Seashells are not a souvenir: Scientists explain why it's better to leave them on the beach.

It's a summer ritual. Like eating a cold watermelon at dusk, picking figs straight from the tree, or lying on a blanket in the middle of the night watching the Perseids pass by. Collecting shells and snails by the seashore is one of the most typical August traditions. But it comes at a price, it always has.

“Let's assume the following,” says Michal Kowalewski, a researcher at the University of Florida (United States) specializing in the study of invertebrates : “There are, annually and almost certainly worldwide, around 10 billion visits to beaches. And let's say one shell is collected for every 100 visits, which sounds small, but we'd still be talking about 10,000 tons of shells disappearing from beaches every year.” This is as if three Olympic-sized swimming pools were filled to the brim. It seems like a small and innocent gesture, but the rise of mass tourism on Mediterranean beaches is irreversibly altering their ecosystems, and now lugging a summer souvenir home is leaving an ever-deeper mark.

Scientists have been warning about this for years. A study by Kowalewski and researchers from the University of Barcelona , published in the journal PLOS One in 2014, already showed a drastic decrease in the number of shells present on Larga Beach in Salou (Catalonia). The authors compared two series of systematic samplings carried out in the same location 30 years apart: the first between 1978 and 1981, and the second between 2008 and 2010. They found that the presence of shells decreased almost threefold during the study period.

This decline coincided with an almost parallel increase in the number of tourists, which increased 2.7-fold during that period. However, the physical conditions of the environment—such as wave energy and climate—remained stable. Furthermore, the ecological indicators extracted from the study of shells—species dominance, size distribution, frequency of shell perforation by predators—were constant over the years. This indicates that there have been no substantial changes in the dynamics of mollusk populations or in the basic structure of the local marine ecosystem . So it seems that humans are to blame.

“More tourism means greater urbanization of the coastal area and increased boating activity,” Kowalewski points out. He adds: “The use of machinery for beach cleaning is also progressively increasing, and this is significant because it involves machinery passing over the sand, pulverizing the shells.” Then there's the matter of harvesting.

"Of course it's not harmless," says Jordi Martinell Callicó, another of the study's authors, who has also spent his entire life on the beach chosen for sampling and has seen the region's progressive deterioration firsthand. "The pressure on the coastal zone is very strong," he adds.

“I agree that taking a single shell isn't a big deal,” says Kowalewski. The problem is that billions of people, visiting beaches each year, often take entire buckets of them. “They put them away at home, but over time, most of those shells end up in the trash or landfills,” he warns.

For decades, this has also been technically prohibited in Spain. The Coastal Law establishes that sand, stones, shells, mollusks, and beach fossils are public property and that their unauthorized extraction is illegal. While taking one or two as a souvenir is not actively prosecuted, it can carry fines of between €500 and €3,000.

An essential environmental function

In the living room, they're just decoration, but on the beach, shells perform multiple ecosystem services and play an essential environmental role. "They're not there by chance: they're part of the natural ecosystem that keeps our beaches alive and stable," explains Fernando García Guerrero, one of the curators of the malacology collection at the National Museum of Natural Sciences.

The experts consulted detail that one of the main functions of shells is the physical stabilization of beaches . “Each shell, no matter how small it may seem, helps keep the sand in place, slowing its wash with each tide. Thanks to them, beaches retain their shape, firmness, and ability to resist erosion,” explains García.

“When shells dissolve, they also affect the acidity of the water, as they contain calcium carbonate, which modifies the ocean's pH,” explains Martinell. This helps recycle calcium and other elements back into the sea, helping to maintain vital cycles within the water, including the generation of new shells.

Shells, in turn, provide shelter and habitat for many organisms. Algae, seagrasses, hermit crabs, small invertebrates, and even shorebirds use them as homes or as building materials. Some birds even use them to sharpen their beaks. It's indisputable: the loss of shells alters the physical, chemical, and biological balance of beaches.

Better to leave the shell where it is

At this point, the impact of human activity on the coast seems inevitable. “However, we can still minimize our footprint while we walk,” Kowalewski argues. The scientist says he would advocate for the simplest and at the same time most complicated of all: environmental education. “I think that's the best way to begin mitigating the problem,” he opines. Martinell agrees: “We need to raise awareness among vacationers so they are careful, respect the beach environment, and don't destroy it. Taking a shell may seem like nothing. But it's not necessary; it's better to leave it where it is.”

“The good news,” García notes, “is that enjoying the beach and caring for it are not only compatible, but should go hand in hand.” Instead of taking the shells home, the scientist suggests observing them, photographing them, or simply admiring them. “The experience doesn't lose value by not having a physical object as a souvenir; on the contrary, we gain a connection with nature,” he says.

He also mentions that, when visiting a beach, it's important not to disturb the dune vegetation, avoid walking off marked trails, pick up trash, and follow the instructions of environmental authorities. "Taking care of the coast doesn't mean giving up enjoying it," he reminds us. He then adds: "On the contrary, it means learning to truly value it. Because what we protect, we conserve. And what we conserve, endures."