SHORELINE DYNAMICS AND BREEDING COASTAL BIRDS IN THE MARANO AND GRADO BARRIER ISLANDS

Covering almost 12% of the world’s coasts, barrier islands are ideal habitat for many species of coastal birds. The functionality and benefits related to these coastal environments have recently been threatened by the reduction in sedimentary input, sea level rise, and human activities. Part of the Natura 2000 network, the system of sand banks and barrier islands of the Marano and Grado Lagoon (NE Italy) maintains a high degree of naturalness. Here, the Oystercatcher (Haematopus ostralegus), the Little tern (Sternula albifrons), and the Kentish plover (Charadrius alexandrinus) are the most distinctive bird nesting species of conservation concern. We examine the monitoring of target species during the nesting phase over a ten-year period (2013 to 2023) and look into the possible effect and/or constraint exerted by the morphodynamic setting of the nesting habitat. The analysis focuses on key geomorphological indicators, such as coastline advance or retreat, as well as variations in the island extent. The results indicate that the barrier system is self-sustaining despite a general rollover process. An external longshore sediment input is responsible for supplying a compensating longshore process that counteracts short-term, localised morphological changes such as spit progradation and washover development. In this morphodynamic context, the nesting population of Oystercatchers has grown over the years, while greater difficulties have been registered for the Little tern and the Kentish plover, whose breeding success has been more limited and is probably more constrained by the high dynamism and ephemeral characteristics of the barrier islands habitat. This underlines how, despite sharing the same nesting habitat, the response to different pressures could vary from species to species. Furthermore, our results allowed to provide a first set of management indications for species protection, based on the principles of adaptive management and maintenance of morphodynamic processes.