Erosion and worsening water quality threaten the islands' beaches

The 2022 Balearic Sea Report (www.informemarbalear.org) — a collaborative project in which all the islands' marine research institutions together with public and private entities participate by sharing their data — has compiled updated information on the state of the islands’ beaches. Here we mention some of the most relevant conclusions of the report.

A thorough 10-year study of shoreline beach evolution revealed that 20% of Mallorca and Formentera beaches and 10% of Menorca and Ibiza beaches show a retreating shoreline. Several scientific articles argue that urban beaches suffer greater erosion and recover less well from storms. Examples of these beaches are S’Arenal, Cala Millor, Cala Blanca, and Cala en Porter.

Construction elements, such as ports located in S’Arenal and Sa Ràpita, produce more sedimentation in areas close to the ports and more erosion in areas farther away, thus modifying the natural sedimentation patterns of each beach. Es Trenc shows a greater retreat in areas with the highest user traffic (e.g. close to parking). Cala Millor regeneration efforts for tourism and recreational purposes have resulted in high shoreline fluctuations since the beach is trying to find its sedimentary balance. Cala Deià shows regression derived from a higher wave intensification. The Menorcan beaches that have shown a higher erosion throughout the years are Cala Blanca, Llevant de Son Saura, Cala en Porter, and Sa Caleta.

The number of users and recreational boats anchored on Menorca’s beaches is also increasing. Since 2010, the average load supported by Menorca's beaches has been above the optimum limit (> 100% load capacity). In 2021, Menorca received 15% fewer tourists than in 2019 (pre-pandemic). Even so, the number of beach users continues to increase. The beaches with the least available surface area per bather (< 3 m2/user) are urban, unspoilt beaches with some kind of service: Binidalí, Cala Mitjana, Macarella, Tirant-Platges de Fornells, Sant Adeodat, and Son Xoriguer.

The highest number of boats at anchor on Menorca's beaches was also registered in 2021. Recreational boaters prefer to anchor on undeveloped beaches rather than on urban beaches. The highest nautical loads on the same day in 2021 was at La Vall-Es Bot and Es Tancats (141 boats), Son Saura-Bellavista (82), Santandria (82), and Macarella-Macarelleta (72).

Despite erosion and beach use, another important threat to consider is the faecal bacterial contamination (E. coli) of bathing waters. With every passing year, the quality of bathing water decreases reaching the lowest number of excellent-quality zones in 2021. Ibiza showed worse quality in 2021 with 50% of its bathing zones being less-than-excellent. Also in 2021, bathing was prohibited in all the islands due to bacterial contamination 28% more than in 2020.

To establish adequate beach management, it is necessary to continue monitoring the shoreline evolution of the islands’ beaches and to tackle erosion with long-term environmentally friendly solutions. To date, we only have data on beach use from Menorca and thus to manage and control beach carrying capacity more surveys of the remaining islands are needed.

The IMB collaborative project will continue gathering the best available information on the Balearic Sea and more updated content will be published on the website throughout the year.