The Mediterranean Sea accounts for less than 1% of the world’s ocean surface water, yet it contains roughly 18% of global marine biodiversity. This semi-enclosed sea is home to 150 million people along its coastline\u2014a number roughly equivalent to Russia’s population. Each year, it sequesters 17.2 million metric tons of CO2, making it a vital but often overlooked carbon sink. According to journalist Manuela Callari, who has reported extensively on the region for Mongabay, the Mediterranean’s health is crucial not just for the 150 million residents but for the entire planet.<\/p>\n
“The Mediterranean Sea is unique because it’s a semi-enclosed sea, connected to the oceans in a very subtle way. It takes about a century for a drop to get through the strait and into the ocean,” Callari explains. This slow exchange makes the basin particularly vulnerable to pollution, overfishing, and climate change. The Mediterranean’s average surface temperature has already risen by 1.2\u00b0C (2.2\u00b0F) since the mid-1980s, as shown by satellite data.<\/p>\n
Among the many pressures on the Mediterranean, overfishing is one of the most severe. Illegal fishing methods like trawling destroy the seabed, and plastic pollution is another major issue. According to some estimates, the Mediterranean absorbs at least 229,000 tons of plastic each year\u2014and possibly up to 570,000 tons. This plastic breaks down into microplastics, entering the food chain and harming ecosystems.<\/p>\n
One telling example of overfishing involves the purple sea urchin (Paracentrotus lividus<\/em>). These marine invertebrates are the primary ingredient in a popular tourist dish: spaghetti ai ricci di mare. In regions like Puglia, Sicily, and Sardinia, sea urchins have been eaten raw or with spaghetti for centuries. However, soaring demand from tourists and cooking shows has pushed illegal harvesting, even within marine protected areas (MPAs).<\/p>\n A study conducted by staff at the Gaiola MPA near Naples and researchers from Genoa found that inside the MPA, sea urchin density reaches about 90 individuals per square meter. Outside the protected area, it plummets to 0.5\u20130.2 individuals per square meter. “There are areas where they don’t exist anymore,” Callari says. Poachers raid MPAs at night because few sea urchins remain elsewhere. Even when caught, penalties are often minimal. Callari notes that judges in busy courts like Naples may prioritize violent crimes over environmental offenses, issuing fines as low as \u20ac500 with no jail time.<\/p>\n Sea urchins are crucial for maintaining healthy marine ecosystems. They graze on algae, preventing any one species from dominating and becoming a monoculture. They also serve as food for larger predators like sea breams. Removing urchins triggers a cascading effect: predators leave, algae overgrows, and the entire ecosystem collapses into a barren state. Conversely, overfishing predators can cause urchin populations to explode, creating underwater deserts\u2014a problem now seen in parts of Spain.<\/p>\n On the island of Lampedusa, over 90% of fishers have shifted from fishing to tourism because fish stocks have declined so sharply. “There are no longer fish to be caught,” Callari reports. This economic pressure further fuels unsustainable practices.<\/p>\n In response to these crises, Italy has launched an unprecedented effort to map its entire underwater coastline using deployed sensors and satellite imaging. The project is part of the Marine Ecosystem Restoration (MER) initiative, funded by the European Union’s Recovery and Resilience Plan (PNRR) with millions of euros. The goal is to create a comprehensive map of Posidonia oceanica<\/em>, a seagrass species unique to the Mediterranean.<\/p>\n Posidonia meadows are “absolutely vital” to the Mediterranean ecosystem. As a plant, it uses photosynthesis to capture carbon, but unlike forests, when its leaves die, they settle on the seabed and form a dense mat called “matte.” Because oxygen is scarce at the seafloor, bacteria cannot decompose the organic matter, so the carbon remains locked away. “The Posidonia meadows can capture up to 35% more carbon than a tropical forest,” Callari emphasizes. If these meadows die off, that stored carbon could be released back into the atmosphere, accelerating climate change.<\/p>\n Posidonia is very slow-growing\u2014it can take centuries to recover from damage. It reproduces both by seeds and through rhizomes (underground stems) that create dense structures stabilizing the seabed and protecting coastlines from erosion. Threats include illegal trawling, pollution, heat waves, and boat anchoring, which can leave scars that persist for decades.<\/p>\n Previous maps of Posidonia were 20 to 30 years old and often inaccurate. The new mapping project has already discovered meadows at depths much greater than the previously thought maximum of 5 meters, expanding the known range. It has also identified areas where meadows have been damaged, informing restoration efforts. Researchers are testing various replanting methods in Genoa, Naples, Campania, and Sardinia.<\/p>\nEcological Consequences of Urchin Depletion<\/h3>\n
Mapping and Protecting Posidonia Seagrass Meadows<\/h2>\n
The Vital Role of Posidonia in Carbon Capture<\/h3>\n
Italy’s Ambitious Marine Ecosystem Restoration Project<\/h3>\n