Sand Wars!

Every summer, tens of millions of Americans slather on sunscreen and head to the beach. They roll out their towels, sink their toes into the sand, and enjoy the beautiful seashore. But what many vacationers don’t realize is that they’re being fooled. Nature isn’t responsible for most beaches as we know them—scientists and engineers are.

Up and down the coasts, beaches are eroding as waves, storms, and rising sea levels sweep sand out to sea. To stop beaches from disappearing altogether, geologists and engineers turn to beach nourishment—the process of building up beaches with sand from somewhere else.

A lot more than sand is at stake. Places like Miami Beach, Florida, and Santa Monica, California, depend on the money brought in by beach-going tourists to survive. And if beaches were lost to the ocean, the buildings along the shore would be next to go. So year after year, workers use tons of sand—mined inland or offshore—to rebuild beaches. There’s just one problem: With so much beach nourishment going on, Miami Beach and other seaside communities may soon run out of replacement sand.

Tens of millions of Americans rub on sunscreen and head to the beach every summer. They roll out their towels, sink their toes into the sand, and enjoy the beautiful seashore. But many vacationers don’t know that they’re being fooled. Nature isn’t behind most beaches as we know them. Scientists and engineers are.

Up and down the coasts, beaches are eroding. This happens as waves, storms, and rising sea levels sweep sand out to sea. To stop beaches from disappearing completely, geologists and engineers turn to beach nourishment. This process builds up beaches with sand from somewhere else.

A lot more than sand is at stake. Some places depend on money brought in by beach visitors. Miami Beach, Florida, and Santa Monica, California, need this money to survive. And if beaches were lost to the ocean, the buildings along the shore would go next. So year after year, workers use tons of sand to rebuild beaches. The sand is mined inland or offshore. There’s just one problem. A lot of beach nourishment is going on. That means beach communities may soon run out of replacement sand.

Beaches exist in a constant state of change. Each wave can bring in sand or take it away. Beaches often disappear during the winter, when big waves wash away sand. Smaller, gentler waves help rebuild the beaches every summer. Even high and low tides—the daily rise and fall of the seas caused by the pull of the moon’s gravity—change the way a beach looks.

But the drastic changes to coastlines today mainly come from sea level rise linked to climate change (see Swamped Beaches). As global average temperatures on Earth have increased, glaciers and ice sheets have begun to melt, adding water to the world’s oceans. The waters around Miami Beach—which lies only a few feet above sea level—are now rising by as much as a quarter of an inch per year. And the higher the ocean rises, the more sand it washes away.

Beaches are always changing. Each wave can bring in sand or take it away. Beaches often disappear during the winter. That’s when big waves wash away sand. Smaller, gentler waves help rebuild beaches every summer. High and low tides are the daily rise and fall of the seas caused by the pull of the moon’s gravity. Even the tides change the way a beach looks.

But today’s extreme coastline changes have a different cause. They come mostly from sea level rise linked to climate change (see Swamped Beaches). Global average temperatures on Earth are rising. Glaciers and ice sheets have begun to melt, and this adds water to the world’s oceans. Miami Beach lies only a few feet above sea level. But the waters around it are rising by as much as a quarter of an inch per year. And the higher the ocean rises, the more and more sand it washes away.

Most scientists believe that human activity is the main cause of climate change. Burning fossil fuels, for example, produces greenhouse gases that trap heat in Earth’s atmosphere. “The only way to slow down the disappearance of coastal communities is to slow down the rate of climate change,” says Robert Young, a coastal geologist at Western Carolina University in North Carolina.

Most scientists believe that human activity is the main cause of climate change. For example, burning fossil fuels produces greenhouse gases. These gases trap heat in Earth’s atmosphere. Robert Young is a coastal geologist at Western Carolina University in North Carolina. He says, “The only way to slow down the disappearance of coastal communities is to slow down the rate of climate change.”

All sand is different. Some sand is made of crushed minerals, like quartz and silica. Others contain a mixture of shells and pulverized coral. Certain sands even consist of old glass. Each type of sand has specific properties that make it better or worse for certain uses.

All sand is different. Some is made of crushed minerals, like quartz and silica. Other sand are a mixture of shells and broken coral. Certain sands are even made of old glass. Each type of sand has its own features. They make the sand better or worse for certain uses.

These differences are important to consider when it comes to beach nourishment. That’s because using the wrong type of sand can have consequences. Darker sand can absorb too much heat, making it uncomfortable to walk on. Sand consisting of big grains can erode unevenly. And sand made up of small grains tends to wash away too quickly.

The best sand for nourishing a given beach is generally found right offshore, says Spencer Rogers, a coastal engineer at the North Carolina Sea Grant. It’s more likely to be made from the same material as the sand on the beach. But the supply of those offshore deposits isn’t infinite.

These differences are important in beach nourishment. Using the wrong type of sand can have unwanted effects. Darker sand can soak up too much heat. This makes it uncomfortable to walk on. Sand with big grains can wash away unevenly. And sand made up of small grains tends to wash away too quickly.

The best sand for nourishing a beach is usually right offshore, says Spencer Rogers. He’s a coastal engineer at the North Carolina Sea Grant. This sand is often made from the same material as the sand on the beach. But the supply of sand offshore isn’t endless.

Miami-Dade County pays to dredge, or suck sand from the bottom of the ocean, just offshore and dump the sand onto its beaches (see Sand Collector). But in 2015, the county discovered that it had used up its offshore supply.

One solution was to dredge just offshore from two counties north of Miami. That area has a type of sand similar to what is found on Miami’s beaches. But those counties were determined to protect the precious natural resource for their own beaches. Public officials protested, and Miami backed off. It was the most recent battle in what locals in the area refer to as the “sand wars.”

Offshore sand can be dredged, or sucked from the bottom of the ocean. Miami-Dade County pays to dredge just offshore and dump the sand onto its beaches (see Sand Collector). But in 2015, the county found that it had used up its offshore supply.

One solution was to dredge just offshore from two counties north of Miami. That area has sand like the sand on Miami’s beaches. But those counties wanted to protect the valuable natural resource for their own beaches. Public officials protested, and Miami backed off. It was the most recent battle over sand in the area. Local people call the clashes the “sand wars.”

Eventually, Miami found a source of sand inland, which workers dredged from the bottom of a pond. More than 300,000 tons of this sand—about 9,000 dump trucks’ worth—were needed to restore just 910 meters (2,986 feet) of Miami Beach. This sand will last a couple of years before more nourishment is needed.

Finally, Miami found a source of sand inland. Workers dredged it from the bottom of a pond. More than 300,000 tons of this sand were needed to restore just 910 meters (2,986 feet) of Miami Beach. That’s about 9,000 dump trucks’ worth. This sand will last a couple of years before more nourishment is needed.

“Coastal sand is going to become as important as water for beachfront communities that want to keep building their beaches,” says Young. “Because if these places don’t keep nourishing their beaches, they will disappear.”

For now, beach nourishment still makes economic sense for places like Miami Beach. It may cost millions of dollars, but the tourism it sustains brings in far more money. Poorer coastal areas—and places without nearby sand deposits—will be hardest hit by rising waters and disappearing beaches.

“In 100 years, the map of the coast will be a different map,” says Young. “No question about it.”

“Coastal sand is going to become as important as water for beachfront communities that want to keep building their beaches,” says Young. “Because if these places don’t keep nourishing their beaches, they will disappear.”

Beach nourishment may cost millions of dollars. But for now, it still makes economic sense for places like Miami Beach. It supports tourism that brings in far more money. Poorer coastal areas will be hit harder by rising waters and disappearing beaches. So will places without nearby sand sources.

“In 100 years, the map of the coast will be a different map,” says Young. “No question about it.”