Covering approximately 10,000 km2 the Sundarbans in the Northern Bay of Bengal is the largest contiguous mangrove forest on earth. Mangroves forests are highly productive and diverse ecosystems, providing a wide range of direct ecosystem services for resident populations. In addition, mangroves function as a buffer against frequently occurring cyclones; helping to protect local settlements including the two most populous cities of the world, Kolkata and Dhaka, against their worst effects. While large tracts of the Indian Sundarbans were cleared, drained and reclaimed for cultivation during the British colonial era, the remaining parts have been under various protection regimes since the 1970s, primarily to protect the remaining population of Bengal tigers (Panthera tigris ssp. tigris). In view of the importance of such forests, now severely threatened worldwide, we trace the areal change that the Indian Sundarbans have undergone over the last two-and-a-half centuries. We apply a multi-temporal and multi-scale approach based on historical maps and remote sensing data to detect changes in mangrove cover. While the mangroves’ areal extent has not changed much in the recent past, forest health and structure have. These changes result from direct human interference, upstream development, extreme weather events and the slow onset of climate change effects. Moreover, we consider the role of different management strategies affecting mangrove conservation and their intersection with local livelihoods.

The Indian Sundarban Mangrove Forests: History, Utilization, Conservation Strategies and Local Perception

Sea-level changes — The last 20 000 years

Rising sea levels and the increasing intensity of storm surges and tropical cyclones due to climate change and the resulting dynamic shifts in shoreline positions have dramatically increased the exposure risk and vulnerability of local communities inhabiting the ecologically sensitive deltaic tracts of the Sunderbans in India. The impacts arising from such hazard events on this fragile ecosystem need to be gauged to ameliorate the lives and livelihoods of these residents. This article examines the spatial distribution of vulnerability to coastal hazards within the Sundarban Biosphere Reserve (SBR) in India. For this, we have utilized several structural and process variables, which were integrated to construct a coastal vulnerability index (CVI), using the square root equation. The coastlines of the islands located within the SBR were overlain by 543 grids, each of 2 × 2 km dimension, to assign the risk rank for each considered variable. This revealed that of the total shoreline length (754 km), nearly one-fourth was very highly vulnerable, followed by highly vulnerable (27.8%), moderately vulnerable (27.9%) and low vulnerability (18.8%). Of the total islands located in these grids (27), the coastline of eleven islands was found to have very high vulnerability, five experienced high vulnerability, eight recorded moderate vulnerability while only three had low vulnerability status. The ambient geomorphological characteristics, coastal area slope, the rate of shoreline change and sea level rise were significant variables that accorded high and very high vulnerability to the islands. The CVI helped in identifying islands that require immediate attention for lessening the impact of climate change induced hazards in the SBR and also aided the assessment of the physical and coastal vulnerability conditions of these islands. This approach can be effectively utilized for assessing coastal vulnerability and for creating a holistic approach towards coastal conservation and management.

Assessing coastal island vulnerability in the Sundarban Biosphere Reserve, India, using geospatial technology

Dissolved trace elements in Hooghly (Ganges) River Estuary, India: Risk assessment and implications for management.

Shoreline changes and its impact on the mangrove ecosystems of some islands of Indian Sundarbans, North-East coast of India

Trends of annual sea level records of four tidal observatories of the Hugli estuary—Sagar, Gangra, Haldia, and Diamond Harbour—are analysed from the records of Permanent Service for Mean Sea Level (PSMSL). The rates of sea level changes for the stations are found to be –3.82, +0.89, +2.43 and +4.85 mm yr respectively, connoting a significant positive relation between landward distances of the stations and the rates of sea level rise. This seems to be mainly controlled by disequilibrium in the morphological state of the landward-narrowing estuary with some contribution from sediment autocompaction. Sea level trends of the Hugli have no apparent relation with erosion and accretion of its tidal islands.

http://nopr.niscair.res.in/bitstream/123456789/13266/1/IJMS%2040%286%29%20802-812.pdf

Sreetapa Nandy

Papers

Trend of sea level change in the Hugli estuary, India