Past the towers of downtown Miami and over Biscayne Bay sits the city of Miami Beach. Perched on the tip of a narrow barrier island, Miami Beach is a resort community of just under 100,000 people, though its population swells with a steady stream of tourists. Through the wall of hotels that line its shore is the city's central draw: the wide, white stretch of Miami Beach's beach.

The beach is the centerpiece of the city’s promise of escape — escape from cold winters or college classes or family, where you can drink goblets of bright green liquor and cruise down Ocean Drive in a rented tangerine Lamborghini before retiring to the warm sand. To the casual observer, the beach may look like the only natural bit of the city, a fringe of shore reaching out from under the glass and pastel skyline. But this would be false: the beach is every bit as artificial as the towers and turquoise pools. For years the sea has been eating away at the shore, and the city has spent millions of dollars pumping up sand from the seafloor to replace it, only to have it wash away again. Every handful of sand on Miami Beach was placed there by someone.

That sand is washing away ever faster. The sea around Miami is rising a third of an inch a year, and it’s accelerating. The region is far from alone in its predicament, or in its response to an eroding coast: it’s becoming hard to find a populated beach in the United States that doesn’t require regular infusions of sand, says Rob Young, director of the Program for the Study of Developed Shorelines at Western Carolina University. Virginia Beach, North Carolina’s Outer Banks, New York’s Long Island, New Jersey’s Cape May, and countless other coastal cities are trapped in the same cycle, a cycle whose pace will become harder to maintain as the ocean rises.

"There isn’t a natural grain of sand on the beach in Northern New Jersey; there is no Miami Beach unless we build it," Young says. "The real endangered species on the coast of the US isn’t the piping plover or the loggerhead sea turtle. It’s an unengineered beach."

The sea has been slowly cutting a divot into the shore in front of Miami Beach’s iconic Fontainebleau hotel, encroaching nearly to the promenade. Patching it would normally be a small job. But Miami Beach has a problem, one more cities will soon face: it has run out of sand in the ocean nearby.

The beach is the tattered edge of the land. It’s made of debris, which we call sand when it’s too small to think about discretely, though exactly what it consists of varies. It could be pulverized coral, like in the Maldives, or crushed clamshells, like Shark Bay, Australia, or discarded glass, like around Fort Bragg, California. Often it’s rock that has been crushed by glaciers or eroded off mountains and washed down rivers to the sea. Beaches made from black basalt or purple garnet have a certain novelty value, but the ideal beach, the one you see on ads for airlines and beer, is sugary and white. It’s likely calcium carbonate or quartz.

Coastal engineers talk about "beach behavior," as if dealing with an unruly animal rather than a geologic feature. Waves sort sand grains to a depth where they no longer move them, so some beaches change with the seasons, as winter storms suck sand offshore, leaving only cobblestones, and smaller waves push it back in the summer. One thing all beaches have in common is that they’re always shifting, wave by wave over years or overnight, with a storm.

For much of the 20th century, people tried to hold beaches in place by building groins — lines of rock or wood pylons protruding from the shore. But groins robbed downdrift beaches of sand that would have come their way, creating new erosion problems. (Some came to be called "spite groins.") Seawalls made things worse, further blocking the natural movement of sand and forcing waves back onto the shore, scouring away the beach. By the 1970s, there was very little beach left on Miami Beach or shore at the Jersey Shore. So a new response became popular: add sand.

That job largely fell to the US Army Corps of Engineers. Dredges floated offshore, extending scoops or hoses tipped with cutter heads into the seafloor and piping sand back onto the eroding beach. Nourishment, as the practice is called, maintained the beach, but it was also an admission that there would never be a permanent solution to fixing the shore in place. Once you start nourishing a beach, you can never stop. Its equilibrium state lies elsewhere, and wave after wave will eat away at the shore, and you’ll keep having to find new sand to replace it.

Sand seems like an infinite resource, but it isn’t. You can’t put just any kind of sand on a beach. Forget about the thousands of miles of dunes in the Sahara and Gobi — rounded by wind, those grains are too smooth. Sand made by crushing rock is too jagged. Stones worn down by rivers and waves over millennia is ideal, but even then, it has to be the right type. If the grains are too small, they wash away quickly; too large, and the beach becomes a steep bank. If they’re the wrong density or wrong shape — say, plate-like shards of broken shells — they’ll float in the water, causing clouds. If the sand is too dark it will trap heat, and can shift the gender of sea turtles born there. "You want to match the native sand as close as you can," says Kevin Bodge, a coastal engineering consultant. "That sand was there for a reason."

Once you start nourishing a beach, you can never stop

Tremendous amounts of ocean sand gets used for land reclamation and construction. Countries use it to extend their borders, like Singapore and China, which has built seven new islands in the South China Sea. Billions of tons of sand gets poured into concrete. A United Nations report on sand shortages found that up to 60 billion tons of sand and gravel are mined each year, more than twice the amount moved by all the rivers in the world, which the report notes makes "humankind the largest of the planet’s transforming agents with respect to aggregates."

The United States has lined its coasts with over a billion cubic yards of sand, at a cost of $8.6 billion, according to a database maintained by Andy Coburn at Western Carolina University’s Program for the Study of Developed Shorelines. All that sand inevitably washes back into the sea. Sometimes waves bring it back, but for the most part, it’s lost to us; if it’s sucked out past a certain depth, it’s scattered along the continental shelf, too dispersed to be gathered back.

With sea levels rising, demand for beach sand is only going to grow. About 57 percent of the coast in the lower 48 states is already eroding, according to the USGS. "Every single coastal erosion problem we have right now is only going to get worse, not better," Young says. "It’s only going to erode faster, not slower, require more sand, not less." Gradually now, but soon overwhelmingly, every coastline is going to want to move inland. Young foresees a future of rising costs and conflict over diminishing sand. "If you want to invest, buy a dredge."

No state requires more sand than Florida, which sits in the middle of hurricane alley and has the longest coastline after Alaska. Half of the 825 miles of beaches monitored by the state’s Department of Environmental Protection are designated as critically eroding, from Daytona Beach to the Kennedy Space Center on Cape Canaveral to the shore in front of Mar-a-Lago, the Palm Beach estate of President Donald Trump.

On July 31st, 2015, the Army Corps released a plan for patching eroding sections of Miami Beach. Miami-Dade’s sand resources had been exhausted, the Corps wrote, and some of the best alternatives lay to the north, offshore of Martin and St. Lucie counties. Though the shoals were in federal waters and the northern counties had no greater right to them than anyone else, they viewed the sand as theirs, and with the Corps’ announcement began the latest skirmish in what local officials call "the sand wars."

State Senator Joe Negron, whose district includes parts of Martin and St. Lucie, swore that Miami-Dade "wouldn’t get a single grain." Frannie Hutchinson, a St. Lucie commissioner, demanded the Corps "take its shovels and buckets and go home." She filed 15 public comments on the Corps’ proposal, saying that it failed to address sea level rise and would rob St. Lucie of needed sand. The county erosion chair for 14 years, Hutchinson says that she cringes every time she sweeps dirt out of her house. "Do you know how much sand is in there? You can’t replace sand."

There was a sense, in council meetings and public statements, that Miami Beach was reaping what it sowed, and that with the sea rising, it was every county for itself. "They’ve squandered their sand, they’ve overdeveloped, they’ve depleted their resources and now they want to come and take ours," says Sarah Heard, a Martin County Commissioner. "We need to protect that offshore site, we need to guard it very carefully. We don’t know exactly how sea level rise is going to impact us, but we know it’s accelerating rapidly, we know there’s going to be inundation."

"They’ve squandered their sand."

Heard is a Republican, but laments her party’s denial of climate change. (Last year, the Florida Center for Investigative Reporting found that the state's governor, Rick Scott, forbid state officials from using the term in emails or reports.) Jacqui Thurlow-Lippisch, another Martin County commissioner who objected to the Corps plan, is also a Republican, and also clear-eyed about what rising seas will do to her community. Just as there are proverbially no atheists in foxholes, it’s increasingly difficult to be a local politician in coastal Florida and deny the sea is rising.

Yet what to do about it at a local level is a conundrum. Right now, the answer is to keep piling on more sand. Thurlow-Lippisch describes nourishment as a loop her town is trapped in: the most expensive property is on the beach, she says, and letting it fall into the sea would rob her county of 30 percent of its tax base, making it impossible to fund schools, run buses, and provide lunches for children in need. Though she wonders whether she’s doing the right thing, she continues to fight for the sand that her community will eventually have to put on its shore. "We all have to look ourselves in the mirror and ask, is this a sustainable life? What are we doing here? But right now, we’re in it, we’re doing it."

As the northern counties lobbed angry missives at the Corps, one alternative kept coming up: the Bahamas.

The nearest Bahamian islands are just 50 miles east of Miami. The sand grains there aren’t rock, but orbs of calcium carbonate called aragonite, which some scientists believe is formed by bacteria as deep ocean water moves into the warm, shallow banks of the Caribbean. The exact process that produces the sand is poorly understood, says Lisa Robbins, an oceanographer who studies it, and occurs in only a few other places in the world, such as the Arabian Gulf.

One thing is clear: it’s premium stuff. "They’re not only mysterious, they’re gorgeous, and wonderful to step on," Robbins says of the grains, which she likens to "little pearls." The sand is so white that when coastal engineer Kevin Bodge brought in a barge’s worth in the early ‘90s for Fisher Island, a wealthy community willing to pay for it, the customs official looked on incredulously.

"It was 1991," Bodge recalls, "the height of the Miami Vice thing, so we had to clear customs, and it came in on a barge and when the sun hit that thing coming over the horizon in the early morning light, it was the most incredible pile of gleaming white powder I’ve ever seen. The customs agent just looked at me and said, ‘You gotta be kidding me.’"

The Bahamian government had been ambivalent about selling sand to nourish foreign beaches, says Anthony Myers, whose company holds a lease on a shoal near Bimini — why let tourists visit Bahamian sand beaches elsewhere? But in 2010, it relented. "I’ve helped them understand the science," Myers says. "If you don’t sell this, you’re just watching your money disappear into the chasms of the ocean."

"It was the most incredible pile of gleaming white powder I’ve ever seen."

Myers sells sand for plastics, agriculture, and other purposes, but to his great frustration, he has been unable to get his sand on Florida’s beaches. The federal government often pays half the cost of beach nourishment, with states and cities splitting the rest. But an amendment to the 1986 Water Resources Development Act prohibits federal funds from going toward foreign sand if domestic sources are available, which means anyone who wants Bahamian aragonite would have to pay the tab themselves.

His consultant on the mainland, Jayson Meyers (no relation), shares his frustration. Sitting in a concrete and glass tower in downtown Miami, Meyers pulled out a plastic vial of Bahamian sand from his leather briefcase and placed it on the table. It was white as chalk. He’s shown it to mayors and councilmembers and any number of officials, and he says everyone wants some, but until they can get federal assistance, or decide to pay for it themselves, there’s nothing to be done. "It’s great that they want it," he said, laughing bitterly. "It doesn’t do shit for getting it on the beach."

That may change eventually: in September the House passed an amendment proposed by Florida Representative Lois Frankel that would allow federal funds to go toward foreign sand, and Miami Beach is planning a small test project next year. But in the meantime, spurned by its neighbors and unable to buy sand abroad, Miami Beach turned inland, to a mine a hundred miles north. The sand from the northern counties was too dark and full of shells anyway, says an official with the county.

"They’ll be back," says Heard, the Martin County commissioner. "And they’ll receive spirited opposition next time they try it."

The mine is called Witherspoon and sits amid flat fields of pasture and scrub near the southwest shore of Lake Okeechobee. The water table is so high there that you strike it as soon as you dig, so in effect the mine is a pond, with a gray dredge floating in the middle sucking up sand from the bottom. On that late September day, the pond was still, mirroring the bright blue sky and high clouds, masking its 200-foot depth. The workers call it simply "the pit."

In a shed on the pit’s shore, Jacob Dampier scooped a small mound of sand onto a metal plate. With a spackling blade, deft and intent, sweating in the staggering heat, he cut it into four equal segments, squared their sides, leveled the top, and quartered them again. One brick he slid onto a scale, weighing out 350 grams, and slipped it into a ziploc bag. He pulled out a booklet, Munsell’s Soil Color, basically the Pantone chart for dirt, and found a match: value seven, chroma one, eggshell white.

"Sometimes it’s a little gray, sometimes it has an orange tint," Dampier said. "It depends where you are in the pit. But if it’s white, they love it. And you see how white that is? It’ll blind ya."

For 27 years Dampier has tested sand of an astonishing range and specificity: chunky sand for asphalt, finer sand for concrete, finest for masonry and glass. There’s a strict standard for volleyball courts, approved by an expert in Ontario, Canada, and a whole menu for golf courses: one blend for bunkers; another for topdressing; another, dyed green, for divot repair.

Since June, the mine had been running day and night producing sand for Miami Beach. White drifts lay beneath the tower where a machine sorts slurry from the dredge to fit exacting recipes of grain size. Tall hourglass cones lined the pit, and a dune stretched along the road where trucks sat idling, waiting to be waved out by a man standing under a rainbow beach umbrella. From here, three hundred trucks would drive 7,000 tons of sand to the parking lot of the Fontainebleau that day, and do it again the next, until over 300,000 tons have been placed on the shore.

In all, it’s projected to cost just under $12 million to patch 3,000 feet of Miami Beach’s waterfront. Sand prices have risen sharply since 2006, to an average of about $20 a cubic yard, according to Coburn’s database. Mined sand, sorted to bespoke criteria and requiring convoys of trucks, is more expensive still. Laurel Reichold, the Corps engineer managing the project, says at $60 a cubic yard, it costs twice what dredged sand would have.

Yellow all-terrain trucks complete the final leg of the journey, ferrying sand from the parking lot to the beach, escorted by men on ATVs wearing goggles and bandanas pulled over their faces. They turn onto a peninsula of fresh beach jutting out from the eroded shore and dump the sand into the sea. Bulldozers follow, grading the sand down to a gentle slope. The new beach, uniform and flat, is disorienting to be on, without markers for perspective or scale. But once the trucks leave and the waves get to work, it will seem as natural as the rest of the shore, covered in sunbathers and umbrellas.

"It’s gorgeous," said Elizabeth Wheaton, the city’s environment and sustainability director, picking up a handful of sand and letting it run through her fingers. "You just want to make snow angels in it."

Miami Beach has already begun to flood at high tide, and saltwater is pushing into the region’s aquifer. The city, like all South Florida, is doomed, says Hal Wanless, chair of the geological sciences department at the University of Miami. The state’s bedrock of porous limestone means that walls won’t stop the water; it’ll just seep up from below.

Evidence of just how radically changes in sea level can reshape Florida’s coast is everywhere, written in the sand. One of the sand deposits the Corps was eyeing offshore of Martin County was a beach about 10,000 years ago, when the sea was 60 feet lower. The Witherspoon mine was a beach 130,000 years ago, when the sea was 20 feet higher. A recent study of Antarctic ice melt predicted that if carbon emissions aren’t curtailed, by the end of the century the sea could rise by just over six feet, the high end of NOAA’s forecast, and the average elevation of Miami-Dade County. In 500 years it could rise as high as 49 feet. Well before then, the Witherspoon mine would become a beach once again.

The city, like all South Florida, is doomed.

The inertia of the climate system means that even if carbon emissions were halted tomorrow, the sea would continue to rise for centuries. With a Republican Party in denial about climate change, and a president who once called it a hoax perpetrated by China, we will likely lock in higher and faster rates of rise in the years to come. For cities on the coast it will be a slow catastrophe, involving myriad difficult decisions: whether to build infrastructure in an attempt to keep the water out, or whether to retreat from the coast, and if so, how to retreat without upending lives, economies, communities. One of the first decisions cities will face, one they’re already facing, is what to do about a shore that’s falling into the sea.

It will probably always be worth it for Miami Beach to go to absurd lengths in order to maintain its shore, right up until the moment the city sinks beneath the sea. Mayor Philip Levine, one of the first Florida politicians to raise the alarm about climate change, has spent $100 million building pumps and raising roads and plans to spend hundreds of millions more. But Florida has no income tax, so if cities are going to pay for the infrastructure needed to adapt, property values need to keep rising and tourists need to keep coming. Without a beach, why come to Miami Beach?

"The irony is, in Miami Beach and South Florida, the way to deal with rising sea levels is to build more condos," says Peter Zalewski, who tracks development through his site Condo Vultures. Just under 30,000 new units are planned or currently being built in Miami-Dade County, a region that already has more assets vulnerable to rising seas than anywhere in the world after Guangzhou, China. As long as Florida is trying to build its way out of climate change, the beach will need to be maintained, as a lure and a defense.

"You can have buildings or you can have beaches, but you can’t have both."

It won’t be worth it for other cities, however, especially if the federal government stops helping cover the cost of nourishment. The Army Corps’ mandate, Reichold says, is to protect property on the coast, and while recreation revenue is factored into the Corps’ cost-benefit analysis, that wouldn’t preclude building seawalls instead of nourishment if sand gets too expensive. Cities will face a choice: retreat, or build walls to keep the water out, destroying the beach.

"You can have buildings or you can have beaches, but you can’t have both," says Orrin Pilkey, founder of the Program for the Study of Developed Shorelines. He thinks buildings will win that calculation, and there will be a rush to build seawalls. It happened on a small scale after Hurricane Sandy, as billionaires erected metal plates and piled up boulders to defend their Hamptons mansions. As the water rises, more and more of the coast will become armored, the sand will wash away, and the shoreline will resemble a fortress of concrete and rock.

The beaches that remain would be amusement parks maintained at great expense, in cities like Miami Beach, Myrtle Beach, or Virginia Beach, perpetually rebuilt with sand from farther and farther out on the continental shelf, or inland from a once and future coast.

In late October, geologists from five East Coast states gathered at a lab in Palisades, New York, on the cliffs of the Hudson River. They were there to mark the opening of what is essentially a library of sand. For the two previous summers, a ship, the MS Thunderforce, had sailed from Miami to Boston, taking samples of the ocean floor, and now those samples had arrived at Columbia’s Lamont-Doherty Earth Observatory.

The survey was commissioned by the Bureau of Ocean Energy Management, which handles resources in federal waters, farther than most states have traditionally gone for sand. But as states have begun to run low on sand nearby, they’ve started turning to BOEM for help, says Jeff Reidenauer, the bureau’s marine minerals branch chief. With rising seas and stronger storms, it’s only a matter of time before states along the Eastern Seaboard are scrambling for sand to repair their shores, and the bureau wanted to know where to go. The survey began in the aftermath of Hurricane Sandy and goes by the apt acronym of ASAP, for Atlantic Sand Assessment Project.

In the lab, long tubes of sediment taken from the ocean floor lay displayed on tables. Researchers use the cores as time capsules, testing the stripes of clay and sand laid down over thousands of years to figure out what the planet was doing at the time. The people gathered in the lab that day, however, were mostly interested in the sand itself: its grain size, mineral type, how much of it there was and where.

The cores from the Thunderforce filled rack after rack inside a refrigerated warehouse adjoining the lab. Each plastic case was labeled by state, almost a wall for each: Massachusetts, New York, New Jersey, North Carolina, Georgia, Florida — 160 cores in all, with hundreds more on the way.

The shore crumbled as Matthew passed

The library was opening just in time. Three weeks before, a low-pressure disturbance that began off the coast of Africa reached the Caribbean, strengthened unusually rapidly, and slammed into Haiti as Hurricane Matthew, Category 4. It was headed for a direct hit on Southeast Florida but bent to the east, skimming the coast, and flooding North Carolina.

The storm sent powerful waves into the coast as it passed, washing away large sections of the shore in Georgia and South Carolina. In Florida waves washed over more than 50 miles of dunes. Beaches in St. Lucie County retreated dozens of feet, turning into cliffs. Brevard County had to rush sand onto the beach to protect homes left teetering over the sea. Jacksonville, in the middle of putting over 900,000 tons of sand on its beach, saw just as much wash away overnight. Near St. Augustine, waves punched through a dune and created a new inlet joining the Matanzas River with the Atlantic, while to the south, waves washed away dunes and concrete armor and chewed through a mile and a half of Highway A1A. Senator Bill Nelson promised the highway would be rebuilt and a new beach installed to protect it.

The damage is still being assessed, and where the sand to replace it will come from is unclear. Maybe it will be brought from a prehistoric beach by convoys of trucks, or from a Bahamian shoal, or maybe the counties will fall into another sand war. Or maybe it will come from one of the new deposits deep out on the continental shelf, mapped, catalogued, and archived in a walk-in refrigerator on the Hudson river.

Back at Miami Beach, work has paused for the winter. Sections of the new shore crumbled as Matthew passed but were soon repaired. Art Basel begins in a few weeks, and the completed beach in front of the Fontainebleau is ready to receive the dealers and collectors and partiers who will soon descend. Work will resume in the spring, with hundreds of trucks ferrying sand from the middle of the state to the shore, patching holes in a beach to postpone the day when it will inevitably vanish.

Editor: Michael Zelenko and Elizabeth Lopatto