The coastal zone of Australia played a significant role in the life and livelihoods of Indigenous people before colonisation in the 1700-1800s. It is well established that Aboriginal people have lived on this continent for 50,000 to 60,000 years.

In testament to the significant nature of their culture of orals traditions, stories have been traced back in 21 locations that show knowledge of coastal inundation that appears to recall the effects of postglacial sea-level rise more than 7000 years ago.

The early location of many early colonial settlements, and the urban settlements that followed, was based on a temperate climate. For many locations this meant regular rainfall, access to fresh water (and assumptions of a stable climate). In contemporary Australia, this has produced a settlement pattern of around 87% of the population living within 50 km of the coast.

Climate change is now affecting the viability of these settlements: planning and action is required to ensure they are adapted to a different set of future climate conditions.

Most coastal cities and towns are undertaking this type of climate change planning response. An understanding of the climate, and its variability including weather extremes, is now incorporated in many plans and regulations that affect coastal communities.

The subsequent implementation and action is more difficult and takes time, resources and effective leadership.

Climate influences the design and location of settlements and buildings in a range of ways.

• Location and growth of settlements on coastal floodplains is increasingly considering understanding of river flood frequency and extent. This understanding is now being challenged as many coastal cities experience large flood events more regularly.
• Coastal setbacks (buffer zones that have no permanent constructions) in planning guidelines are informed by knowledge of erosion risks from cyclones and storms
• Knowledge of tides and significant wave heights underpins the design and construction of coastal protection works, harbour works and jetties.
• The Building Code of Australia requires that buildings withstand likely physical impacts, including those from gale-force winds during tropical cyclones and East Coast Lows. To this end they have developed a climate zone map to inform building design and construction practices.

In considering change to human settlements, it is important to also consider climate justice

Climate justice is crucial for the wellbeing of Australia's coastal communities, especially in regions where rising sea levels, coastal erosion, and extreme weather events threaten homes, cultural heritage, and livelihoods. Many of the most vulnerable communities, often contributing least to global emissions, face the most severe impacts of climate change.

Understanding average and extreme climate is critical to help protect household assets and community safety. The following are examples.

• Insurance companies use models based on the frequency and severity of historic extreme weather events to determine the coverage and cost of insurance for coastal properties.
• The elevation of evacuation routes in coastal floodplains, and thus community safety during flood events, is determined by the height of previous floods in the area.
• Some communities in areas prone to extreme events are recognizing they need to be better prepared through adaptation, resilience, and disaster planning by forming information or formal resilience groups.

The coast plays a vital role in supporting physical and mental health, offering unique environments that enhance wellbeing through recreation, nature connection, and cultural practices. Blue spaces, including beaches and waterways, are associated with increased physical activity, social interaction and reduced anxiety and depression.

The coast also holds deep cultural and spiritual significance for Aboriginal and Torres Strait Islander peoples. Connecting with Sea Country is linked to improved mental wellbeing and a stronger sense of belonging.

Sea Country refers to the deep cultural, spiritual, and ancestral connections that Aboriginal and Torres Strait Islander peoples have with the ocean and coast. It includes the sea, marine life, reefs, tides: these elements are alive and connected to ancestors, stories, and spiritual beliefs.

Part of a broader worldview, caring for Sea Country acknowledges that people belong to and care for the sea through respect, responsibility, and reciprocity. Like caring for Country, caring for Sea Country is a cultural obligation that is carried out through song, ceremony, storytelling, and everyday practices passed down through generations.

Recognising Sea Country means valuing Indigenous knowledge and reshaping how decisions about the ocean are made, based on care, connection and shared responsibility. It also also linked with acknowledgement of Indigenous fishing rights and support for other economic opportunities for Indigenous mob.

Australia’s coastal ecosystems are adapted to the atmospheric and marine climates they experience and so any changes in climate will lead to changes in these ecosystems. Land-based ecosystems are influenced by patterns of air temperature and precipitation, which include daily and seasonal changes along with humidity and wind, and the nature of the land surface. At the shoreline, important drivers are wave energy, tidal range and water temperature.

For many coastal ecosystems, their distribution and health are mainly determined by temperature. For example, many reef-building corals have evolved within a narrow range of preferred temperature and few species survive quite small increases in temperature – even just 1-2°C hotter – if the warmer conditions persist for too many days. There have been several coral bleaching events on the Great Barrier Reef over the past two decades, with four mass bleaching events between 2016-2022.

Small changes in temperatures are being shown to affect some coastal species and even coastal ecosystems, which have important implications for coastal settlements that depend on the ecosystem services they provide.

• Recurrent coral bleaching in the Great Barrier Reef has been widely reported over a series of recent summers. Depletion of this internationally significant ecosystem includes the loss of biodiversity, the loss of the coastal protection offered by the reef system, and the decline of the valuable tourism industry that sustains many coastal communities.

• Turtle embryo development also occurs within a narrow thermal range with the sex of a turtle determined by the embryo’s incubation temperature. A decline in turtle breeding capacity is likely to reduce the population, with cultural impacts for Indigenous people through cultural knowledge and ceremonies connected to these species.

• Recent declines of giant kelp off the eastern and southern coasts of Australia have been attributed to rising sea temperatures. Demise of kelp forests includes a decline in this natural carbon sequestration capacity, plus a loss essential habitats for shelter, breeding, and food sources of many other marine species include those important for commercial fisheries

There are no up-to-date estimates of the impacts of climate change on the Australian coast. However, there are several reports that help to create a picture of the significant costs.

Now more than 15 years old, the 2009 Climate change risks to Australia's coasts: a first pass national assessment, which suggests a $63 billion the estimated replacement value “of existing residential buildings that are potentially at risk of inundation from a 1.1 m sea-level rise, with a lower and upper estimate of risk identified for between 157,000 and 247,600 individual buildings.”

Given its age, these figures are considered an underestimate because there has since been much more development in the coast. Also, replacement costs would be significantly more because of the increase in materials and labour. A supplementary report in 2011 reported on commercial and light industrial buildings and transport infrastructure.

A 2022 report of the Economic impacts from sea level rise and storm surge in Victoria, Australia over the 21st century (full report and summary) considered the impacts across residential and commercial assets, reserves and conservation areas, infrastructure, parks, industrial and agricultural assets.

• Losses are estimated to be more than $337 billion in 2100, or 2.68% of the projected gross state product (GSP) of Victoria.
• Economic damages (market and non-market values) varied considerably across the different subregions and land use classes of Victoria. Economic losses in residential areas will be mostly around Port Phillip Bay and areas east of Melbourne. Most commercial damage will be around Docklands and Southbank.
• The (separately modelled) impacts from sea level rise and storm surge on wetlands potentially add between $46.05 billion and $104.92 billion to the 2100 loss estimates.

For infrastructure that supports economic activities, climate plays a critical role in shaping its design, location, and operation. Today, climate thresholds and operating ranges are incorporated into the design, construction, and management of both small and large-scale infrastructure. The importance of this integration is revealed when these climate thresholds are exceeded.

For example, the 2009 heatwave in southeast Australia, thousands of Victorian businesses and households lost power when the Basslink interconnector (which allows trading of electricity between Tasmania and the mainland) shut down after it reached maximum operating temperature.

For coastal industries that depend on natural resources such as fisheries, productivity is linked to oceanic climate factors, particularly sea surface temperatures and seasonal patterns in coastal currents. Impacts of changes to marine life will be experienced across scales: from individuals to communities and organisations.

Coastal ecosystems (both terrestrial and marine) are one of the major drivers of Australia’s tourism industry, supporting important and iconic locations for recreation and sport. The Great Barrier Reef catchment receives about 2.3 million international and 1.8 million domestic visitors per year (Tourism Research Australia 2015). It contributes $6.4 billion annually to the nation's economy and supports 64,000 jobs. (Deloitte Access Economics 2016).