Beschreibung:
<p>Yap State in the Federated States of Micronesia consists of 16 islands distributed over a distance of nearly 1,000 km across the western Pacific Ocean. Four island types are present in Yap State: The main Yap Island group consists of four large and several smaller, high volcanic islands surrounded by a fringing reef. Ten of the islands are atolls which consist of an annular reef rim enclosing a central lagoon. Low-lying islets, composed mainly of reefal debris, are scattered on the upper surface of the atoll reef rim. There are four reef islands, which are low-lying coral islands developed on a small reef platform and devoid of a significant lagoon. The remaining island (Fais) is a high limestone island partially surrounded by a narrow fringing reef with the remainder of the island consisting of a cliffed coast. On the main Yap Islands, there are three critical coastal environments: mangrove forests, sand beaches, and coral reefs. Mangrove forests comprise about 10% of the total land area and have an alongshore distance of nearly 114 km. The mangrove area has been expanding throughout the Holocene, and will continue to expand in a landward direction as low-lying coastal land becomes intertidal. Shore erosion would probably be minimized due to mangrove protection. Sand beaches and associated coastal plains are limited in extent, occurring in exposed localities and comprising only about 0.25% (0.24 km²) of the total land area. However, they form important settlement sites and are critical to modern and traditional Yapese culture. Sand beaches are extremely vulnerable to accelerated erosion, and a landward shift of the shoreline profile during a rising sea level can be expected. Coral reefs surround the main Yap Islands and are a source of sediment for the beaches and adjacent coastal plains. Reef response to accelerated sea-level rise is probably one of expanded vertical growth and increased carbonate production as shallow substrates are submerged. The low-lying atolls and reef islands of Yap State will potentially suffer severe consequences of accelerated sea-level rise. Maximum elevation of these islands is around 7 m with an average elevation of 3-4 m above MSL. They are composed primarily of easily eroded unconsolidated reef debris.</p>