Posidonia: The Great Unseen Forest That Protects the Balearic Coastline

How did you become professionally involved in posidonia conservation?

I’ve been working in the public sector for more than 20 years, first through the Posidonia Atlas project, which was the first of its kind in the Mediterranean to map these seagrass meadows. Then I started to get involved in the ecological buoy zones, to prevent boats from mooring on posidonia in areas with high boat traffic. Over time, I helped to create the Posidonia Monitoring Service, which was founded in Formentera in 2012–2013, and has since expanded to all the islands. My involvement is professional, but also personal: I feel a special connection with the sea. When I go diving among posidonia, I feel at home.

How exactly does the monitoring service work?

There are 19 vessels that monitor moorings every day, but there’s more to it than that. It’s a broader system that includes an information centre that you can call to check whether you can moor in a certain zone or to report moorings on posidonia. We also work with the Guardia Civil and environmental agents who have the power to give out fines. Our approach is preventive: we inform people, help them to moor properly and raise awareness at sea. Moreover, together with funding from sustainable tourism tax and backing from the Balearic Islands Agency for Tourism Strategy (AETIB), we’ve created the Posidonia Atlas, which details the precise location of the meadows. Thanks to this mapping, apps have been developed that are incredibly useful, especially for large vessels, which have significantly reduced their impact.

Some people still believe that posidonia is a type of seaweed. What makes it so special and what role does it play?

Posidonia is not seaweed, but a plant that, like dolphins, was once land-based and then returned to the sea. We use the term ‘seagrass meadows’, which we also call underwater forests or jungles due to their size and biodiversity. In the Balearic Islands, these meadows take up around 650 km², almost as much as pine forests. They create underwater ecosystems in places like Alcudia, Pollença and Palma; you can’t see them, but they’re fundamental. Seagrass has numerous benefits. It produces oxygen, essential for marine life as well as for us. It’s home to hundreds of species, which even has an impact on local fishing. It improves water quality by acting as a natural filter. It also creates sand: around 80% of the sand we see on Es Trenc comes from its microfauna. Moreover, it protects the coast from erosion and captures large amounts of carbon. It forms calcareous reefs that act as a powerful natural infrastructure against climate change, absorbing up to 15 times more CO₂ than a tropical forest.

How does climate change affect you and why is it such a concern in this context?

The Mediterranean is an enclosed sea, with little water renewal. As a result, it’s heating up faster than the oceans, which is of great concern to the scientific community. Posidonia starts to become stressed at 28–29°C, and at 31°C it no longer germinates. In this situation, we would not only lose biodiversity, but also coastal protection. Without posidonia, sand would disappear, the coastline would recede and one of the main tourist attractions in the Balearic Islands would be lost. Moreover, its natural reefs cushion the force of storms and reduce wave power. This means posidonia is not just suffering the effects of climate change, but it’s also one of our best tools to mitigate them.

Does it also have consequences for the economy and tourism?

Yes, and they're very direct. In places that have lost this seagrass, such as Bodrum (Turkey) and Tarragona, the water has become murky, fishing has declined and coastal erosion has gotten worse. In Cala Millor, for example, we’re working on a project called ‘Life Adapt Cala Millor’ together with hotel owners in the area. They’re worried themselves because they can see the sand disappearing. They’ve calculated the cost of replacing it, and it’s very high. This is why we treat posidonia as part of the dune system. Its disappearance would affect thousands of jobs and the tourism model itself.

What’s the current condition of these meadows in the Balearic Islands?

Fortunately, seagrass in the Balearic Islands is in relatively good condition. We don’t have large industrial infrastructure or as much strain as in other areas of the Mediterranean. The main impact comes from anchors and some outfalls. Even so, thanks to the protection order, the efforts of the monitoring service, the work of civil society and the general awareness of the public, we’re seeing results. In fact, I believe the Balearic Islands are leading marine conservation in the Mediterranean.

Which areas are under the greatest threat or require special attention?

There are critical areas. The so-called shallow bays, such as Portocolom, are enclosed areas that are highly sensitive in terms of ecology. In Ibiza, Talamanca and Port Roig have enormous strain form boats, and buoy zones have yet to be established. And in the Bay of Palma, in front of the cathedral, the impact of outfalls and large vessels, including aircraft carriers and cruise ships, is very high. This area needs urgent restoration measures.

What measures have proven to be most effective so far?

Three elements have been key. Firstly, mapping and digital tools developed with funding from sustainable tourism tax and other sources such as Next Generation EU. They’ve been instrumental in improving mooring practices, especially for long boats. Secondly, the posidonia protection order, which is the most advanced in the Mediterranean. And thirdly, the involvement of civil society: from schools to diving clubs. We have, for example, the Aula del Mar (‘Sea Classroom’) in Portitxol, a school on posidonia. We have also created Xarxa Posidonia, a network of volunteer diving centres that monitor the condition of the meadows. This is all part of a widespread, powerful operation.

What's still to be done?

A lot. We need to reduce discharge to the sea, improve the management of outfalls, continue installing buoy zones in sensitive areas and, above all, create a stable structure of coordination between government bodies. We need well-organised marine and coastal monitoring, and that requires political will and resources. Also, many vessels mooring here come from other countries such as France or Croatia. This is why it’s important to harmonise legislation at Mediterranean level, so that all posidonia is protected equally, not just that of the Balearic Islands.

You’ve been involved in international networks on marine conservation. What role do they play?

They’re fundamental. In 2019, together with a colleague from the French Biodiversity Office, we founded the Mediterranean Posidonia Network. We started as two people at a meeting in Athens, and today there are 250 members from 15 countries. Experts, scientists, institutions and companies all share their experiences. We were recently in Tunisia, home to 40% of posidonia in the Mediterranean, working with countries such as Libya, Algeria and Egypt. A very powerful network has been created that allows us to learn from each other, but also to show that what we’re doing in the Balearic Islands, which is a great deal in many respects, is groundbreaking.