The deposition of Posidonia oceanica leaves on the sandy beaches of the Calabrian region could be one of the most important defence mechanisms against erosion processes. The management of Posidonia oceanica leaf litter in Italy has been realised through the mechanical removal and transport in dumping areas of the beach-cast material. This solution, apparently simple and fast, produces a net loss of sediments from sandy beaches and, therefore, a deficit in the sedimentary budget of the coastline, leading the coastal system to possible shore erosions. Instead, it could be better to keep these vegetable deposits in place to warrant a positive sedimentary budget and to increase the tourist value of regional beaches, improving coastal tourism in seaside resorts with opportunities for bathing.

Worldwide, plastic debris is becoming a great environmental problem, with potentially negative effects also on human health, although currently the topic is highly debated in the scientific community. In the basin, microplastics come mainly from three coastal regions, namely Egypt, Turkey and Italy, in decreasing order. Today, the knowledge about the possible interactions of microplastics in the biotic system is unclear and huge efforts are required to discover their effects on human health. Therefore, it is necessary to reduce the production and use of plastics by investing money in research planning and strengthening any kind of human efforts to solve this new kind of marine pollution.

In the Mediterranean Sea, two critical issues affect marine benthic biocenosis: sedimentation and the increasing trend in marine biodiversity loss. These processes are very marked along the western side of the Calabrian coastline, where siltation is one of the main reasons for the regression of Posidonia beds in the regional coastal waters. This study investigates the relationships between the geomorphological features of the debris source areas, represented by fluvial basins, and the distribution of Posidonia meadows. So, a concise geomorphological study of the Tyrrhenian fluvial basins with an area greater than 200 km² was carried out, and we correlated the results with the mapping of the meadows in Calabria’s Tyrrhenian waters. Furthermore, to assess the increased level of burial in a Posidonia oceanica meadow and its health state over time, a program of Posidonia monitoring was undertaken between 2000 and 2010 in a test area located in the Marine Regional Park of Isca (Calabria, Southern Italy). The results of this survey highlighted that, at the beginning of the study period, the silting rate of 4–5 cm/year saw the meadow suffer a reduction in its photosynthetic ratio with a mortality rate of 50%. The siltation rate reached 12 cm/year in 2010, and the meadow began to disappear. Therefore, marine pollution via sedimentation represents a serious factor in the regression of Posidonia oceanica meadows and enhances the risk of a gradual loss of marine biodiversity.

Climate changes are affecting the fate of Posidonia oceanica meadows. Actually, the Mediterranean Sea is threatened by abiotic, biotic and climate changes coupled with human pressures regarding coastal regions. In this way, Posidonia oceanica is able to counteract the effects of climate changes through the high thermotolerance of the species, range shift processes of the meadows and variations in the community composition of this valuable marine ecosystem. Anyway, the power of acclimatization to temperature shifts and the adaptative capacity of Posidonia oceanica meadows against human pressures let to suggest a positive trend in the long evolutionary pathway of the species.