What Looks Like Dirt is Posidonia (and It's Vital for the Sea)
The brown leaves on the shoreline are not waste. They are the marine ecosystem of the Mediterranean. Why removing them is a mistake that costs you in a few years.
You arrive at the beach at 8, see the lifeguard with the tractor raking. On the ground, a brown carpet of intertwined leaves. "Good thing they're cleaning," you think. Too bad what they're removing isn't dirt, but Posidonia oceanica: a marine plant endemic to the Mediterranean, crucial for the coastal ecosystem's life. Removing it causes three damages: destroys the habitat of 400 species, accelerates beach erosion, releases CO2 stored for centuries.
What it is, exactly
Posidonia is not an algae. It's a true plant, with roots, rhizomes, and flowers, living only in the Mediterranean between 1 and 40 meters deep. It forms real underwater meadows — those in Salento are among the largest in Italy, and some are over 100,000 years old. They are living organisms older than the pyramids, older than any human civilization.
In summer, when storms tear off the old leaves, they float and wash ashore. On the shore, they accumulate in the form of "banquettes" — the brown intertwined structures you see. Over time, these banquettes do three things.
1. Protect the beach from erosion
The banquettes are natural barriers against storm surges. They absorb the wave's energy before it reaches the sand. ARPA Puglia studies show that beaches cleaned mechanically every year lose up to 2 meters of sand per season. Those left with the banquettes maintain the coastline.
«Posidonia is the beach's immune system. Removing it, we remove the defense.»
2. They are habitat for 400 species
In the underwater meadow live cuttlefish, seahorses, bream, pipefish, mollusks, sea urchins, starfish. When posidonia disappears, so do they. That's why in many areas of Salento you no longer find the bream of the past: it's not overfishing, it's habitat loss.
3. Store CO2 like a forest
A hectare of posidonia meadow absorbs 15 times more CO2 than a hectare of Amazon rainforest. The carbon is fixed in the sediments for millennia. When we burn the banquettes on the beach — something still practiced in some areas — we release carbon stored for centuries.
Why it was removed for 30 years
For reasons of pure tourist aesthetics. In the 1980s, with the explosion of mass beach tourism, "clean beach" became synonymous with "beach empty of posidonia." Concessionaires removed everything every morning. It was illegal, but no one checked.
Today things are changing. Posidonia oceanica is a protected species under the European Habitat directive since 1992. In Puglia, since 2021, mechanical removal is banned on all public land. Concessionaires can now only move the banquettes, not remove them.
What to do when you find it
Nothing. Posidonia is harmless, it doesn't sting, it doesn't smell (unless after days of intense sun on large accumulations). You can walk on it, lie next to it, even on top of it. Some stretches of Salento coast like Frassanito, Alimini, Campomarino, have permanent banquettes. They are proof that the beach is working, not that it's dirty.
When it's not posidonia
Beware: if you find green-purple filaments on the shoreline, that's Caulerpa taxifolia, an invasive alien algae. It usually doesn't reach the shore, but if you see it, report to ARPA (082.58.XX.XX). If you find brown spheres of intertwined fibers (called "Neptune's eggs" or "egagropili"), those are also posidonia — just in a compact form created by currents.
Everything you see that's brown-beige, intertwined, fibrous: it's life. It's the reason why tomorrow morning the beach will still be there.