The Sundarbans Tiger Reserve, created in 1973, was the part of the then 24-Pargans Division. Subsequently the area comprising of the present tiger reserve was constituted as Reserve Forest in 1978. The total area of the Sunderbans is 9630 sq. km. out of which 4264 sq. km. bears mangrove forest. The area of the Reserve is 2585 sq. km. covering land area of 1600 sq. km. and water body over 985 sq. km.
Within this area 1330.12 sq. km. is designated as core area, which was subsequently declared as Sundarban National Park in 1984. An area of 124.40 sq. km. within the core area is preserved as primitive zone to act as gene pool.
Within the buffer zone, Sajnekhali Wildlife sanctuary was created in 1976 covering an area of 362.335 sq. km. Considering the importance of the biogeographic region of Bengalian River Forests and its unique biodiversity the National Park area of the Reserve was included in the list of World Heritage Sites in 1985. Whole Sundarbans area was declared as Biosphere Reserve in 1989.