Changing Weather – Southern Cassowary Coast

People on the Southern Cassowary Coast know that our ability to live in and manage the landscape is based on long experience of general seasonal patterns, but many will say that with a changing climate, knowledge based on past experience is becoming less reliable. The implications of this will be far-reaching, affecting our livelihoods and lifestyles, as well as our natural systems.  The science is telling us:

• Less predictable weather: Ongoing climate change will make it 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 protect native species.
• Climate change and industries: The industries of the Southern Cassowary Coast are all heavily dependent on climatic conditions. While a changing climate will present challenges to existing industries, there may also be new commercial and agricultural opportunities.
• Climate change and communities: Staying informed about potential impacts in our region, such as hotter weather and more intense weather events, will help communities to prepare and develop strategies to enable them to continue to thrive.
• Climate change and natural systems: In addition to rising temperatures and the implications this will have for plant growth and fruiting habits, natural systems will also be exposed to more intense disturbances as a result of climate change.  We will have to accept a ‘new natural’, with new combinations of plants and animals, sometimes in new locations.

There will be opportunities for everyone to get involved in shaping a resilient and sustainable future for the Southern Cassowary Coast.  For more information on climate change, including links to detailed climate change modelling for our region, go to the Climate Futures page.

Less predictable weather

Long-term temperature records from Cardwell show that, in contrast to temperature records for most other regions in the Wet Tropics, Cardwell’s average annual temperatures over the past 20 years have actually been below the long-term average much more often than they have been above it (Figure 1).

Long-term rainfall data from Cardwell shows 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 31.8°C to 33.3°C by 2030, 33.4°C by 2070 and 34.7°C by 2090 (Figure 3). Furthermore, there will be a longer season of high temperatures, with the average daily maximum temperature exceeding 30°C from September to May by 2090.

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.

Climate change and industries

Sugar cane and banana production will be directly affected by increasing average temperatures, evaporation, heat waves, extreme rainfall events and increasing atmospheric carbon dioxide. 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. Similarly, the growth and development of bananas is reduced by temperatures outside the optimum range of 25-30°C (Critical Temperature Thresholds Bananas), and north Queensland growers may lose their advantage if winters warm sufficiently in southern growing locations to enable an all-year growing season. Areas of cultivation in low-lying coastal areas will obviously also be vulnerable to sea level rise, and growers have bitter experience of the damage that can be caused by tropical cyclones. Climate change may also bring new pests and diseases, which we know potentially pose an enormous threat to our agricultural industries. The region’s grazing enterprises will also potentially be challenged by warmer temperatures, changed rainfall patterns, sea level rise and different pests and diseases.

Regional primary industries may also be impacted by increasing bottlenecks in processing or distribution networks. For example, heat waves, cyclones and floods all have the potential to result in shut down of industrial operations such as the Tully sugar mill, either through workplace health and safety concerns, power failure, inundation or damage. Operation of facilities such as the Cairns and Mourilyan sea ports will also be affected by storm surge, cyclones, flooding during heavy rainfall, and extreme heat. Considering the importance of ports 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 implications for the region.

Climate change will also impact the commercial fishing industry. People on the Southern Cassowary Coast have experience of 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 on the Southern Cassowary Coast is underpinned by the natural values of the area, including the coast and mainland forest areas. Climate-induced changes in the health and composition of natural systems, including the potential loss of iconic species (see below), will potentially have major impacts on tourism in the area. Since tourism is already very seasonal, prolonged hot weather and less predictable rainfall is likely to affect visitation patterns, while more extreme weather may influence tourists’ perception of their safety in the region. It is clear from our experience in places such as Mission Beach that successive strong cyclones can strongly affect tourism.

Changing climatic conditions will challenge our established ways of doing things, but may also present new agricultural and commercial opportunities. For example, it may be necessary to diversify or switch crops or breeds to suit new climatic conditions, or to change practices. In order to adapt to new and changing climatic conditions, we may need to shift farming and other commercial enterprises to different parts of the landscape. This could create opportunities for the restoration of wildlife habitat on former agricultural land, but could also create conflict between the need to protect existing habitat and also maintain production.

Climate change and communities

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 along the Southern Cassowary Coast 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 Tully is projected to increase from the current average of three to eight by 2030 (and to 12 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 0.65m by 2090 under a business as usual emissions scenario. By 2030, homes and other assets along the Southern Cassowary coastline would need to be 0.14 m higher (and by 0.79m 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 Tully and Murray 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 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 to the extensive low-lying areas along the Southern Cassowary coastline from river flooding and storm surge and cyclonic winds. People living in buildings that can’t withstand severe cyclones will be very vulnerable during cyclonic winds. 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 the region’s rail lines, sea and air ports during extreme weather events. Working together to address back-up power and supply issues will help build the Southern Cassowary Coast’s resilience in the face of these changes.

Climate change and natural systems

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’. Even fairly small changes, such as the increased recruitment of colonising (or pioneer) rainforest plant species can have a substantial effect on the suitability of an area for other plants and for some animals. 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 Southern Cassowary Coast 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, habitat for cassowaries will be impacted by sea level rise, with the loss of coastal freshwater wetlands, and by changes in the fruiting patterns of plants resulting from warmer temperatures and changed rainfall. These impacts will compound existing pressures on cassowaries, arising from habitat loss, predation and road kill. Modelling shows (http://climas.hpc.jcu.edu.au/maps/) that areas along the region’s coastline will rapidly become less suitable for cassowaries as temperatures increase over the next decade. Under a business as usual scenario of greenhouse gas emissions, suitable climatic conditions will continue to decline and will be lost from the coastal plain by the year 2085. In these models, suitable climate for cassowaries will contract to the foothills and ranges at higher altitudes in the west of the region. This modelling also shows substantial changes in climate suitability for the mahogany glider, meaning that areas we currently recognise as critical for mahogany gliders may become climatically unsuitable over the coming decades, and that suitable climate will be found in parts of the landscape the species doesn’t currently inhabit, including in areas that are currently cleared. In reality, changes may not unfold exactly as these models project, but these projections have complex implications for how we manage landscapes to protect our plants and animals; we have to protect areas that are currently important so that threatened species survive, but also consider where important habitat will likely be in the future, together with whether and how plants and animals would be able to move there and establish. These considerations affect our decisions about which areas to protect and restore, as well as how to manage factors such as fire in these areas.

Coastal species are at particular risk from climate change and rising sea levels. For example:

• Critically endangered littoral rainforest systems are under extreme threat from climate change, as beaches are inundated and freshwater wetlands and coastal scrub transition to salt-tolerant vegetation communities. These natural systems protect a diversity of threatened plants and animals, as well as protecting coastal settlements.
• There will be fewer nesting beaches for sea turtles.
• A range of birds and mammals will be affected by the loss of freshwater wetlands as beaches and dune systems are inundated or eroded.
• Freshwater wetlands and coastal floodplains, together with the abundant wildlife they support, are under threat from more intense flooding during heavy rainfall events and salt water contamination due to sea level rise and storm surge.
• We can expect widespread dieback of sea grasses and mangroves in lower intertidal zones, due to sea level rise, more intense cyclones and storm surges, affecting 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, 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. Narrow riparian vegetation will be particularly vulnerable. More extreme rainfall events will also 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. On a national scale, the Tully and Murray Rivers are among a small number of watercourses identified as being priorities for conservation of freshwater biodiversity under climate change.

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. 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.