$855 Billion and Nowhere to Claim: The Sea Is Coming for 267,000 Australian Homes

267,000. That is how many Australian coastal properties could be damaged or lost to rising seas and storm surge this century — more than a quarter of a million front doors, investment flats, weatherboard rentals and beach shacks. ⁷ The modelled bill is $855 billion by 2100, counted not in centimetres of sea-level rise but in houses unliveable and hectares unusable. ⁸ It is the first time Australia has priced its entire coastline at once, and the number lands less like a forecast than a mortgage statement arriving 75 years early.

What makes the figure hard to dismiss is that it is not built for shock. The work, published September 9 in Nature Scientific Reports and led by University of Melbourne researcher Tom Kompas with Tuong Nhu Che and the Australian National University's R. Quentin Grafton, covers 1,156 coastal sub-regions across six states and the Northern Territory. ^{2 7} This is the first national-scale assessment of its kind, rather than a patchwork of council-by-council flood maps. ⁸ Its power is in aggregation: every exposed estuary and surf suburb added together until the local problem becomes a national balance sheet.

The scenario behind the $855 billion is the middle path, not the worst case. It assumes global emissions peak around 2040 and warming settles near 2.7 degrees Celsius by 2100, with seas that have already risen about 22 centimetres since 1900 continuing upward. ⁴ That is a world the planet is currently on track to overshoot, which means the central estimate is conservative by design. ⁴ On those assumptions the loss splits into roughly $274.3 billion in direct property damage and about $580.7 billion in lost land use — the houses first, then the ground they stood on and what that ground could have earned. ⁴

Risk concentrates where Australians chose to live. Queensland carries the largest share of homes at risk, 93,157 properties, alongside about $214.5 billion in losses. ⁴ The Gold Coast alone is the single most exposed urban area in the country, with projected losses of roughly $84 billion, higher than any other city. ⁴ Western Australia carries the biggest state-level bill at about $230.5 billion. ^{8 9} Every coastal jurisdiction is exposed; there is no state where the shoreline is safe, only places where density turns water into money lost. ⁷

The sharper turn is not the size of the number but who is left holding it. Standard home-and-contents policies generally exclude the “actions of the sea” — coastal inundation, storm surge and erosion driven by the sea itself — so a block swallowed by a rising tide is not a claim, it is a loss. ^{13 17} Insurance bodies define those actions as coastal inundation, erosion and recession, with climate change driving rising levels and worsening each hazard. ¹³ As exposure to erosion, inundation and storm surge grows, the work warns, insurability is stretched to its limits and the mismatch between risk and protection widens. ^{16 17}

Canberra has looked at the gap without closing it. In March 2024 the federal Treasury published a consultation paper, Standardising natural hazard definitions and reviewing standard cover for insurance, inviting submissions on how coastal hazards are defined and what standard cover should require. ¹² The ACCC and the Financial Rights Legal Centre both filed submissions that April. ^{14 15} No standard-cover prescription in force answers the coastal owner's question: when the sea takes the land, who pays?

The Gold Coast just ran the live test. After Ex-Tropical Cyclone Alfred struck in March 2025, the city went to work rebuilding its beaches, with reporting attributing about $35 million in sand replenishment to the council effort. ¹ Verified figures place the full coastline-rehabilitation program — offshore dredging, back-passing, scraping and dune works — at roughly $37.2 million, with about $5 million more in emergency response and about $24 million budgeted by the council in a single financial year. ¹ Set that $35 million of fresh sand against the same city's modelled $84 billion exposure and the scale snaps into focus: a decade-scale stopgap, an example, not a solution. ⁴

The report presses for the two levers that change the trajectory: adaptation — managed retreat, coastal planning, building-code upgrades — and the emissions cuts that decide whether 2.7 degrees is a ceiling or a waypoint. ⁴ What it does not supply is a way to pay hundreds of billions that neither the insurance market nor current adaptation spending is sized to meet. ¹⁷ And the projections themselves assume a climate the world has not yet committed to staying under. ⁴ When the water takes the land, for now, the owner pays — and that is the unresolved question sitting at the bottom of $580 billion in lost land use. ¹³