Number of days over 35°C in Cairns
Figure 4. Number of days over 35°C under ‘Business as usual’ emissions scenario (MIROC5 climate model) http://www.climatechangeinaustralia.gov.au/en/climate-projections/explore-data/threshold-calculator/.
Sea level rise in Cairns
Figure 5. Increased height needed to maintain the current level of exposure of assets to flooding from high tides & storm surges, under ‘Business as usual’ emissions scenario, https://www.climatechangeinaustralia.gov.au/en/climate-projections/coastal-marine/marine-explorer/#.
People in the Cairns local landscape know that rainfall, temperature and cyclones vary from year to year, but that our ability to live in and manage the landscape is based on long experience of general seasonal patterns. However, knowledge based on past experience is becoming less reliable as temperatures and sea levels rise and extreme weather events become more common. The science is telling us:
- Less predictable weather: Temperatures are already increasing in our region, but more importantly, the predictability of our weather patterns is changing. It will become increasingly difficult to rely on our past experience to make decisions about where to build houses and infrastructure, which crops to grow, which pests and diseases to target, and how to manage fire. Access to reliable information will help guide decisions.
- Climate change and industries: Industries in the Cairns Local Landscape, like tourism and agriculture, will be affected by climate change. This is likely to have flow-on effects on the region’s economy.
- Climate change and communities: While climate change, particularly rising temperatures and sea levels, will have implications for communities and infrastructure, being informed about the types of changes likely puts us in a better position to plan, prepare and develop strategies.
- Climate change and natural systems: The additional pressure of climate change on natural systems may require us to build ‘new knowledge’ to better understand the complex management requirements of our natural areas and ensure they continue to thrive.
There are opportunities for everyone to get involved in shaping a resilient and sustainable future for the Cairns region. For more information on climate change, including links to more detailed climate change modelling for our region, go to the Climate Futures page.
Long-term temperature records from the Cairns airport show that average temperatures have been on an increasing trend over about the past 20 years, and that during this time, average annual temperatures in the Cairns region have been above the long-term average much more often than they have been below it (Figure 1).
Long-term rainfall data from the Cairns airport show that rainfall continues to vary dramatically between years, and that there is no obvious increasing or decreasing trend in annual rainfall at this stage (Figure 2).
As time goes on, higher temperatures will be reached more frequently. For example, maximum daily temperatures during January are projected to increase from the current average of 31.6°C to 33.1°C by 2030, 33.2°C by 2070 and 34.5°C by 2090 (Figure 3). Furthermore, there will be a longer season of high temperatures, with average daily maximum temperatures exceeding 30°C in 2090 from September to May, rather than from November to March as is currently the case.
While we are likely to see an increasing trend in temperatures as a result of climate change, one of the most concerning predictions coming from climate scientists is the impact of greater variability and less predictability in our weather patterns, making it harder to plan.
As the retail, transport and supply hub for far north Queensland, climate change impacts on associated industries and services will affect the area’s economy. Very hot days, heat waves, cyclones and floods all have the potential to result in shut down of industrial processes, either through workplace health and safety concerns, power failure, flooding or damage. For example, the Cairns International Airport is located in a very low-lying position in the landscape and will become increasingly vulnerable to high sea level events. Operation of Cairns’ sea port will also be affected by higher storm surges, more intense cyclones, more frequent flooding during heavy rainfall, and more extreme heatwaves. Considering the importance of the port to both the import of fuel, food and other supplies, as well as to the export of regional produce, more frequent closures are likely to have significant economic – as well as social – implications for the region.
In the Cairns region, grazing and cropping will be directly affected by increasing average temperatures, evaporation, heat waves, seal level rise and extreme rainfall. For example, the sucrose content of sugarcane can decline if temperatures are high and/or there is high rainfall during the ripening and harvest season. Areas of agriculture in low-lying coastal areas will obviously be vulnerable to sea level rise, either through sea water inundation, increased tidal reach or salt-water contamination of coastal aquifers.
Climate change will also impact the commercial fishing industry. People in the Cairns area have experienced the impacts of intense cyclones, with several months of lost operations due to large amounts of debris or sediment in the water, as well as damage to boats, marinas, ramps and other infrastructure. Commercial fishing operations will also be affected as certain types of fish move south due to increasing water temperatures, as coral bleaching becomes more widespread and as conditions decline in fish breeding and nursery areas.
Tourism in the Cairns landscape is underpinned by the natural values of the area, especially the Great Barrier Reef and mainland world heritage forest areas. Climate-induced changes in the health and composition of natural systems (see below) will potentially have major impacts on tourism in the Cairns area. Since tourism is already very seasonal, prolonged hot weather and less predictable rainfall is likely to affect visitation patterns to the region, while more extreme weather may influence tourists’ perception of their safety in the region.
Doing things the way they’ve been done for generations won’t necessarily keep working as climate conditions continue to change, meaning that traditions and local wisdom will be challenged. Everyone will be affected in one way or another by climate change: some types of farms may not remain viable, certain areas along the coastline may become unsafe to live, and some of our iconic species may not survive in the new conditions. While change can be unsettling, new opportunities may come out of new ways of doing things, especially by working together across sectors and industries. Importantly, being informed about the types of changes we can reasonably expect means that we can develop plans and strategies to adapt to these, rather than being taken by surprise by unusual climate events.
Although people in the Cairns area are used to living with high temperatures, we can expect that periods of extreme heat will become more common and even hotter. For example, the number of days hotter than 35°C in Cairns is projected to increase from the current average of four, to eleven by the year 2030 (and to eighteen by 2050) under the ‘business as usual’ emissions scenario (Figure 4). More people will be vulnerable to heat-related illnesses and stress, especially sick, elderly and very young people, and people living without air-conditioning.
In the same way that maximum temperatures are increasing (Figure 3), minimum temperatures are also rising. This means that overnight temperatures will remain above 20°C for more months of the year, potentially affecting sleep quality, especially for households without air conditioning, and increasing the use of air conditioning in households with it.
Sea levels are already rising and models project that sea levels in this region will increase by an average of 0.14 m by the year 2030, and by an average of 0.65 m by 2090 under a business as usual emissions scenario. By 2030, homes and other assets on the Cairns delta system would need to be 0.14 m higher (and by 0.79 m in 2090) to maintain their current level of exposure to flooding from the ocean (Figure 5). Low elevation areas of the coastline will be most vulnerable.
Rising sea levels will increase the tidal extent of coastal rivers and streams, meaning that the tidal reach in the Mulgrave and Barron Rivers may push further upstream, potentially affecting homes, businesses and crops on adjacent floodplains, as well as roads and other infrastructure. Even a modest increase in sea level height will mean that there are many more high tides and storm surges, increasing coastal erosion, flooding and contaminating freshwater systems with salt water. The CoastAdapt tool (https://coastadapt.com.au/) helps people making decisions in coastal areas to understand and asses the risks posed by climate change in their regions.
The impacts of sea level rise will be compounded by more frequent and intense heavy rainfall events in the region, as well as more intense (though probably less frequent) tropical cyclones. There will be an increased threat to homes, businesses and roads in low-lying areas and along the Cairns coastline from river flooding and storm surge and cyclonic winds. In addition to flood risk, there is an increased potential for soil erosion and land slippage, especially on the steep slopes of the Kuranda, Macalister and Murray Prior Ranges. Local planning for development, stormwater drains, roads and bridges will be affected. We can expect more frequent interruptions to grid-based electricity supply as well as to fuel and other supplies due to shut down of rail lines, sea and air ports during extreme weather events. Working together to address back-up power and supply issues will help build Cairns’ resilience in the face of these changes.
Local planning for development and housing design will also be affected by projected changes in fire conditions. Fire weather is likely to increase in the Cairns landscape due to the combination of increased evaporation, higher average temperatures, and more frequent and hotter heatwaves. For example, evaporation is projected to increase on average by around 4% annually in north Queensland. Increases in some months are expected to be higher (e.g., 7% increase in January, projections from climate model Had GEM2-ES). Areas likely to be most impacted are those where the potential for intense bushfires is already high, for example among suburbs at the base of the ranges, as well as on the fringes of the northern beach settlements. Areas that are not currently considered to be at risk of severe bushfire (e.g. around Yarrabah) may become more vulnerable as fire weather increases and vegetation changes. Various programs are available to assist with developing and implementing adaptation strategies (for example, the QCoast2100 program for local governments to develop Coastal Hazard Adaptation Strategies http://www.qcoast2100.com.au/).
Natural systems have coped with changing climatic conditions in the past, but current changes are happening so fast that some species may not be able to adapt. Because climatic factors such as temperature and rainfall play such an important role in determining the suitability of different areas for plants and animals, we can expect that changes in temperature and rainfall will change the suitability of the landscape for certain species and systems. The result of climate change will be new combinations of plants and animals, sometimes in new locations, challenging our concept of what is ‘natural’. It’s also likely that this region will become more attractive to people moving from other areas that become less liveable. Increasing pressure for housing and more infrastructure to support growing populations will potentially lead a push for more clearing of native vegetation.
The Cairns landscape is likely to retain climate conditions that suit many of the species that are currently found here. However, some animals and plants may no longer be able to survive or reproduce in the area. For example, the northern leaf tail gecko is currently widespread and common in the area, but models show that by mid-century, climatic conditions throughout most of the region will be unsuitable for this species (http://climas.hpc.jcu.edu.au/maps/). Coastal species in particular are at risk from sea level rise, for example as beaches are inundated and freshwater wetlands and coastal scrub transition to salt-tolerant vegetation communities. There will be fewer nesting beaches for sea turtles, and a range of birds and mammals will be affected by the loss of freshwater wetlands. We can also expect widespread dieback of sea grasses and mangroves in lower intertidal zones, due to sea level rise, more intense cyclones and storm surges. These impacts will have a range of flow-on consequences for fish, dugong and other estuarine and marine life. Strategies such as the planned retreat of human settlements and infrastructure from coastal areas may reduce the risk to humans and also create opportunities for natural systems to shift landward.
In addition to the direct effects of increased temperatures and changed rainfall, climate change will have a range of indirect effects on other factors that drive natural systems. A major impact of climate change for natural systems will be more frequent and/or more intense disturbances, such as floods, fires, heatwaves and cyclones. For example,increased intensity and frequency of river flooding, together with increased water temperatures, will change aquatic systems, as well as those fringing waterways or on floodplains. More extreme rainfall events will increase the frequency of intense disturbance to in-stream invertebrates, animals and plants, and exacerbate the issue of soil and pollutant runoff entering the Great Barrier Reef lagoon.
Prospects are bleak for the Great Barrier Reef under a business as usual scenario of climate change. Bleaching of coral reefs will continue to be more widespread as average temperatures increase and heatwaves become hotter and more common. As hot spells occur more frequently, reefs won’t have time to recover from previous bleaching episodes and will eventually collapse. Reef systems will also be affected by more acidic sea water (caused by higher CO2), more intense cyclones and freshwater pulses associated with heavy rainfall events.
Managers of biodiversity are already working to minimise or reverse impacts of land clearing, pollution, introduced plants, animals and diseases on natural systems. Climate change is an additional impact that interacts with these existing pressures. The resilience of natural systems to cyclones and other disturbances is improved by having a large and well-managed network of protected areas. It’s not possible to predict the exact consequences of climate change for plants, animals and their habitats, but sharing observations, trying new management practices and monitoring their outcomes will help build the new knowledge required to promote adaptation of natural systems to climate change.