Climate Council report projects $855.1bn in Australian coastal flood losses by 2100

The report projects Queensland will have 93,157 properties at risk, followed by New South Wales with 71,210 and Western Australia with 51,366. The Gold Coast, Brisbane and Melbourne are expected to be the worst-affected metropolitan areas. The Gold Coast, described as the country’s most exposed urban area, faces $84.4bn in projected economic losses, while Melbourne’s losses are concentrated in low-lying areas around Port Phillip Bay and the Yarra River.

Peter Lake, a grazier in the Clarence Valley in the New South Wales northern rivers region, told the Guardian he knew he was “buying in flood country with … eyes open” when he moved there in 2007. His cattle farm, about halfway between Yamba and Grafton, borders the Coldstream River and has flooded five times since 2009. He said that on 130 acres, a major flood could leave only about 15 acres flood-free; in the historically big flood in 2022, “we only had just a few acres of flood-free land.” Drought and frequent floods meant he had not successfully grown a fodder crop for some years. “If we’re going to have more frequent and more severe major events … we need to change the way we think about how we manage,” he said. “If rising sea levels impact on us, it’ll just this make property less and less viable.”

The report is based on mapping coastal flooding by 2100, taking into account sea level rise and storm surges under the climate scenario known as RCP4.5, which projects a 2.7C increase in global temperature by the end of the century, similar to expected heating based on current policies worldwide. It was co-authored by Prof Tom Kompas at the University of Melbourne, whose modelling of the economic impacts was also published in the peer-reviewed journal Scientific Reports and drew upon localised projections at 239 hotspots around Australia.

Kompas said the costs—an estimated $274.3bn in property losses and $580.7bn in land use damages—were a conservative estimate and did not take into account the additional impacts of coastal erosion or significant ice sheet melt. He said the scale of agricultural losses, with damage projected to affect 619,713 hectares (1.5m acres) of farming land, meant there was potentially a food security issue coming as well.

Sea levels have risen on average by more than 22cm globally since 1900, with human-caused global heating the dominant cause of the rise since 1970. An additional 14cm rise is expected in Australia by 2050, increasing the frequency of permanent inundation and tidal flooding.

Kompas said reducing greenhouse gas emissions to limit global heating was of paramount importance, but “we have to start planning and responding and adapting now.” He said the work showed where the hotspots are and what assets will be impacted, so planning could begin. “The first thing, of course, is not to build on flood plains, which is common still,” he said.