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Formentera Island


Conservation benefit: Seagrass protection

Community benefit: Mobile app that lets boats avoid anchoring on seagrass

Date Approved: 02.2020


This project protects seagrass, which traps more CO2 than any other marine ecosystem, slowing global warming.

Posidonia oceanica is a seagrass endemic to the Mediterranean Sea—an unsung hero of biodiversity that creates huge, uniquely important ecosystems. Posidonia beds grow over centuries, forming beds several meters high and sinking deep roots. These meadows teem with fish, mollusks, starfishes, crustaceans, and plankton. The meadows protect the coast and beaches against erosion and keep the water clear. Local people depend on them because they are crucial to fishing and tourism. In fact, all of us depend on seagrass, because seagrass ecosystems are the most efficient carbon sink of any ecosystem on the planet. They trap carbon and keep it out of the atmosphere for thousands of years.

Alarmingly, recent studies suggest that in the western Mediterranean, Posidonia beds have declined by 34% over the last 50 years. This catastrophe has multiple causes, but trawling and anchoring are the most destructive of the human-caused factors.

This project would help protect the largest and oldest Posidonia meadow in the Mediterranean Sea, by preventing damage from anchors. The seagrass is in the Natural Park of Ses Salines. In the summer, around 4,000 boats anchor each day in the marine park and its surroundings, destroying large areas of seagrass.

In many instances, boat crews don’t realize that they are dropping anchor on seagrass, which may not be visible in deeper water. But there’s good news: There’s an app for that.

The free app, which has been downloaded more than 4,000 times, lets boat crews know exactly where seagrass is so they can avoid it. It relies on exquisitely accurate (within one meter) maps of the seagrass beds, made from data collected by lateral-scan sonar, drones, and human divers. The mapping has identified most of the Posidonia beds (totaling 18,904 acres) around Formentera Island, the smallest inhabited Balearic Island in the western Mediterranean.

Our nonprofit partner, the Vellmari Association, will use a Seacology grant to finish mapping seagrass around Formentera and make this valuable information available to everyone. The goal is to keep gathering data and eventually include Posidonia meadows in other parts of Spain, France, Italy, and beyond.

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