Ibiza, biodiversité et culture

The oceanic Posidonia meadows are protected by the Ses Salines Natural Park, however the significant maritime traffic in the area, especially in summer, presents the main threat for the natural component of the World Heritage site. The area between Ibiza and Formentera, known as Es Freus, has high boat traffic. In addition, in summer, there is a strong presence of pleasure boats that anchor in the area. Although buoys have been installed to allow anchoring without damaging the meadows, the small number of buoys and the fact that they do not allow lengths greater than 35 m, which are very common today, does not solve the problem (Ramón-Cardona et al. 2021). Satellite imagery has shown that ships continue to anchor on the Posidonia despite this being prohibited (Ferrer, 2024). Ses Illetes, the area near the port of La Savina, and the island of S’Espalmador are the most problematic areas (Ramón-Cardona et al., 2021).

In 2021 the Balearic Environment Commission called on the State to “regulate and reduce” the berthing of cruise ships in the port of Ibiza and the traffic of regular boats between the Pitiusas in order to ensure the protection of the Natural Park of Ses Salines. The environmental body of the Autonomous Community has reported in favour of the Plan de Ordenación del Espacio Marítimo of the Levantine-Balearic coast that the central government is processing as long as it fulfils this, along with other conditions. In its report, which is not binding, the Balearic Environment Commission considers that, given the risk of fuel spills and other damage caused to the environment, actions should be coordinated between the State, the Autonomous Community and the local administrations of the island “aimed at reducing maritime frequencies between the Pitiusas”, a demand that the Consell de Formentera has also made to the Balearic Govern. Another request is that the central government “reduces” the berthing of regular line boats, shipping companies and cruise ships in the ports of Ibiza and La Savina. Thus, it is proposed that the Maritime Space Management Plan should organise and regulate the relevant activities and uses of the port areas according to “the potential of each area, as well as its load capacity and its environmental status”. With this, it is proposed to limit the number of cruise ships that can be found in a destination, their size or other measures to “minimise the impact of this activity” (Martos, 2021).

The environmental body of the Autonomous Community warns that, in the case of the Pitiusas, "the suitability of this maritime space in relation to maritime transport and activities related to leisure and boat tourism has already been exceeded". In fact, the plan being processed by the State points out that the demarcation of the Levantine-Balearic area shows "high densities of ships at several points", including "the route that connects Ibiza with Formentera". In addition, the data used are from 2016, when the Balearic Islands warned that since that year, at least until 2019, before the health crisis, "the annual evolution of the activity [of maritime traffic between the Pitiusas] has increased" (Martos, 2021).

In 2024 an image from the Sentinel satellite of the Copernicus program, recorded that between the ships that are in full navigation and those that remain anchored off the coast (small white dots can be seen, especially in front of ses Illetes de Formentera, s’Espalmador and ses Salines de Eivissa), the figure is around 400 boats. Although most of the anchored vessels appear to be on sandy ground, it is also apparent that many others do so on Posidonia (especially visible in ses Salines de Eivissa), despite this being totally prohibited and subject to heavy fines. In fact, these uncontrolled anchorages on the seagrass meadows are one of the main causes of their progressive disappearance. According to a study made public in December 2018 and prepared by the Natural Park’s management team, es Freus supports per year an average of 1,960 boat trips per day during the summer. Although this is the summer average, there are peaks of up to 2,494 transits (Ferrer, 2024).

That means that during that time of year there are no less than 82 to 104 ships per hour traveling through the strait. Of all these boats, 10% are regular traffic ferries, while the rest are recreational vessels of all sizes. Of these, only 8% were sailing vessels, while the rest were motorboats, according to the report, which analysed the traffic recorded that year and the previous year (Ferrer, 2024).

Turbulence and turbidity from ferries and boats negatively affects Posidonia. Underwater noise is also quite significant and proved through measurements to have negative impacts on the seagrass ecosystem. The extent of the cumulative impacts on the values of the site is being analysed. Beginning in 2018, five coastal boats patrol the Natural Park, informing the people on boats and yachts of the rules, including the interdiction to anchor on seagrass and dropping waste; however, they do not have the power to fine. Despite this, the total number of boats and yachts sailing through or visiting the site has not declined, although this action has resulted in a substantial reduction of the negative impacts these recreational activities have had in the site prior to 2018. However, this impact has been displaced to surrounding areas, including Talamanca (IUCN Consultation, 2020).

The most invasive macrophytes in the property are green algae Caulerpa racemosa, and red algae Lophocladia lallemandii, Acrothamnion preissii and Womersleyella setacea (Piazzi et al., 2001; Ballesteros and Cebrian, 2004; Cebrian and Ballesteros, 2010). Lophocladia lallemandii in particular has reportedly spread in past years, causing a direct negative impact on Posidonia oceanica habitats (Ballesteros et al., 2007). However, the impact of this species appears to have decreased, the reasons why are not known. Some experts think that it may be a transient effect (IUCN Consultation, 2020). A three year expansion of Batophora occindentalis has been observed in the coastal lagoon of Estany des Peix (Forteza et al., 2024).

Sewage input from recreational boats inside the area has been substantially reduced since 2018 in the site thanks to information by the coastal boat patrols. However, this has been displaced into the buffer zone and neighboring areas (IUCN Consultation, 2020). This impact has a cumulative effect with current eutrophication of coastal waters from urban wastewater and brine from desalination plants and climate change, enhancing phytoplankton growth, reducing water transparency and provoking macrophyte (including seagrass) decline (Sobrado et al., 2018).

Although reduction in tourist numbers is recommended to reduce pressure on Posidonia meadows (Sobrado & Palomares, 2025), among many other impacts, it appears that tourism continues to increase, although figures for tourists solely visiting the property were not available. However, for Ibiza and Formentera, in 9 months 3.3 million tourists visited the islands in 2023, 242,407 more than the same period in 2022 (Makepeace, 2023). In 2024, the numbers appear to have even increased even more (TTW, 2025). The beaches of Ses Salines and Es Cavellet are among the most heavily used of Ibiza (IUCN Consultation, 2020). The dune, beach and coastal ecosystems are deteriorating both in the terrestrial part of Ibiza and that of Formentera due to excessive tourist use. Signs to prevent people from entering the dunes have been insufficient. In some places, e.g. Cavallet beach, these impacts are exacerbated by (illegal) parking of motor vehicles. In several places, such as Formentera, the trend of removing surface materials to create small land-art type of sculptures has become a problem (IUCN Consultation, 2020). The international popularity of Ibiza has created a "halo effect" that has intensified the commercialization of the protected area through media and promotional events. Examples include the advertisement of mass events (Periódico de Ibiza, 2024) and the execution of commercial activities without proper authorization, such as renting the area for private events (Cadena SER, 2025), and unauthorized filming of a music video for a major international artist (Diario de Ibiza, 2024).

Marinas and other tourism infrastructure near the site (e.g. at Ibiza town) are adding to seagrass destruction, eutrophication and related disturbances. The urban plan of the Ibiza City municipality adopted in 1987 allowed for huge urban expansions, beyond water resources, despite that 85% of the municipal coast is already built (Murray, 2013). A new urban plan was approved in 2023 and should include significant growth reduction (Eivissa, 2023). However, the damage may already have been done, since the Balearic Islands as a whole have increased development in the first kilometre of coastline by 37.6%, mainly due to urban expansion and commercial activities related to tourism, with the consequent impacts on the environment (Vaquer-Sunyer et al., 2020).

The number of tourists and tourist accommodations has been increasing over time until 2018, with an increase of more than 16 million in 59 years. In 2019, it was slightly lower than the previous year, going from 16.56 million in 2018 to 16.44 million in 2019. This increase has been much more pronounced this century, as the number of tourists visiting the Balearic Islands has more than doubled. The number of legal tourist accommodations has continued to grow over time, reaching 607,522 in 2023. The number of tourist accommodations in holiday homes has increased since 2017, when it was legalized. By island, Formentera has the highest percentage, with 47% in 2021 and 2022; Ibiza has the lowest percentage, with 19.8% in 2022. The increase in both the number of tourist places and the number of tourists visiting the Balearic Islands has significant consequences for resource consumption and waste production (Vaquer-Sunyer et al. 2024).

Plastic pollution is becoming increasingly documented as a high threat to marine biodiversity (Ruiz-Orejón, 2018; GEN-GOB, 2024a; Martinez et al., 2024). Additionally, ingestion of microplastics by species as the invasive Callinectes sapidus threaten potential predators of this species (Compa et al., 2023).

Various effects of climate change on seagrass stands and ecosystems have already been documented (e.g. Marba and Duarte, 2010). Increased water temperature enhances the thermocline effect, increasing plankton density, reducing water transparency, creating cumulative impacts with water pollution to Posidonia seabeds, whilst favoring invasive alien macrophytes such as Caulerpa racemosa and Lophocladia lallemandii. The Oceanographic Centre of the Balears recently published a study showing that, if the current warming trend continues, the coastline of the islands would recede by 20 centimetres per year, meaning the loss of seven beaches in Ibiza and six in Formentera, while a good part of the rest would be reduced by half (Greenpeace, 2024). Another quantification of the future total water level and coastline retreat for 869 beaches across the Balearic Islands for the next decades as a function of greenhouse gases emission scenario shows that according to the most pessimistic scenario (RCP8.5) at the end of the century yields an averaged percentage of flooded area of 66% under mean conditions which increases up to 86% under extreme conditions. Moreover, 72 of the 869 beaches of the region would permanently disappear while 314 would be completely flooded during storm episodes (Agulles et al., 2021).

The increasing occurrence of Caretta caretta nesting in the area (GOIB, 2021), while perceived as a positive sign of ecological recovery, may generate new conservation challenges as potential increased management needs during the tourist season, and added pressure on dune systems.

Alien invasive ladder lnakes (Zamenis scalaris) threaten the Ibiza Wall Lizard Podarcis pityusensis (Montes et al., 2022; GEN-GOB, 2024b). There is an ongoing effort to trap invasive ladder snakes and prevent them for invading small islets (Picó et al., 2019; GOIB, 2025). Invasive feral cats and black rats threaten the Balearic Shearwater population breeding on Formentera (McMinn & Cooper, 2015). Invasive plant species are also present in the area, as Carpobrotus edulis and Kalanchoe × houghtonii (GOIB, 2021b; Serapio et al., 2023). The invasive blue crab, Callinectes sapidus, was also detected in the area in 2018 (Box et al., 2020).