Miami could be the American Atlantis

Picture perfect - but rising seas pose a grim threat to South Florida. Photo / Florida Times-Union

If nothing else climate change is a boon to dystopians. Last year Rolling Stone published an arresting vision of life in South Florida - mostly mosquito plagued swamp a century ago - in 2030, as a hurricane storm surge drowns hundreds, trashes fabled seaside hotels, destroys beaches, rips up roads, corrodes electrical wiring and inundates water and sewer pipes to leave America's tropical playground "wet, vulnerable and bankrupt". Miami becomes an "American Atlantis," the victim of man's delusion that nature can be defied.

Could it happen? Many scientists believe that, without radical mitigation, the process is already under way, maybe at the point of no return. Built on porous limestone between the Atlantic Ocean and the Florida Everglades, Miami - home to some 5.5 million people - has the unenviable distinction of being on the front line of climate change, where rising seas and storm surges are a major challenge.

Take South Beach, famous for white sand beaches, art deco buildings and hedonistic lifestyles. A low-lying barrier island between the Atlantic and the corporate towers of downtown Miami across Biscayne Bay, South Beach is prey to sea surges, pumped up by hurricanes or full moon tides, that swamp streets, back up storm drains and trickle into the ground floors of stellar-priced homes.

"Clean sky flooding, which involves tides but no rain, is increasingly common," says Professor Ben Kirtman, an atmospheric expert at Miami University. "Add on an autumn thunderstorm or a hurricane surge and it gets much worse." Hundreds of millions are being spent to upgrade sewers and drains, with US$1.5 billion earmarked for such work. Huge pumps, used in New Orleans to evict seawater after Hurricane Katrina in 2005, are planned. Yet, even if seawalls are built, seawater can flow inland via porous limestone and seep into foundations.

Some think the only solution, short of abandonment, is to raise the entire city. "It's daunting," says Kirtman, "but historically it's happened in other cities."

"Change is incremental, with roads raised during maintenance. If over half of a building needs renovation city codes designate it as a tear-down. Foundations are enclosed, a "bath tub"effect that keeps water out.

On a larger scale Miami Beach might be encased in a "sea curtain "designed to keep water out, a massive undertaking involving pumps and a wall anchored on the sea floor below Biscayne Bay.

But abandonment is a possibility. The 2014 UN Intergovernmental Panel on Climate Change forecasts a global sea level rise of 0.3 to 1.2 metres by 2100, regarded by many as a conservative estimate. Studies of projected sea rise show a sharply climbing curve as climate warms up.

Much of South Florida sits below 1.8m. A 0.9m rise would swamp about one-third of the land area. A 1.8m rise about half. Even a 0.3m rise would pollute fresh water supplies with salt water.

Miami is not alone. A 2013 study in Nature says rising seas, sinking land and coastal development could cost US$1 trillion in annual damage by 2050 unless action is taken. The 10 most at-risk cities, plus the flood bill, include three in the US: Miami [US$2.5 billion], New Orleans [US$1.8 billion] and New York [US$2 billion].

"Sea level rise is a very inert mechanism," co-author Stephane Hallegatt, a World Bank economist, said. "Once it gets started it can last for centuries." Dykes and seawalls may fail.

But action is cheaper than inaction and the study estimates a US$2 billion per city cost for new infrastructure - such as pumps or river barriers - plus maintenance.

The study postulates it will then cost US$50 billion a year to protect 136 coastal cities with over one million inhabitants.

Absent mitigation insurers may jack up rates or deny coverage, devastating local economies. The likely result would be plunging property values, an exodus of people and investors and a flat-lined tax base. It is a recipe for urban disaster.

The Organisation for Economic Co-operation and Development cites Miami as the US city most vulnerable to climate change, with over US$416 billion in assets at risk.

Canals dug last century to drain swamps for developers now conduct seawater inland, even as ever more water is taken from the Biscayne aquifer to supply business and homes, reducing the pressure head that keeps seawater out.

Bizarrely, boosters continue to beat up Miami's potential. The city is on a roll, sprouting condos, hotels and commercial structures as property prices surge and people flock to the bonanza.

Local officials may be worried but business seems indifferent to the threat, maybe assuming a technological fix will save the day. It is an attitude fostered by the state's Republican establishment, where climate change denial remains the norm.

Governor Rick Scott, who supports off-shore oil drilling, told the Tampa Bay Times he has "not been convinced" global warming exists. Senator Mario Rubio told ABC News he does not believe "human activity is causing the dramatic changes to our climate the way these scientists are portraying it".

He contends climate change mitigation will torpedo the economy. His beliefs are common among rich conservatives.

A study by Climatic Change this month found that as wealth increases there is an increased likelihood of Republicans "dismissing the dangers associated with climate change". Poorer Republicans, plus Democrats or Independents, are less likely to be deniers.

Texas, the largest contributor to greenhouse gas emissions in the US, is also menaced by rising seas along the Gulf of Mexico littoral.

This is especially troubling for Galveston, built on a barrier island where a 1900 hurricane killed some 8000 people.

Sea level is rising. says John Anderson, professor of oceanography at Houston's Rice University, by 2.5mm to 3.00mm a year. Barrier islands are in retreat.

"The erosion of our barriers is removing the first line of defence to storms and seriously threatens inland cities like Houston," he says. But "most policy makers in Texas," including Governor Rick Perry, remain in denial.

While local officials fret denial at the top is a major handicap to asking taxpayers to pay for costly mitigation their elected leaders suggest is not really necessary.

Which begs the question: are low lying cities like Miami or Galveston viable? It is a hard question to answer. Inhabitants face a stark choice: build costly defences - Holland will spend up to 1 billion a year this century to strengthen 3700km of dykes and dams - or abandon the area.

The other option is to reduce the greenhouse gases driving climate change. But there is scant political will for that.

Ultimately, no US city or state will be able to foot huge mitigation bills alone. They need federal aid. Partisan politics, climate change denial and cost are stumbling blocks to any Dutch-like national scheme. It's the American way.

Meanwhile, South Beach awaits the next inundation, the canary in the climate change mine.

Will Miami be the first US city to succumb to climate change? "Miami, as we know it today, is doomed," Harold Wanless, chairman of the geological sciences department at Miami University, told Rolling Stone.

"It's not a question of if. It's a question of when." As the unthinkable - a modern US city faced by climate catastrophe - looms ever closer it will take a lot more than Canute-like posturing by politicians to rescue Miami from the waves.