Eight years after the Balearic Islands introduced landmark legislation to protect Posidonia oceanica, one of the Mediterranean’s most valuable marine ecosystems, environmental organisation Amics de la Terra says the seagrass meadows surrounding Ibiza and Formentera remain under serious pressure from boat anchoring, marine pollution and rising sea temperatures.
The group acknowledges that the Balearic Posidonia Protection Decree (Decree 25/2018) has delivered significant progress in conserving and restoring the underwater meadows. However, it argues that existing measures will not be enough unless authorities tackle the island’s growing boating activity, improve wastewater treatment infrastructure and address the increasing impact of climate change in the Mediterranean.
Southwest Ibiza Remains a Critical Hotspot
While official monitoring indicates that Posidonia meadows across the Balearic Islands have remained relatively stable in recent years, Amics de la Terra warns that conditions around Ibiza, particularly along the southwest coastline, continue to be deeply concerning.
According to the organisation, Ibiza experiences one of the highest levels of recreational boat anchoring in the Mediterranean, placing constant pressure on fragile underwater habitats.
The marine surveillance service reportedly carries out more than 10,000 inspections every year, with approximately 10% of inspected vessels found to be anchored illegally or incorrectly over protected Posidonia beds.
Although authorities require offending boats to relocate and may issue penalties, the environmental group stresses that damage to the seagrass has often already occurred by the time inspectors intervene.
Wastewater Pollution and Tourism Pressure Add to the Problem
Beyond anchoring, untreated wastewater discharges, chemical pollution, plastic waste, oil contamination and brine released by desalination plants continue to threaten Ibiza’s coastal waters.
Amics de la Terra links these environmental pressures to ageing wastewater infrastructure and a tourism model that exceeds the island’s environmental carrying capacity, particularly during the busy summer season.
The organisation also believes insufficient wastewater treatment contributes to episodes of green, cloudy coastal waters and algae blooms, phenomena that have affected several beaches in recent summers and raised concerns over both marine biodiversity and bathing water quality.
Climate Change Is Becoming an Increasingly Serious Threat
The organisation identifies rising sea temperatures as one of the greatest long-term dangers facing Posidonia oceanica.
According to Amics de la Terra, sea temperatures exceeded 30°C in some areas during 2025, surpassing the 28°C survival threshold that the group considers critical for the health of the seagrass.
Scientists widely regard prolonged marine heatwaves as one of the most significant threats to Mediterranean ecosystems, reducing the resilience of Posidonia meadows and weakening their ability to recover from other human impacts.
A Vital Ecosystem for Ibiza’s Coastline
The organisation emphasises that Posidonia oceanica plays a fundamental role in maintaining Ibiza’s marine environment. The underwater meadows produce oxygen, store carbon, provide habitat for hundreds of marine species, help create the island’s famous white-sand beaches, and protect the coastline from erosion.
The extensive Posidonia meadows between Ibiza and Formentera have also been recognised as a UNESCO World Heritage Site since 1999 because of their exceptional ecological importance.
Amics de la Terra is calling for stronger marine surveillance across Ibiza’s coastline, significant investment in modern wastewater treatment systems, and enhanced protection for marine areas included in the Natura 2000 Network.
The organisation concludes that without stronger environmental policies addressing both human activity and climate change, legal protection alone will not be enough to secure the future of Ibiza’s Posidonia meadows.
