Towards sustainable management of the littoral zone for conserving the integrity of Posidonia meadows and the beach and dune systems in Epanomi, Metropolitan Unit of Thessaloniki, Region of Central Macedonia, Greece

The Region of Central Macedonia, Consortis and the Municipality of Thermaikos are working towards setting a basis for the sustainable management of the municipality’s littoral zone

Posidonia meadows, sandy beaches along with Posidonia banquettes, and coastal dunes form unique multifunctional ecosystems, which are very important for the Mediterranean coasts. Unfortunately, the integrity of these ecosystems is subjected to several human activities/threats, while the value of Posidonia banquettes is often underrated even though they play a prominent role for biodiversity conservation but also for protecting coastal beaches from erosion.

Within the framework of the POSBEMED2 project, the Region of Central Macedonia, Consortis and the municipality of Thermaikos are working towards setting a basis for the sustainable management of the municipality’s littoral zone within protected areas and their vicinity.

The chosen testing site (Epanomi/Potamos beach) is located in the southwestern part of the Municipal Unit of Epanomi along the Thermaikos Gulf in Northern Greece, approximately 25 kilometers from the city of Thessaloniki.

The site is a complex system, combining marine and terrestrial ecosystems such as Posidonia oceanica meadows, diverse dunes, and wetland habitat types. The site, as well as the broader area, is of very high ecological significance since it harbours several plant and animal species, including a high number of birds, most of which are under protected status by EU and International legislation. The broader area is part of the Natura 2000 network of protected areas and consists of a Site of Community Importance "Limnothalassa Epanomis & Thalassia Paraktia Zoni - GR1220012" and a Special Protection Area "Limnothalassa Epanomis - GR1220011".

In the littoral zone of Epanomi the biomass gathers to wedge-shaped structures, which range from a few centimeters up to 1.5 meters thickness, forming characteristic configurations known as banquettes. Banquettes contribute to the construction of dunes and form a morphological, functional, and ecological complex, the “beach-dune complex”. This complex inhabits an extraordinary range of biological diversity and provides significant ecosystem services.

As in many Mediterranean coastal regions, Epanomi beach is an important destination for tourism. Taking into consideration that the area is close to the city of Thessaloniki, which has 1.5 million inhabitants, human pressure is high during the entire year, but especially during the summer months. Important to note here is that the tourist/leisure activities in the area and the access into habitats (e.g. dunes) is uncontrolled. Following the trend of many Mediterranean coastal cities of keeping a clean Posidonia-free picture of beaches, several parts along the coast of Epanomi are cleaned on a regular basis.

The beach "cleaning" operations (if not avoidable) have to be carried out with significant caution and special equipment. When carried out by heavy machines, which remove the "litter biomass" along with the sediment, the integrity of the littoral zone becomes endangered while the beach morphology is gradually altered, and the sand may be washed away.

In order to protect the site’s great ecological value, maintain the Posidonia meadows and beach-dune complex integrity and furthermore secure the delivery of its multiple ecosystem services, a sustainable management scheme of the littoral zone is essential.

The development of the management scheme for Epanomi depends first and foremost on specific evaluations and measurements. Thus, a variety of complementary methods, including field and laboratory measurements as well as modern surveying and mapping techniques to collect data for high-resolution mapping were employed. Significant targets included:

  • The evaluation of Posidonia oceanica meadows by underwater measurements and analysis of collected samples
  • The evaluation of banquettes by measuring the thickness of banquettes, calculating biomass accumulation, and analysing collected samples
  • The estimation of vulnerability to erosion by analysis of the beach sediments
  • The survey, mapping and data collection of the coastal zone encompassing techniques such as high accuracy aerial survey using UAV, high accuracy land survey using GNSS, high accuracy sonar survey of the shallow water zone up to a depth of 20 m using GNSS.

Remote sensing techniques, such as optical images analysis, were also used to support the monitoring needs of the posidonia meadows as well as of the properties of the water ecosystem. Producing such thematic maps from Earth Observation data is a multistep process. First, a preprocessing phase to correct satellite images was applied followed by classification phases to improve the accuracy of the results.

Finally, the area was investigated for subsidence/uplift phenomena in comparison with the presence of Posidonia oceanica. Data processing included methods such geodata base creation, analysis through Digital Elevation Models and Interferometry analysis (InSAR).

On the whole, the results showed that if the "business as usual" continues (i.e. cleaning of beaches, removal of banquettes, uncontrolled touristic/leisure activities) then this will result into a dramatic impoverishment of the biodiversity, the degradation of habitats but also the loss of the beaches due to storms being accelerated by climate change in future. The preservation of this unique area and the ecosystem services it delivers, presupposes the protection and conservation of the banquettes – dunes complex. To save the seaside tourism industry, the financial resources of local authorities and coastal Mediterranean biodiversity, it is significant to invest in public awareness and to promote “ecological-Posidonia-compatible" beaches.