It’s an innocent enough vacation activity. Everyone loves to stroll along the beach, collecting pretty seashells as mementos of a wonderful trip. It’s a peaceful and relaxing pastime, not to mention a little romantic. Well, stop. Just stop it.

That’s the recommendation of a new study which says that the global rise in tourism means that too many people are carting away too many seashells. Innocuous as shell collecting seems, this practice is actually harming beach ecosystems.

Tourism around the world has increased four-fold in the last three decades. According to the journal PLOS ONE, this vacationing surge has spurred noticeable global acceleration in the disappearance of shoreline shells. The study points an unforgiving finger squarely at tourists.

The loss of all these seashells leads inexorably to increased beach erosion and a marked decline in the abundance and diversity of organisms that rely on these shells, says the study.

“Shells are remarkable in that they serve multiple functions in natural ecosystems, from beach stabilization to building materials for bird nests,” lead study author Michal Kowalewski said in a press release.

How Researchers Narrowed it Down to Seashell Collectors

How can picking up simple seashells cause an ecosystem domino effect? The study, conducted on coastal Spain’s Llarga Beach from 1978 to 1981 and from 2008 to 2010, looked carefully at a variety of issues before coming to this conclusion.

During the period of the study, researchers from the University of Florida and the University of Barcelona surveyed Llarga Beach several times each month. By looking at hotel records in the area they determined that beach tourism increased by 30 percent. At the same time, the number of seashells on the beach dropped by more than 60 percent.

Shells, more plentiful in the winter when tourism was down, were significantly fewer in the summer when more beach visitors were present.

No other human-related factors appear to have influenced the shell loss. Llagra Beach proved a useful study site because it wasn’t altered by human activity appreciably in any way over the course of the multi-decade study. Additionally, researchers observed no environmental or ecosystem changes that would affect the number of shells one would expect to find on the beach.

Tourists are the primary cause of the seashell loss, the study concludes.

Why Shells Matter to the Marine Ecosystem

It might seem that seashells are merely the cast off protective armor of sea creatures that no longer need them. What’s the harm if people remove them from the beach and take them home? Quite a lot, potentially.

A wide variety of marine organisms depend on discarded seashells to survive. Sponges, seagrass, algae and other small organisms attach themselves to shells and live there. Fish use shells to hide from other sea creatures who want to eat them. Hermit crabs love to use empty snail shells as their own portable apartment homes.

Mollusk exoskeletons, such as clam and oyster shells, serve another important purpose. As they dissolve, they recycle calcium carbonate back into the ocean environment where it is ultimately used by other creatures to develop their own protective shells.

What Can Be Done?

“Although significant research has been done on the impacts of human activity on live shellfish, including, recreational harvesting and curio collecting, we are still lacking rigorous studies estimating the scale of shell removal by humans,” Kowalewski said.

While there are currently no studies on a worldwide level of this phenomenon, what’s concerning about this study is that coastal Spain’s Llagra Beach is only a small, marginally trendy vacation locale.

“Although a popular destination, the beach is not a major tourist hot spot, and the shells found there are not beautiful, diverse, or valuable to collectors,” Kowalewski noted. One can only imagine the amount of shells that must be disappearing from the major beaches and coastlines of the world.

Some countries already recognize the harm tourists can do if they remove too many shells. The Bahamas, for example, already limits the number of shells visitors may export. Perhaps more such limitations should be considered. The authors of this study certainly feel that way.

“Humans may play a significant role in altering habitats through activities that many would perceive as mostly harmless, such as beachcombing and seashell collecting,” Kowalewski said. “It is important that we continue to investigate the more subtle aspects of tourism-related activities and their impact on shoreline habitats.”

Imagine multiplying exponentially the level of shell losses documented at little Llagra Beach. Scientists say it’s worrisome.

Tourists, take note. Everything we do on vacation can have unintended consequences. Tread lightly. Leave nature alone. You don’t need those shells as much as marine creatures do.

By: Susan Bird

Photo credits: Thinkstock