Why seashells are getting harder to find on the seashore

In 1973, when Melissa Greene was in 6th grade, her parents bought the first condo at a new Florida beachfront development on Hutchinson Island on the southeastern Atlantic coast.

The first time she and her siblings ran down to the wild shore, they were shocked by the contrast to their earlier beach trips to Daytona, a people-packed spectacle of cars and cruising. On Hutchinson, the spectacle was the seashells.

Every tide left a wrack line of conchs and whelks, nutmegs and tulip shells, shark’s eyes as big as a half-dollar and brown-speckled cowries as large as Greene’s hand. Down the beach, a driftwood forest captured still more shells, along with starfish and crabs and marine egg cases of all kinds.

Greene and her family will soon mark a half-century’s ownership at Ocean Village, now a community of 1,200 homes. Today, on the same stretch of beach, she rarely finds the large, intact shells that were common in her childhood.  

“It’s a startling difference,” she says. While a big storm can still wash up marine life and scree, “what you don’t see any more are the deep piles of whole shells, quarter-sized and above, and the larger shells that we saw for years.”

Among the most revered natural objects throughout human history, seashells encapsulate both the surprise and wonder still promised by a trip to the beach—and the profound changes underway on our coasts.

From abalone on the west coast to conchs and whelks on the Eastern Seaboard, some of the largest and best-known marine mollusks—the animal architects that build seashells from calcium carbonate in seawater—have declined under fishing pressure. They are also harmed by rising ocean temperatures and acidifying waters, and by other pollution and runoff from the land. And they can be displaced by the severe erosion caused by inlets and jetties—a persistent problem on Hutchinson Island—as well as the efforts to repair eroded beaches by restoring lost sand.

(Read about how the seashell trade is affecting marine life.)

But marine mollusks, which have survived Earth’s changes for 500 million years, also prove to be models of resilience and our ability to fix what’s broken, says George Buckley of the Boston Malacology Club. Before passage of the Clean Water Act in 1972, when he was a young club president, Buckley watched beloved mollusks and seashells extirpated by industrial and sewage pollution on the Boston Harbor Islands. Today, “the mollusks have repopulated,” he says. “You find mollusks and you find shells.”

Fishers (and tourists) v mollusks

On beaches seeing record tourism numbers, more people can mean fewer shells. “It is not so much individual collecting as the many ramifications of massive tourism,” says the paleobiologist Michal Kowalewski at the Florida Museum of Natural History. “Mass tourism means more boats, more beach maintenance, more machinery, all contributing to changes in shorelines.”

Like suburbanites obsessed with trim green lawns, many beachgoers have developed a preference for immaculately groomed sand. Manicured beaches can mean heavy machinery that rakes the sand with sharp tines. As the sand-tillers sift out plastic, cigarette butts and other human detritus, they also scoop up marine life, shells, and driftwood.

Florida limits mechanized beach cleaning equipment during nesting season for threatened and endangered sea turtles. But marine mollusks and other invertebrates don’t draw the same concern—or research dollars—as animals like sea turtles whose eyes are big, soulful, and not mounted on tentacles. Ecologists have found that the Red List of the International Union for Conservation of Nature—the official gauge for the staggering decline of animals now underway around the world—severely underestimates loss of invertebrates, which make up an estimated 97 percent of all creatures.

Research funding for commercially important species means that scientists know the most about the mollusks we eat. Channeled whelk and knobbed whelk, once ubiquitous on the beaches from Cape Cod to Cape Canaveral, became multi-million-dollar fisheries faster than they could be regulated. Researchers have found female whelks are being harvested before they have a chance to reproduce.

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The same is true for horse conchs, which build the largest shells in the Northern Hemisphere. The spindle-shaped shells can grow as long as two feet; their enormity led Florida lawmakers to name horse conchs the state seashell in 1969. Yet sizes documented in historic beach photos are no longer seen. Researchers have found that a century of unregulated harvesting has put them at risk of extinction.

Farther south, queen conchs, which build glossy pink shells the size of a football, are so evocative of the Florida Keys that people born on the islands are called “conchs.” But the queen conch population there collapsed in the mid-twentieth century and has never rebounded, despite Florida’s ban on commercial conch fishing since 1975 and on all harvesting since 1986. The queens’ losses have now spread to the Bahamas and the Caribbean. Researchers warn that the once-massive conch herds of the Bahamas—which exports much of the conch meat consumed in the United States—have now thinned below the minimum number the animals need to breed.

Lessons of the past

Quantifying the status of the tens of thousands of other mollusks in the sea is a challenge given the lack of baseline data before the mid-20th century. Paleontologist Susan Kidwell of the University of Chicago pioneered the use of “live-dead studies” to compare shell accumulations from the past, discovered in ocean sediments, to populations of shelled animals living today. In areas with human stressors such as sewage outfalls, seafloor dredging or significant land-use changes, the present populations do not measure up. In some cases, they’ve vanished.

Kidwell linked the collapse of a vast marine ecosystem that once thrived off Southern California’s continental shelf, for example, to the introduction of cattle by Spanish colonists. Few sediments flowed from the region’s coastal prairies prior to the 1770s, fossil records from the seafloor show. A century’s unmanaged grazing transformed that ecosystem, sending megatons of sediment from rivers to the sea. Brachiopods and scallops that had lived off the shelf for 4,000 years could not tolerate the silt. They died out. Mud-loving clams took their place.

Live-dead studies are also beginning to show how disastrous warming ocean temperatures can be for native marine mollusks. A team led by Paolo G. Albano at Italy’s Anton Dohrn Zoological Station found a near 90 percent loss of native populations in the soft shallows off Israel in the Mediterranean Sea, one of the fastest-warming parts of the global oceans.

The studies can be “like writing obituaries,” Kidwell says. But they can also offer insights into recovery and resilience. Kowalewski and colleagues conducted live-dead studies in the seagrass meadows of the Big Bend in Florida’s northern Gulf, one of the least-disturbed coastal ecosystems in the United States. Collecting and analyzing more than 50,000 shells, they found that mollusk populations living in Big Bend meadows today look much like those that lived during previous centuries.

Kowalewski hopes to replicate the research in one of the regions where Florida is losing seagrass. If manatees are dying, it stands to reason that other animals that rely on the grasses are in trouble, too.

For the love of shells

On Sanibel Island on the southwestern coast of Florida, mollusks burrow, bubble and scoot along the wet sand in a colorful parade of seashells. Twenty-five years ago, Sanibel became the first city in the U.S. to ban “live shelling,” the practice of collecting and killing mollusks for their shells. The move to protect the individual lives of soft-bodied mollusks seems almost quaint given ocean warming and other “crude realities of the changing world,” acknowledges José H. Leal, science director and curator at Sanibel’s Bailey-Matthews National Shell Museum.

But helping beachgoers appreciate the animals inside the shell as much as the polished exterior turns out to be a crucial step toward helping them understand what’s happening in the sea, Leal says. “Even at the subliminal level, if people understand the complexity of these animals and their importance, they also realize the need to protect ocean ecosystems.”

Delaware’s state parks are among increasing numbers of state and national parks taking so-called low-impact beachcombing a step further: asking visitors to leave empty shells alone, too. At Delaware Seashore State Park, signs advise visitors to “Leave shells where they lay or snap a photo of a marine critter in the sand. After all, the point of enjoying nature is because it is in a natural state.”

The initiative, launched in the pandemic as people descended on the beaches in record numbers to escape lockdown, builds on the “leave no trace” ethic that Delaware has worked on for decades, says state parks director Ray Bivens, who started with the agency as a naturalist. Left to accumulate on the beach, shells are reused by hermit crabs, provide habitat for other animals, and serve as camouflage for tiny bird eggs and babies.

“For the majority of people, they really want to do the right thing,” Bivens says. “Those ecological values make sense, even if they’ve been beachcombing for their entire lives.” 

Resisting the urge also means another beachcomber, maybe a child, will get to experience the wonder of finding a shell.