Assessment and attribution of mangrove forest changes in the Indian Sundarbans from 2000 to 2020

Samanta, Sourav, Hazra, Sugata, Mondal, Partho P., Chanda, Abhra, Giri, Sandip, French, Jon R. and Nicholls, Robert (2021) Assessment and attribution of mangrove forest changes in the Indian Sundarbans from 2000 to 2020. Remote Sensing, 13 (24). ISSN 2072-4292

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Abstract

The Indian Sundarbans, together with Bangladesh, comprise the largest mangrove forest in the world. Reclamation of the mangroves in this region ceased in the 1930s. However, they are still subject to adverse environmental influences, such as sediment starvation due to migration of the main river channels in the Ganges–Brahmaputra delta over the last few centuries, cyclone landfall, wave action from the Bay of Bengal—changing hydrology due to upstream water diversion—and the pervasive effects of relative sea-level rise. This study builds on earlier work to assess changes from 2000 to 2020 in mangrove extent, genus composition, and mangrove ‘health’ indicators, using various vegetation indices derived from Landsat and MODIS satellite imagery by performing maximum likelihood supervised classification. We show that about 110 km 2 of mangroves disappeared within the reserve forest due to erosion, and 81 km 2 were gained within the inhabited part of Sundarbans Biosphere Reserve (SBR) through plantation and regeneration. The gains are all outside the contiguous mangroves. However, they partially compensate for the losses of the contiguous mangroves in terms of carbon. Genus composition, analyzed by amalgamating data from published literature and ground-truthing surveys, shows change towards more salt-tolerant genus accompanied by a reduction in the prevalence of freshwater-loving Heiritiera, Nypa, and Sonneratia assemblages. Health indicators, such as the enhanced vegetation index (EVI) and normalized differential vegetation index (NDVI), show a monotonic trend of deterioration over the last two decades, which is more pronounced in the sea-facing parts of the mangrove forests. An increase in salinity, a temperature rise, and rainfall reduction in the pre-monsoon and the post-monsoon periods appear to have led to such degradation. Collectively, these results show a decline in mangrove area and health, which poses an existential threat to the Indian Sundarbans in the long term, especially under scenarios of climate change and sea-level rise. Given its unique values, the policy process should acknowledge and address these threats.

Item Type: Article
Additional Information: Funding Information: Funding: This research was funded under the “Towards a Sustainable Earth: Environment-human systems and the UN Global Goals” (TaSE) program in the project “Opportunities and trade-offs between the SDGs for food, welfare and the environment in deltas”. Funding was provided by NERC Grant NE/S012478/1, Formas Grant 2019-00045, and the UKIERI-DBT (Grant No. BT/IN/TaSE/70/ SH/2018-19) under UK-India Education Research Initiative. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Uncontrolled Keywords: erosion,mangrove health,relative sea-level rise,remote sensing,salinity,tropical cyclones,earth and planetary sciences(all) ,/dk/atira/pure/subjectarea/asjc/1900
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Depositing User: LivePure Connector
Date Deposited: 30 Nov 2021 01:44
Last Modified: 22 Mar 2022 14:41
URI: https://ueaeprints.uea.ac.uk/id/eprint/82452
DOI: 10.3390/rs13244957

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