Environmental impact of development in the Sundarbans, is the study of environmental impact on Sundarban, the largest single tract mangrove forest. It consist of a geographical area of 9,629 square kilometres (3,718 sq mi), including 4,185 square kilometres (1,616 sq mi) of reserve forest land, and is a natural region located partly in southern Bangladesh and partly in the Indian state of West Bengal. It is ecologically a southern part of the Gangetic delta between the Hooghly river in India on the west and the Meghna river in Bangladesh on the east and is bounded by the Ganga-Padma, the Padma-Meghna on the north and by the Bay of Bengal on the south. The area that is not reserve forest land is inhabited by human settlements with a total population around 4 million (2003).