Why do some islands in the Vava'u Group shrink over time?

Many islands in the Vava'u Group are shrinking primarily because they lack the protective coral reefs that surround other Tongan islands, such as Tongatapu Island. Without this natural barrier, these islands are more directly exposed to the erosive power of the sea.1

Additionally, the islands experience significant natural erosion due to chemical and physical processes. Rainwater, which becomes acidic after reacting with carbon dioxide in vegetation, dissolves the coral and limestone rock that compose these islands, leading to the formation of caves. Furthermore, the constant action of ocean waves contributes to the creation of sheer cliffs and the gradual wearing away of the land.1