ISLANDS BEHIND ISLANDS: A GLOBAL VIEW OF FETCH LIMITED BARRIER ISLANDS

There are more than 15,000 barrier islands in fetch limited nearshore marine environments around the world. About half of this number is actively evolving (eroding, accreting, migrating) in response to modern oceanographic processes and are the subject of this study. The remaining half are inactive islands enclosed by salt marsh or mangroves. Fetch limited barrier islands (FLBIs) interact closely with marshes, often controlling their location and growth patterns and in turn marshes do the same for islands. They are shorter than ocean barriers (average 1 km) but evolve in similar fashion except that overwash is almost always the dominant process and dune building is usually unimportant. More than 70% of FLBI's are found on trailing edge coasts where conditions are favorable for formation of sheltered waters in a time of rising sea level. Active fetch limited barrier islands are found in estuaries and bays (Chesapeake Bay, USA), behind ocean barriers (Pamlico Sound, USA), adjacent to inlets (Tapora Bank, New Zealand), rimming deltas (Menderes River, Turkey), eroding thermokarst (Yensei Bay, Russia) and glacial outwash fans (Canal Baker, Chile). The largest number of islands are in Laguna Madre, Mexico (596) followed by Obskaya Guba, Russia (405), Spencer Gulf, Australia (340), Shark Bay, Australia (338) and Chesapeake Bay, USA (218). Sheltered barriers are becoming the next frontier of development as available property on ocean barriers becomes a rarity.