What would you guess is the star attraction of Miami Beach? If you said, "the beach," well, hey. You're making a lot of sense.

That beautiful beach, like the tony hotels that overlook it, was built by the hand of man. And it has to be re-built on a regular basis. For that, you need sand — the right kind of sand, and lots of it. Finding that sand has become a big deal for public officials in Florida coastal towns, where the beach — like it or not — is infrastructure. The Verge's Josh Dzieza took a closer look this month (see: "Sand's End: Miami Beach has run out of sand. Now what?").

"To the casual observer," wrote Dzieza, "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," Dzieza reported. "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."

After depleting local offshore sand reserves, Miami Beach is looking elsewhere — and every option has drawbacks. There's beautiful sand for sale in the nearby Bahamas, but federal law won't allow government funds to pay for sand imported from outside the United States. There's sand in federal waters north of the city, but beach communities closer to those deposits are fighting Miami Beach for the right to use it. So for now, Miami Beach is buying sand from an inland mine on near Lake Okeechobee. (A hundred and thirty thousand years ago, the Okeechobee mine, now 20 feet above sea level, was a beach itself.)

For Miami Beach, where the local economy depends on the city's strip of gleaming white sand, buying a new beach every year will probably remain a practical path. For other communities on the ocean front, the economics may not work out — they may give up on the beach and build seawalls instead. But no matter what, sand — all kinds of sand — will remain a high-value commodity worldwide, needed not just for beaches, but for concrete and other construction and industrial uses. "Rob Young, director of the Program for the Study of Developed Shorelines at Western Carolina University... foresees a future of rising costs and conflict over diminishing sand," the Verge reported. Said the professor: "If you want to invest, buy a dredge."