Terraces of the Lebanese coast : evolution and recovery assessment

Abstract

In Lebanon, like other parts of the world, urbanization and coastal development are leading to a degradation of natural ecosystems and the diminishing of their ecosystem services. The effects of such development on vermetid platforms of the Mediterranean Sea, which is a hotspot for biodiversity, are not well studied. This master thesis aims to assess the evolution of the state of vermetid platforms in Lebanon over five decades through the analysis of relevant satellite and aerial imagery. It also aims to assess the impact of installed coastal defenses on the vermetid platforms of the Lebanese coast through observing their consequences on the density of Demdropoma petraeum and the species richness of macroalgae. The loss of vermetid platforms in Lebanon from 1962 through 2010 has been estimated at 812,504 m2 . During this period, the Caza of El Metn of the governorate of Mount Lebanon lost all its vermetid platforms. Monthly site visits were conducted over eleven months to assess the biodiversity recovery after human disturbance at Berbara and measure D.petraeum density and macroalgae species richness. Six transects were deployed, three of which at a disturbed intertidal zone where tetrapods were installed to serve as coastal defenses and the other three served as the control. It was determined that even after 5 years of the deployment of the tetrapods, biodiversity did not recover on the platform behind these structures and that macroalgae richness was significantly reduced, with complete annihilation of crustose coralline algae that serve as nurseries for Dendropoma larvae. Causal relations were not derived due to the complexity of the interactions involved. An ecosystem-focused engineering intervention to coastal defenses that can promote both the safety of marine life and people is wanting.