Understanding the risks
Most Australian capital cities are located within the coastal zone. It is a conduit for Australia's exports and imports and much of the nation’s commercial activities occur in coastal areas. Large numbers of Australians enjoy the recreational benefits the coast provides and the uniqueness of coastal environments such as the Great Barrier Reef.
Climate change impacts in the coastal zone
The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report in 2007 estimated global sea level rise of up to 79 centimetres by 2100, noting the risk that the contribution of ice sheets to sea level rise could be higher than predicted and lead to greater rises in sea level. Recent findings suggest the climate is changing faster than projected. Under a high-emissions scenario, a sea level rise of up to one metre or more by the end of the century is plausible. Regardless of reductions in greenhouse gas emissions, sea level will continue to rise for centuries, with an eventual rise of several metres possible. This has implications for decisions taken now on the ‘footprint’ of Australian cities.
Rising sea levels are likely to cause accelerated erosion of many beaches around the Australian coastline. The switch from generally accreting beaches to a receding coastline is a key threshold for coastal management and is not well understood.
The risks of sea level rise are not confined to the coast itself. Flooding may impact on areas some distance inland, for example along estuaries, rivers, lakes or lagoons.
Changes in the frequency and magnitude of extreme sea level events such as storm surges combined with higher mean sea level, will lead to escalating risks of coastal inundation. With 50cm of sea level rise, inundation events that previously occurred once every 100 years could happen several times a year. Some studies suggest that there will be an increase in the intensity of cyclones, and that they could track further south along Australia’s east and west coasts; although the total frequency of cyclones may possibly decrease.
There is time to prepare coastal areas for a changing climate if it is started now.
Maps of sea level rise
Many of the risks from climate change can be managed if preparation starts now. Communities and decision-makers need early access to information and data to help understand the potential impacts and manage the risks.
The Department has developed a series of maps that illustrate the potential impacts from three sea level rise scenarios (low, medium and high). The maps highlight low-lying areas that are more vulnerable to inundation from sea level rise combined with a very high tide; an event that could be expected to occur at least once a year. They provide additional information for coastal communities to consider.
Coastal climate change case studies
A number of case studies are being finalised that provide a local scale examination of a range of coastal climate change issues, including in the Pimpama catchment in the Gold Coast region, the Hunter region, and the South Australian Yorke Peninsula.
A recent study titled Kakadu: Vulnerability to climate change impacts looks at the impacts of rising sea levels as a result of climate change that are likely to result in increased saltwater intrusion, with associated risks to fresh water ecosystems, areas of cultural significance, and tourism in Kakadu National Park.
The east coast Tasmanian rock lobster fishery—vulnerability to climate change impacts and adaption response options study examines the potential impacts of climate change on the Tasmanian rock lobster fishery, and identifies several options and opportunities for adaptation.
The Department has also released a report that analyses the benefits and costs of adaptation in response to risks of flood inundation from Narrabeen Lagoon in Sydney’s northern beaches area.