Delta Kayan Sembakung in Tarakan, North Kalimantan, Indonesia, is actually a cluster of mangrove vegetation that serves as a natural coastal fortress. A delta is a sedimentary landform found at river mouths in open seas, along beaches, or near lakes, formed as a result of reduced river flow when entering the sea.

However, in the 1990s, people began cutting down entire mangrove trees to create ponds for shrimp farming. Nearly 70,000 hectares of mangrove forest have been lost. As a result, the area now faces serious problems: the mangrove vegetation has disappeared, leading to coastal abrasion, drought, and barren land.