Abstract

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.

Highlights

  • Mangroves are diverse and highly productive ecological communities [1,2], which provide important ecosystem functions [3,4]

  • According to [27], 24 true mangrove taxa belonging to nine different families are found within the Indian Sundarbans

  • According to [40,45] the most accurate combination of sensor and image processing method is Landsat data and principal component analysis (PCA), using band ratios, if discrimination between mangrove and non-mangrove covered areas is required over a large area

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Summary

Introduction

Mangroves are diverse and highly productive ecological communities [1,2], which provide important ecosystem functions [3,4]. Located at the land-sea interface, they protect coastal areas against natural hazards such as cyclones and tsunamis [5,6,7,8]; they retain terrestrial sediment and recycle nutrients, supporting clear offshore waters, which in turn favors the photosynthetic activity of phytoplankton as well as growth and robustness of coral reefs, seagrass beds and reef fish communities [9]; they serve as an important habitat, nursery and refuge, providing food for countless organisms including humans [4] These ecosystems are vital carbon sinks, either storing carbon temporarily within organic peat soils, or as dissolved organic carbon in ocean sediments at greater depths, offsetting climatic-active greenhouse gasses for longer periods [10]. This requires a reconfiguration of development paradigms and an internalization of anthropogenic and climatic drivers of change and their cumulative impacts on the socio-ecological system

Study Area
Data and Methods
16 Miles to 1 Inch
Historical Overview of the Sunderbans’ Development
Post-Colonial Policies
Internal Mangrove Dynamics—Climate Change and Human Impacts
Findings
Conclusions
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