Mediterranean reflections in view of the Third United Nations Ocean Conference (UNOC3) (Nice 9-13 June 2025)
By Thierry Duchesne, Director of the Maritime Department of the FMES Institute
The French Mediterranean coastline, long seen as a space sacrificed to development and environmental neglect, today embodies the example of a possible watershed. Since the 1970s, when alarmist narratives predicted the death of marine ecosystems, major changes have taken place. Through a combination of strengthening scientific research at sea, structuring public policies, investments in infrastructure, territorial cooperation and citizen pressure, the catastrophic trajectory of the environment in the Mediterranean Sea has changed. This article, based on the debates held during the symposium “New challenges of environmental protection in the Mediterranean in the perspective of UNOC3” (April 18, 2025 – Marseille), offers an overview of the major dynamics behind this environmental recovery.
From failure to mobilization
At the turn of the 1970s, the environmental situation of the Mediterranean coastline was disastrous. Coastal waters had pollution levels such that many beaches were unsuitable for swimming. Floating waste, untreated effluents, oil residues, foul odors, and serious health risks were the norm in several urban or port areas. In addition, there was a climate of mistrust between authorities, scientists and users, each blaming the others for inaction.
It is against this background of crisis that the first dynamics of reconquest emerged. The development of knowledge tools, including cartographic and hydrological tools, has made it possible to better understand the origin of pollution. This strengthening of the scientific base has made it possible to implement more targeted and measurable policies. In addition, changing attitudes, with the emergence of the concept of “leaving a sea in a better state for future generations” and increasing public pressure, have played a leading role in the political will to address the issue of the coastline in ways other than as a simple adjustment variable.
Sanitation, the foundation of recovery
The construction and modernization of the sewage treatment plants have been the basis for improving water quality. Until the beginning of the 2010s, investments made it possible to compensate for the increase in the coastal population by ensuring minimal treatment of discharges. But only with the introduction of strict European standards, together with technical and financial support for local authorities, has the trend really reversed. The volume of pollution discharged at sea has begun to decrease, not only proportionally, but also in absolute terms.
Today, more than 94% of France’s coastal waters comply with EU environmental quality standards. This improvement is tangible every day in the seaside experience of users of coastal waters: swimming waters are safer and cleaner, effluents are better controlled, and some marine species return to areas where they had disappeared. This progress illustrates the power of an essential triad: knowledge, regulation, corrective action.
A changing territorial governance
Recognition of the link between sea and continent has been gradually but firmly established. Unlike rivers, whose watershed operation is intuitively understood, the sea has long been perceived as an indeterminate downstream area, autonomous and disconnected from the interior. This vision has been shattered as diffuse pollution and continental inputs have been better identified.
Territorial policies then integrated the coastal issue into a systemic logic. Cooperation between local authorities, the water agency, state services and civil society actors has been strengthened. Territorial planning has evolved to integrate environmental imperatives. The application of the Littoral Act has considerably reduced the uncontrolled urban development and the destruction of the shallow coastal habitats. The creation of the Coastal Conservatory in 1975 has been an accelerator of coastal protection with today more than 2000 km of protected coastline. Now, more than 16% of the coast of the PACA region belongs to the Conservatory and even 24% for Corsica. These measures have led to a sharp slowdown in concreting and a better integration of coastal areas in their hinterlands.
Marine protected areas: a tool to be structured
The strong development of marine protected areas (MPAs) has been a major feature of French maritime areas since the early 2000s. More than 85% of France’s Mediterranean coastline is now covered by at least one protective device. However, this density alone does not guarantee real efficiency. Indeed, the coexistence of many categories of MPAs (11 different statutes) – with varying objectives, statutes and levels of constraint – undermines their clarity and, at times, their legitimacy.
The development of local governance around MPAs has nevertheless encouraged dialog between stakeholders. These spaces have become laboratories for consultation, where fishermen, scientists, associations and communities can co-construct rules. Some MPAs with higher protection status have demonstrated measurable positive effects on fish stocks, marine habitats and even the local economy. However, the lack of human resources, bureaucratic red tape, the weakness of controls and the absence of no-take zones on many sites (only 0.9% of the areas are actually protected) still hinder their potential. It is becoming essential to simplify the statutes, strengthen management capacities and ensure real environmental protection where it is truly necessary. It should be recalled, however, that a healthy sea in balance with coastal and marine activities goes beyond marine areas to be an objective applicable to all coastal marine regions. This is, moreover, the very essence of European directives.
Regulation and innovation against marine pollution
Pollution from maritime traffic – hydrocarbons, solid waste, bilge water – has been greatly reduced since the late 1990s. International regulations, in particular thanks to the MARPOL1 Convention, now prohibit all discharges that pose a threat to the environment. Above all, however, France has developed effective surveillance tools, combining air, maritime and satellite resources implemented by all the administrations involved at sea. Thanks to a rapid detection of pollution, a centralization of suspicions of discharge by the Mediterranean CROSS and the firm resolve of the Maritime Prefect, in coordination with the Public Prosecutor, to redirect any ship caught carrying out a voluntary pollution, discharges have become extremely rare. The last significant release was in June 2021, when a very large hydrocarbon slick was discovered in the Corsica Canal. Numerous means of combating pollution have been sent from the mainland of Corsica and have made it possible to treat it at sea without it affecting the Corsican coasts. The ecological impact on the coasts could thus be very marginal… Deterrence also requires the heavy penalties that are now imposed by the specialized courts, the JULIS (specialized coastal courts) based in Marseille for the Mediterranean region. However, there are still areas for improvement, particularly in the cleanup of polluted areas on the coast, where the consideration of ecological data is often neglected.
On the other hand, chronic pollution of low magnitude and low impact, especially from recreational boating, remains difficult to control and calls for better accountability of users.
Posidonia, an indicator of this reconquest
The Posidonia herbarium is a symbol of the Mediterranean, a vital biodiversity habitat, a natural carbon sink, and a shield against erosion (79,000 hectares of Posidonia in the French Mediterranean). Despite an arsenal of legal protections (law, European directives, international conventions), this ecosystem was shrinking annually. The main cause of these violations is related to the increased anchorage of ships, especially the many large yachts, which anchor in this fragile ecosystem. Hundreds of hectares have been destroyed in a few years and irreversibly on a human scale. Over the past century, Posidonia seagrass losses are estimated at 10%, rising to 30% in just eight years in certain areas such as the Gulf of Saint-Tropez, the Cap d’Antibes or the Bay of Calvi. Previously, this habitat was not affected by marine traffic of this nature (yacht anchorages are not those of the merchant navy) and with this intensity. Between 2010 and 2018, there was a 449% increase in anchorages on the Mediterranean coast. In 2024, the total number of registered anchorages was 63,000 recreational vessels, of which about one third were vessels over 24 meters.
In response to this threat, strong measures have been taken. Anchoring bans have been introduced by the Mediterranean Sea Prefect for large vessels (over 24 meters) on seagrass beds, accompanied by a reinforced control system. At the same time, ecological buoys have been installed in certain areas allowing vessels to stop without anchoring.
Geolocation systems such as @Donia system have guided boaters to anchorages free of posidonia. These actions, undertaken as early as 2019, have borne fruit: the areas of herbaria affected, between 2020 and 2021, have decreased by 80% in certain sectors and signs of natural regeneration are already observed.
Efforts are also being made in the area of active restoration. Cutting and transplantation techniques are being tested, although the slow growth of posidonia limits its effectiveness. This dynamic of protection and this coherence of measures is a successful example of convergence between regulations, technical innovation, user awareness and scientific monitoring.
Conclusion
The French Mediterranean coastline and maritime areas have been able, in the space of a few decades, to reverse a seemingly irreversible trajectory of degradation. This shift did not happen overnight, nor without tensions, but it shows that collective mobilization grounded in knowledge, regulation, investment and stakeholder engagemen can produce tangible results. This partial success should not mask the persistent challenges: climate change, demographic pressure, artificialization, fragmentation of governance. The Mediterranean Sea is alive, but fragile. Today, it calls for ever greater vigilance, an ambitious adaptation strategy and broader solidarity between territories that must be sustainable.
