Climate change threatens Australia's coastal lifestyle with over $850 billion in projected damages

Climate change means Australia's love of the coast is facing a multi-billion-dollar reckoning, new research suggests, as rising seas threaten to turn its prized coastal lifestyle into a question of who will foot the bill: property owners or governments.

In the first nationwide assessment of economic losses due to sea level rise, researchers from the University of Melbourne, the Australian National University and Global Environmental and Economic Modelling have found all coastal states and the Northern Territory face hefty damage bills this century.

Australia could face damage costs of more than $850 billion, with more than $274 billion going towards property losses and $580 billion spent on land use damage.

Co-author Tom Kompas said the findings were "alarming", and the economic toll would mount as fossil fuel emissions continued to drive global temperatures higher.

"We keep warming the planet … so you get more sea level rise, you get higher tides, higher king tides, higher maximum tides," the professor of environmental economics and biosecurity at the University of Melbourne said.

"You get more intense and maybe even more frequent storms and storm surges and that causes localised flooding."

Sea level rise hits hard across the board

As temperatures rise, melting ice and the thermal expansion of warmer seawater cause sea levels to rise, threatening coastal communities worldwide.

The Australian research found more than 267,000 coastal properties and 2 million hectares of land across the country will face flood damage by 2100 based on global carbon emissions peaking around 2040 and global warming being limited to about 2.7C.

The United Nations has warned that warming will hit at least 1.8C above pre-industrial levels and is projecting that figure could reach up to 2.6C by the end of the century under current policies.

The findings also put a price tag of more than a trillion dollars on impacts associated with global warming exceeding 4C — however, that level of warming was predicated on growing fossil fuel use and scientists have deemed it unlikely to eventuate due to the uptake of clean energy.

Queensland has been identified as having 93,000 properties at risk of damage due to sea level rise, resulting in an expected damage bill of $214 billion for the state.

The Gold Coast is the single most exposed urban area in Australia, with projected economic losses at $84.4 billion.

Western Australia faces the largest total losses, while in New South Wales, communities in the state's north and Central Coast region face higher property losses than in Greater Sydney.

With Victoria the only jurisdiction where property damage costs exceed those associated with land use, Professor Kompas said the research underscored the significant costs of inundating farmland and recreational areas.

"Much of it is badly, badly damaged with sea level rise and storm surge … damaged reserves, parks, beaches," he said.

"So it's not just individual properties, commercial and residential properties; it's a wide range of assets that are being impacted."

Consequences with every centimetre

The economic assessment forms the basis of a report from the Climate Council, which highlights how coastal floods that were previously considered severe will become a regular occurrence in the future.

It found that every 10cm of sea level rise will triple the frequency of "once-in-a-century" flood events.

Global sea levels have already risen by over 22cm since 1900, with projections there could be an additional 14cm by 2050.

Report author and Climate Councillor Andrew Watkins said the impacts were already being felt.

"We have seen quite a rapid increase in what we call extreme water levels along the coast, and that gives coastal inundation, coastal flooding and coastal erosion as well," the Adjunct Professor at Monash University's School of Earth, Atmosphere and Environment said.

Sea level rise can damage coastal land and infrastructure in multiple ways; one being permanent inundation. Scientists often use the "1 to 100 rule" to describe this — meaning seawater will go about a metre inland for each centimetre of sea level rise.

So 10cm of sea level rise can actually move water 10 metres further inland, inundating any land or building in its path.

Rising seas can also contribute to isolated coastal flooding events when combined with storms.

"When you have that sea level rise, and then you get a storm surge where the storm is pushing the water up against the coast, it makes the water go even higher," Dr Watkins said.

"Then you get waves on top of that, and if it happens at high tide, that's when you get the full combination of impacts."

Storm surges and wind-driven waves linked to Ex-Tropical Cyclone Alfred led to severe erosion along the coastline between south-east Queensland and north-east NSW last year, with the Insurance Council of Australia announcing more than 125,000 claims totalling $1.36 billion.

Associate Professor of Climate Adaptation at Griffith University Johanna Nalau said recovery from that event was still ongoing.

"There has been a lot of work on beach nourishment and then more acute damage, so we talk about power, power networks, transport, water and sewage; those were resolved within weeks to months," she said.

"But the coastal erosion part is still an ongoing effort, and there has been some reporting in the news as well that some of the housing damage that people experience hasn't been resolved yet."

Bracing for the future

Experts are calling for improved efforts to help coastal regions adapt as climate change not only contributes to rising sea levels but is also expected to increase the frequency and intensity of storms.

Warnings of a mounting economic toll have also raised questions around who will foot the damage bills going forward, particularly given insurance generally does not cover "actions of the sea".

"Most coastal properties would have some level of insurance, although the insurance sector is also very, very aware of risks that come with climate change," Dr Nalau said.

Dr Watkins said it was becoming "prohibitively expensive" for some councils to pay for adaptation and recovery.

"A lot of councils are effectively having to dip into their own coffers to support resilience building, but also to recover from damage that's done when we have these storm events and sea level events along our coastlines," he said.

"We do need to look at this as a national problem and develop plans with the communities and with the local, state, and federal level about the best ways to go forward."