Eight years after the Balearic Islands introduced landmark legislation to safeguard Posidonia oceanica, one of the Mediterranean's most valuable marine ecosystems, environmental organisation Amics de la Terra says Ibiza's underwater seagrass meadows remain under significant pressure from illegal boat anchoring, marine pollution and climate change.

While the Balearic Posidonia Protection Decree (Decree 25/2018) has helped improve conservation efforts and reduce damage across the islands, the organisation warns that stronger action is still needed to address increasing boating activity, ageing wastewater infrastructure and the growing impact of warming seas.

Southwest Ibiza Remains One of the Most Vulnerable Areas

According to Amics de la Terra, Ibiza's southwest coastline continues to experience some of the highest levels of recreational boat anchoring in the Mediterranean, placing constant pressure on fragile Posidonia meadows.

The Balearic Posidonia Surveillance Service carries out more than 10,000 inspections each year, with around 10% of inspected vessels reportedly found to be anchored illegally or incorrectly over protected seagrass beds. Although boats are instructed to relocate and can face penalties, the organisation says damage has often already been done before inspectors arrive.

Pollution Continues to Affect Coastal Waters

Illegal anchoring is only one part of the problem.

Amics de la Terra also points to untreated wastewater discharges, chemical pollution, plastics, oil contamination and brine released by desalination plants as ongoing threats to Ibiza's marine environment.

The organisation argues that ageing wastewater treatment systems, combined with the intense pressure created by peak summer tourism, continue to affect water quality. It also links these issues to episodes of green, cloudy seawater and algae blooms that have appeared along several Ibiza beaches in recent years.

Rising Sea Temperatures Add Another Challenge

Climate change is becoming an increasingly serious concern for the future of Posidonia.

According to Amics de la Terra, sea temperatures exceeded 30°C in parts of the Balearic Islands during 2025, surpassing the approximately 28°C threshold that the organisation considers critical for the long-term health of the seagrass.

Marine heatwaves are widely recognised by scientists as one of the greatest threats to Mediterranean ecosystems because prolonged high temperatures weaken Posidonia's ability to recover from damage caused by anchoring and pollution. Recent monitoring around Ibiza has also recorded seawater temperatures above 30°C affecting the health of local meadows.

Why Posidonia Matters

Often referred to as the "lungs of the Mediterranean," Posidonia oceanica is far more than just seagrass.

The underwater meadows produce oxygen, absorb and store significant amounts of carbon, provide habitat for hundreds of marine species, protect Ibiza's coastline from erosion and help create the island's famous crystal-clear waters and white sandy beaches.

The extensive Posidonia meadows between Ibiza and Formentera have been recognised as a UNESCO World Heritage Site since 1999 because of their exceptional ecological importance.

Calls for Stronger Protection

Amics de la Terra is urging authorities to strengthen marine surveillance, invest in modern wastewater treatment facilities and expand protection across marine areas included in the Natura 2000 Network.

The organisation says that while legal protection has delivered important progress over the past eight years, safeguarding Ibiza's Posidonia will ultimately require tackling both local environmental pressures and the accelerating effects of climate change.