Indian Journal of Geo-Marine Sciences Vol. 42 (3), June 2013, pp. 331-342 Vegetation cover change analysis from multi-temporal satellite data in Jharkhali Island, Sundarbans, India 1 Sudip Manna*, 2 Partho Protim Mondal, 3 Anirban Mukhopadhyay, 4 Anirban Akhand, 5 Sugata Hazra & 6 Debashis Mitra 1, 3, 4 & 5: School of Oceanographic Studies, Jadavpur University, Jadavpur, Kolkata-700 032, India. 2 & 6: Indian Institute of Remote Sensing, (Indian Space Research Organization), Government of India, 4 Kalidas Road, Dehradun-248001, India. [E-mail: [email protected] , [email protected]] (Received 12 September 2011; revised 25 April 2012) Present study intends to quantify change of natural vegetation cover (mainly of mangrove forest) in Sundarbans Island between the time span of 2004-2010, when sustained efforts of a forestation and conservation has been in vogue. Vegetation indices like Normalized Difference Vegetation Index (NDVI), Global Environmental Monitoring Index (GEMI), Optimized Soil Adjusted Vegetation Index (OSAVI) and Transformed Difference Vegetation Index (TDVI) have been used to decipher the measure of vegetation cover in this island and its changes during the period. Radiometric normalization technique is used to nullify various imaging condition anomalies while comparing multi-temporal data for change detection analysis. TDVI has been found to be more effective in vegetation cover change detection in such deltaic environment. Present study shows an overall net increase of vegetation cover in the island as a result of sustained conservation and plantation efforts. [Key words: Vegetation, Conservation, Sundarbans, Mangrove, Spatiotemporal] Introduction Jharkhali being part of Sundarban group of islands (Delta of Ganges) is undergoing continuous changes. Indian part of Sundarbans, the largest Mangrove Forest on earth with an area of 9,630 km 2 , lies between 21°32′ –22°40′ N and 88°05′ –89°00′ E. 1 It hosts a wide and diverse range of flora and fauna. The Island is dominated by mangroves at periphery and also in the creeks with regular tidal influxes; mostly comprised of Aveccenia sp., Aegiceras sp., Aegialites sp., Bruguiera sp. etc. Along with mangroves, various back mangroves and xerophytes e.g. Exoecaria sp., Thespesia populnia etc. cover the vegetated area. Jharkhali island, previously part of the Namkhana Reserve Forest, is presently habited by fishermen and farmers. A strong population of 1, 28,802 2 in the year 2001 might have increased to 1, 58,092 by the year 2011 in Jharkhali. Anthropogenic impact caused by incessantly increasing population might caused around 16 km 2 mangrove forest deforestation 3 , for the purpose of settlement, agriculture and construction of bheries (shallow water bodies for brackish water aquaculture). In spite of a significant reduction in land area (around 86 km 2 ) in Sundarban island system during the past three decades 4 the island Jharkhali remained quite immune to coastal erosion, being 50 km inland from the southern sea front and protected from all sides by other land masses. Sustained conservation effort was taken at both government and community level in the form of wide-spread plantation, reclamation of land by natural succession and sincere effort to stop further degradation. There has been a reverse trend in Jharkhali Island regarding declining forest cover during the time period of 2008-2010 where the mangrove area increased by 265 ha by plantation in and around the island, and in the Indian part of Sundarbans 1610 ha of mangroves were planted at 70 locations during 2007-2010. 5 Though being young plantations the increase doesn’t contributes much to vegetation cover. Also an increase of 16 km 2 of mangrove cover in entire West Bengal during 2005–2007 is reported by Forest Survey of India 6 . Our present study is aimed at capturing that conservation effort in terms of increase in natural vegetation cover through multi-temporal change detection study. Under the present circumstances continuous spatiotemporal monitoring of the forest cover becomes a critically important element for —————— * Corresponding author: Phone and fax no. 033-24146242
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Indian Journal of Geo-Marine Sciences Vol. 42 (3), June 2013, pp. 331-342
Vegetation cover change analysis from multi-temporal satellite data in Jharkhali
1, 3, 4 & 5: School of Oceanographic Studies, Jadavpur University, Jadavpur, Kolkata-700 032, India. 2 & 6: Indian Institute of Remote Sensing, (Indian Space Research Organization),
Government of India, 4 Kalidas Road, Dehradun-248001, India.
(Received 12 September 2011; revised 25 April 2012)
Present study intends to quantify change of natural vegetation cover (mainly of mangrove forest) in Sundarbans Island between the time span of 2004-2010, when sustained efforts of a forestation and conservation has been in vogue. Vegetation indices like Normalized Difference Vegetation Index (NDVI), Global Environmental Monitoring Index (GEMI), Optimized
Soil Adjusted Vegetation Index (OSAVI) and Transformed Difference Vegetation Index (TDVI) have been used to decipher the measure of vegetation cover in this island and its changes during the period. Radiometric normalization technique is used to nullify various imaging condition anomalies while comparing multi-temporal data for change detection analysis. TDVI has been found to be more effective in vegetation cover change detection in such deltaic environment. Present study shows an overall net increase of vegetation cover in the island as a result of sustained conservation and plantation efforts.
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