Diversity of angiospermic flora of West Bengal, India.

Abstract

Abstract West Bengal, 87,616 km2 in size, is the 13th-largest state in India, situated at 21°10′ to 27°35′N latitude and 85°50′ to 89°52′E longitude. For administration purposes, the state is divided into 20 districts comprising more than 400 blocks and 4300 villages. Forests of West Bengal state can be categorized broadly in to six major types. Total recorded forest land in the state is 11,879 km2, which constitutes 13.38% of the geographical area of the state. Of the 11,879 km2 forested area, 7054 km2 is Reserve Forest, 3772 km2 is Protected Forest and 1053 km2 is Unclassified Forest. Floristic composition of the state is still unknown to us and the preparation of information about the flora of the state is a long-time demand. In the present study, an attempt has been made to study the flora of the state, which reveals that the state possesses 4493 taxa of Angiosperms under 1578 genera belonging to 232 families. West Bengal has a wetland area of about 3,44,527 ha: 22 natural wetlands and one man-made cover more than 100 hectares of area. Besides these, there are about 57,000 small ponds with individual land area of less than 2.25 ha. This huge aquatic land area possesses 770 taxa of aquatic plants which belong to 456 genera under 159 families. There are 35 species belonging to 34 genera under 22 families, which are confined to the political boundary of West Bengal and regarded as the endemic plants of the state. Beside these, there are another 25 species of Angiosperm belonging to 22 genera under 13 families, which are endemic to West Bengal and are also found in other Indian states. In total, the state West Bengal contains 57 species of endemic plants belonging to 53 genera under 30 families. In the present study, after a critical perusal of the literature it has been observed that the state possesses 489 exotic taxa, which is 11.03% of the total floristic element of the state, and they belong to 18 different floristic regions of the world. The flora of West Bengal state are under immense pressure due to several biotic and abiotic factors, as a result of which the floristic diversity of the state leads towards many species being threatened with extinction. The flora of the Darjeeling district, part of the eastern Himalayan Hotspots region, face destruction due to tourist activities and increasing need for land development, for establishment of tea gardens, for industry, etc.; this has led to the absence of several floristic elements from the list of the state flora. In this connection, Aldrovanda vesiculosa is noteworthy. Different ex-situ and in-situ conservation strategies have been considered at government level to protect the flora of the state. As of 2007, there are five national parks in the state, 18 wild life sanctuaries, two biosphere reserves and one UNESCO World Heritage site, which play a part in the conservation process of the state flora and fauna. Beside these, there is one Ramsar site (wetland of international importance: East Calcutta Wet Land) which works for conservation of aquatic flora and fauna.