A new report from a climate change advocacy group estimates the costs of protecting public infrastructure from rising seas. And the Florida Keys are facing one of the biggest bills.
The Center for Climate Integrity estimates it would cost more than $400 billion to build seawalls that would prevent frequent flooding in the near future of the nation's roads, schools and hospitals.
The cost in Monroe County alone is estimated at more than $11 billion. That's the most by far of any county in Florida and the second highest county cost in the country.
But while the Keys are preparing for climate change, they're not planning to build seawalls around the islands.
It would be too expensive – and it wouldn't work anyway, according to Rhonda Haag, Monroe County sustainability director.
She says with the porous ground in the Keys, water doesn't just come from the ocean.
"Areas that are low-lying roads, water comes in, even if it's not a shoreline road, it comes in from in from underneath in the low-lying areas, so that's already occurring," she said. "So seawalls are not the answer."
Monroe County already has a pilot project underway to raise two roads that frequently flood. Initial estimates are that the projects cost between $2 and $10 million a mile, depending on how much they need to be elevated and the cost of stormwater treatment.
Haag said the county is also making sure that new county buildings, like a fire station on Stock Island, are built to stay dry after 50 years of projected sea level rise.
"The answer to Monroe County for long term livability here is going to be learning to live with water," she said. "We're definitely doing the investment here to make sure our residents can live here for the future, at least for the next few decades. Now longterm, 100 years or more, that's a different story. It all depends on how high the seas rise."
The report's authors say they don't expect every coastline to build seawalls but that it provided a consistent baseline for a national estimate.
"We needed a consistent measure that we could apply across the country," said Richard Wiles, executive director of the Center for Climate Integrity. Some areas "may not use seawalls per se, but they'll have to do something."
Other measures to protect and adapt may be even more expensive, he said.
The report's aim is to illustrate the costs of climate change that local communities are facing — and advocate for holding the fossil fuel industry responsible for those costs.
"Taxpayers are on the hook for all the costs," Wiles said. "Polluters are paying nothing."