to climatic impacts such as extreme heat and water shortages, diminishing the liveability of exposed rural areas. Climate change is also exacerbating existing vulnerabilities, such as already high levels of debt, high unemployment rates, mental health issues and reduced access to health services.
Climate change is already affecting rural communities, with some having to deal with multiple extremes at once or in rapid succession. The direct impacts of climate change have flow-on effects in small communities.
The myriad of challenges climate change poses for rural communities in an already difficult operating environment should not be underestimated. The sustainability, health, liveability, productivity and prosperity of our rural and regional industries, landscapes and communities require a strong commitment to policies and practices to assist in coping with climate change.
While rural communities are well practiced at adapting to a highly variable climate and volatile economic conditions, such resilience is not universal. All adaptation approaches have limits, both biological, such as extreme temperatures exceeding thresholds, as well as institutional, technological, informational and economic.
Adaptation options to reduce climate-change risks include generic actions that aim to strengthen resilience of a region by improving existing systems and services and the management of uncertainty. Specific adaptation measures range from ‘incremental’, such as progressively altering sowing or harvesting dates and changing crop varieties or livestock breeds, to the more transformational, such as changing production systems or relocation. Lack of financial resources is preventing many landholders from preparing for climate change.
Rural communities can also play a key role in reducing Australia’s greenhouse gas emissions. Ruminant animals like cows and sheep are the largest single source of agricultural emissions, producing large amounts of methane from food digestion.
Opportunities for reducing methane emissions are currently the subject of significant research effort. Revegetation of cleared land, biochar production and alternative biofuels provide other opportunities. Renewable energy projects contribute enormously to reducing our greenhouse gas emissions. They can be co-located with grazing and cropping activities, provide direct income to landholders and local shires and create a variety of flow-on business, employment and training opportunities.
The effects of climate change, including prolonged extreme heat, sea-level rise, changes to rainfall patterns and more intense extreme weather, is likely to affect almost all types of major infrastructure, including ports, commercial and residential buildings, transport systems and utilities.
Coastal buildings and infrastructure are particularly vulnerable and, with much infrastructure concentrated in the coastal zone, this has consequences for the delivery of essential services and regional economies. In SA, between 26,000 and 46,000 commercial, residential and industrial buildings currently worth from $28–$36 billion, and an estimated $7 billion worth of road and rail infrastructure are at risk of inundation from a 1.1-m sea-level rise this century. The level of this risk will be reduced by existing and future coastal protection, such as seawalls and dune systems.
The total economic costs of the 2014 SA bushfires has been estimated at $44 million. Much of our existing infrastructure has not been designed to withstand the expected impacts of more intense extreme weather events. It will be a major challenge to adapt existing infrastructure to expected climatic changes and the financial costs of doing so will be high.