Sundarban Biosphere Reserve Research Articles

A Multi-decadal Comparative Analysis of a Set of Physicochemical and Nutrient Parameters in the Tropical Tidal Creeks of Indian Sundarban Mangrove Biosphere Reserve

Salinity, pH, dissolved oxygen (DO), dissolved inorganic nitrate (DIN), dissolved inorganic phosphate (DIP), and reactive silicate (DSi) concentrations were measured in three tidal creeks in the Sagar Island (situated within the Sundarban Biosphere Reserve, India) during 2016–17, once in a month throughout an annual cycle. The present observations were compared with a study carried out three-decade ago in the same locations during 1988–89. There was no significant difference in salinity between the years 1988-89 and 2016-17. Compared to the 1988–89 scenario, pH reduced considerably during 2016–17, indicating the dominance of heterotrophic activities over autotrophic processes. The comparative analysis shows that DO varied between 3.8 mg l− 1 and 5.4 mg l− 1 during 1988–89, which went to hypoxic levels (< 2 mg l− 1) during 2016–17. Such hypoxic conditions can lead to direct mortality of several marine biotas that thrives in these creeks. DIN and DSi concentrations reduced significantly. Compared to the 1988–89 scenario, DIN and DSi concentrations reduced by three times and ten times, respectively, in the year 2016-17. DIP concentration showed an increase in annual mean concentration, which was statistically not significant. Despite that DIN:DIP ratio reduced significantly during 2016–17 compared to that of 1988–89, which can lead to changes in the primary productivity potential of the phytoplankton community. Such changes in concentrations of the physicochemical and nutrient parameters can adversely affect the sustenance of several aquatic life forms and lead to changes in species composition or total abandonment.

First report of the fish family Pomacentridae (Damsel fishes) from Sunderban biosphere reserve, India

Sundarban Biosphere Reserve is the largest single strand mangrove forest in the world and houses 350 species of fishes. The present work reports the presence of Indo-Pacific Sergeant fish (Family Pomacentridae) Abudefduf vaigiensis (Quoy & Gaimard, 1825) from the Sundarban Biosphere Reserve, West Bengal. This is the first report of this family and species from the northern Bay of Bengal region. The species was confirmed through a single specimen collected from Lothian Island in the southern side of Sundarban and the same was compared with a specimen collected from the Arabian Sea.

Assessing the degree of soil salinity in the Indian Sundarban Biosphere Reserve using measured soil electrical conductivity and remote sensing data–derived salinity indices

The Sundarban Biosphere Reserve (SBR) in India is vulnerable to soil salinity issues arising out of the occurrence of regular floods and storm surges. While much research has investigated various geo-hazards in this Reserve, the soil salinity aspect has remained underemphasized. This study assesses the degree of soil salinity and its spatial distribution in the SBR, using remote sensing and field measured datasets. Eight soil salinity indices extracted from satellite images were statistically correlated with measured electrical conductivity values using the Pearson correlation coefficient. Through this, the Salinity Index (SI–3) and the Normalized Difference Soil Index (NDSI) were determined as the most suitable indices to map the SBR’s soil salinity. The spatial analysis of these indices revealed that the administrative Blocks of Patharpratima, Basanti, Kultali, Sagar, Sandeshkhali-I, Gosaba, and Haroa experienced extremely high level of soil salinity and salt intrusion. The high drainage density and close proximity of these blocks to rivers fosters such high soil salinity. The study calls for efficacious policy measures to lessen the effects of soil salinity on the subsistence prospects of the coastal communities. The methodology adopted in this study can be utilized for similar analysis in other saline-affected areas at various spatial scales.

Assessing the groundwater quality of the coastal aquifers of a vulnerable delta: A case study of the Sundarban Biosphere Reserve, India

The Sundarban Biosphere Reserve (SBR) of India lies in the southwestern part of the Ganges Brahmaputra delta. The SBR, traversed by tidal creeks and rivulets, suffers perennially from the scarcity of freshwater in spite of heavy precipitation in monsoon months. Rivers in Sundarbans are saline in nature with brackish groundwater in the subsurface. Fresh groundwater is mainly available from the confined aquifers and occurs at a depth range of 160–400 m below ground level. The 4.43 million population in the SBR depend fully on deep groundwater to meet their drinking water demand. It is, therefore, necessary to assess the quality of groundwater to fulfil the sustainable development goal. The water quality index (WQI) has been estimated for shallow and deep aquifers based on water quality parameters like pH, TDS, EC, Cl, SO4, HCO3, TH, Ca, Mg and Na. The dominant cations are found in the order Na > Mg > Ca, and dominant anions in the order HCO3>Cl > SO4. The groundwater in the SBR region belongs to NaHCO3, NaCl and mixed type hydro-geochemical facies. The Cl/HCO3 ratio indicates that the shallow aquifers are affected by the saline water intrusion. Following the limit set by the Bureau of Indian Standards, the shallow groundwater in the SBR is found to be unsuitable for drinking. Although the deep groundwater is within the permissible limit of safe drinking water, its quality is poor. The Coastal Regulation Zone notification of 2011 has identified the SBR region as ‘Critically Vulnerable Coastal Area’ and restricted the use of deep freshwater for drinking purpose only. The paper argues that to meet the goal of sustainable development and safe drinking water for all in the future, extensive rainwater harvesting and supply of treated surface water through pipeline and desalination of subsurface brackish water are some of the feasible options in the region.

WITHDRAWN: Deciphering preferable adaptation strategies for climate change induced coastal hazards in Indian Sundarban Biosphere Reserve

WITHDRAWN: Deciphering preferable adaptation strategies for climate change induced coastal hazards in Indian Sundarban Biosphere Reserve

Analyzing climate variability and its effects in Sundarban Biosphere Reserve, India: reaffirmation from local communities

Climate variability and continual occurrence of cyclones, flood and storm surge have greater implications on fragile ecosystem of Indian Sundarban Biosphere Reserve (SBR). Centurial meteorological data were used to assess the climate variability in the Reserve. Multivariate principal component analysis was performed to identify the consistency among the conditioning parameters of climate. Cyclones, severe cyclone, storm surge height, salinity intrusion, pH and surface water temperature were assessed to figure out the overall consequences of climate variability. Field investigation from 570 households from coastal and inland blocks (administrative division of the district) was carried out to reaffirm the variability in climatic conditions and its environmental, economic and social consequences in SBR. Study revealed wide spatiotemporal variation in temperature and rainfall. Rise in sea level, flood and high storm surge height and salinity intrusion were inducing vulnerability in the coastal blocks. Communities in Gosaba, Kultali, Kakdwip, Sagar, Patharpratima and Namkhana blocks largely showed high level of agreement for climate variability. Hence, the study calls for effective adaptation and mitigation strategies.

Assessment of changes in land use, land cover, and land surface temperature in the mangrove forest of Sundarbans, northeast coast of India

This paper investigates the impacts of changing land use–land cover on the land surface temperature (LST) and normalized differential vegetation index (NDVI) distribution in the Indian part of the Sundarbans Biosphere Reserve by utilizing remote sensing and geographical information system. Landsat Thematic Mapper (TM), Enhanced Thematic Mapper (ETM+) and Operational Land Imager images of the year 2000, 2010 and 2017, respectively, were used to assess the essential indicators for regional environmental health employing appropriate calibrations and corrections. It was observed that there has been a marked reduction in the areas of plantation, mangrove swamp, mangrove forests and agricultural land since 2000. In contrast, an increase in sand beach, waterlogged areas, mudflat, river, and agriculture area was observed. The mean NDVI values for mangrove forests and plantation have decreased from 0.441 to 0.229 and 0.266 to 0.195, respectively, while river, aquaculture, agricultural and open scrubs classes had higher values. The rate of increase in surface LST was highest over settlements, followed by sand beaches, mudflats, aquaculture, mangrove forest, river, plantations, waterlogged areas and agricultural field. LST showed a negative correlation with NDVI values probably due to the high rate of evapo-transpiration activities of the mangrove vegetations. All these above facts distinctly substantiates that there is an increase in open patches/non-vegetated cover and that the ecosystem is under constant stress.

Exploring effectiveness of frequency ratio and support vector machine models in storm surge flood susceptibility assessment: A study of Sundarban Biosphere Reserve, India

The Sundarban Biosphere Reserve (SBR), which is one of the important coastal regions of India, is vulnerable to storm surge hazards. It experiences storm surge flood of varying magnitudes every year causing immense loss to life and property. Thus, an accurate storm surge flood susceptibility assessment in the Reserve is essential for safeguarding the coastal communities. The present study attempts to explore the effectiveness of the conventional frequency ratio, modified frequency ratio and support vector machine (SVM) models in storm surge flood susceptibility analysis. Core areas of the SBR and some areas along rivers experience very high and high susceptibility. Moderate susceptibility was prevalent in the north, north-western and some areas in the south-western parts of the Reserve while low susceptibility was observed in the western part of the Reserve (located away from the coast). The maps were validated using the receiver operator characteristic (ROC), the seed cell area index (SCAI), and the spatially agreed area approach. The area under the success rate (0.8347) and prediction rate (0.8221) curves was highest for the SVM model. Frequency ratio and modified frequency ratio models showed 71.2% spatially agreed area of susceptibility. The spatially agreed area of susceptibility was lower (65.1%) in case of modified frequency ratio and the SVM model while it was highest (83.2%) between the modified frequency ratio and SVM models. Thus, the SVM model was found to be the best fit model for analyzing storm surge flood susceptibility in SBR.

Assessing socio-economic vulnerability to climate change-induced disasters: evidence from Sundarban Biosphere Reserve, India

ABSTRACT Indian Sundarban Biosphere Reserve (SBR), a fragile ecosystem, is susceptible to frequent cyclones, floods, and storm surge. The study impeccably analyzed the socio-economic vulnerability in SBR using pragmatic approach. Average storm surge height, slope amount, flood inundation, drainage proximity, and drainage density were used for assessing exposure while sensitivity and adaptation were examined from the data derived through a comprehensive field survey of 570 households in SBR. The revelation of the study manifested very high vulnerability in Basanti, Gosaba, Kultali, Namkhana, and Patharpratima blocks and high vulnerability in Kakdwip, Sagar, and Hingalganj blocks of SBR. Constant exposure to cyclones and storm surges, frivolous infrastructural setup, impoverish social structure, and lamentation of losses are major barriers to overall socio-economic upliftment of communities. Consolidated infrastructural setup, proper early warning system, disaster monitoring centres, better transport connectivity within remote islands, better livelihood opportunities, education, and awareness may help in improving the socio-economic conditions of the communities. Pragmatic approach assisted in the cogent understanding of climate change impacts and indicated adaptive and mitigation measures to improve coastal society in SBR. Thus, the approach has proven to be effective for analyzing the impact of climate change-induced hazards on socio-economic condition on the communities in coastal areas.

Ecosystem service valuation of a natural reserve region for sustainable management of natural resources

Abstract The mangrove ecosystem is extremely important for providing essential ecosystem services, which are crucial for subsistence and human well-being. Using time-series satellite data products and different unit values, the spatially explicit Ecosystem Service Value (ESV) of six eco-regions of the Sundarbans Biosphere Reserve (SBR), India, has been calculated for four reference years, viz. 1973, 1988, 2002 and 2013. The maximum ESV (million US$ year1) is provided by the mangrove forest (2292–44468), followed by water surface (65–4244), cropland (26–3938), and sparse vegetation cover (0–326). The total ESV (million US$ year1) of Sundarbans is estimated to be 16629.5, 20175.7, 19733.4, and 16761.3 for 1973, 1988, 2002, and 2013 respectively. The regulation of gas and climate, raw material production, and cultural ecosystem services are entirely dependent on the mangrove ecosystem, while the waste treatment, cultural, and water regulation services are found to be highly sensitive to the changes in water bodies. The food production and biodiversity services exhibiting higher sensitivity to the changes in cropland, water regulation and soil formation and retention services show higher sensitivity to the changes in mixed vegetation cover. The current study has thoroughly evaluated the sensitivity and response behavior of six ecoregions of Sundarbans. The outcome of this study will enable the decision-makers, planners, as well as researchers to adopt necessary action plans for strengthening and protecting the natural resources of this biosphere reserve.

Responses of the mangrove ecosystem to Holocene environmental change in the Sundarban Biosphere Reserve, India

Abstract The Sundarban Mangrove Forest in the Sundarban Biosphere Reserve, located at the mouth of the Ganga–Brahmaputra Delta in India, is the most diverse mangrove ecosystem in the world. Sediment cores were taken from two widely separated islands in that reserve: Chamta (CMT) and Sudhyanyakhali (SDK). Pollen analysis and radiocarbon dating were used to study the Holocene development and dynamics of this unique ecosystem. Modern pollen rain study reveals a strong relation between modern pollen rain and the present vegetation, as well as a high rate of Phoenix palludosa pollen production.The pollen records indicate that man-grove existed at CMT from ~5960 and at SDK from ~1520 cal yr BP. Changes in relative sea level, including the frequency and intensity of inundation as well as fluctuating precipitation, have been the major factors along with geomorphic processes that control the development and dynamics of the mangrove in the area during the Holocene. The mid Holocene mangrove at CMT declined, to be progressively replaced by successive communities, and eventually reached climax stage, while the SDK site is transitional in nature. The mangrove responds rapidly to changes in environmental conditions at both locations. Because of large-scale anthropogenic interventions, it is unlikely that similar rapid responses will occur in the future.

Assessment of Cyclone Vulnerability, Hazard Evaluation and Mitigation Capacity for Analyzing Cyclone Risk using GIS Technique: a Study on Sundarban Biosphere Reserve, India

Cyclones are one of the devastating natural hazards in the earth that have extensive consequences on both life and livelihood. Assessment of cyclone risk is important not only for the survival of people but also for designing adaptation strategies in major cyclone-prone areas. Risk can be defined as the integrated function of vulnerability, hazard, and mitigation capacity. Risk assessment is a very protracted task needing analysis of multiple factors which are also changes with changing geographical location. Thus, we applied the multi-criteria decision-making technique to assess the block-level risk to cyclone in the Sundarban region, India. The weight-based analysis reveals that nearness to coastline and distance from cyclone tract have the greatest vulnerability exposure; windspeed has the highest hazard score; and nearness to cyclone shelter and cyclone awareness, on the other hand, has utmost mitigation capacity to cyclone risk analysis. The risk analysis shows that out of the total blocks (19) in the Sundarban, nearly half of the blocks are with very high to moderate cyclone risk with the least mitigation capacity to cope with such natural hazards. The blocks like Gosaba and Kultali to be found in the southern portions and nearby to the coast exposed more risk to cyclone while those situated farther to the coast in the central and northern parts exposed low risk. The findings of the present study may have high implications for developing more mitigation capacity in a very-high- to a moderate-cyclone-risk area. Therefore, the applied approach can help the local authorities in identifying vulnerable and hazard areas and building actionable strategies for mitigation and reworked copy of cyclone hazards in the Sundarban Biosphere Reserve.

Human–wildlife conflicts in the Sundarban Biosphere Reserve and the politics of forest conservation

The aim of this paper is to identify the politics of forest conservation—processes through which formal stewardship methods are legally enforced circumventing customary community rights to the forests. Drawing on an ethnographic fieldwork conducted in the Sundarban Biosphere Reserve of West Bengal, this paper discusses the ways in which such bureaucratic provisions of forest conservation shapes ideologies about human–wildlife conflicts in India. The paper draws on empirical lessons and provides observations on the different kinds of forest notifications and their impacts on the customary rights of the forest-dependent communities in the Sundarbans. Although it has been widely established that forest conservation adversely impacts local livelihoods and results in dispossession from subsistence resources, it is indeed imperative to understand that in legitimising forested landscapes as ‘protected’ and inviolate, survival of different communities is also at stake.

Mapping mangroves using LISS-IV and Hyperion data in part of the Indian Sundarban

ABSTRACTMangroves in different part of the globe including world’s largest halophytic population in Sundarban are under tremendous pressure due to global warming, sea level rise, natural disasters and ever-increasing influence of human population. In such an alarming situation conservation of mangrove population has been recommended by the experts. Species-level mapping of mangroves is one of the important steps for sustainable conservation of mangrove ecosystem. This study demonstrates the efficiency of a combination of Hyperion hyperspectral and IRS Resourcesat-2 LISS-IV multispectral data for discriminating and mapping some mangrove species at Lothian Island and Saptamukhi Reserve Forest located in the western part of Sundarban Biosphere Reserve of India. The spectral signature drawn on Hyperion data helped to extrapolate field samples of various pure pixels of the mangrove plant species using a region growing approach. Those training samples were used to apply Object-based Image Analysis (OBIA) classification on 5 m spatial resolution LISS-IV data. Mostly dominant mangrove species like Aegialitis rotundifolia, Aegiceras corniculatum, Avicennia community, Ceriops community, Excoecaria agallocha, Lumnitzera racemosa and Phoenix paludosa have been successfully classified along with other associated landuse/landcover in these islands. The methodology used in the study has a huge potential in identification, mapping and management through restoration of mangroves in difficult terrain like the Sundarban.

Ecosystem service value assessment of a natural reserve region for strengthening protection and conservation

Ecosystem Services (ESs) refer to the direct and indirect contributions of ecosystems to human well-being and subsistence. Ecosystem valuation is an approach to assign monetary values to an ecosystem and its key ecosystem goods and services, generally referred to as Ecosystem Service Value (ESV). We have measured spatiotemporal ESV of 17 key ESs of Sundarbans Biosphere Reserve (SBR) in India using temporal remote sensing (RS) data (for years 1973, 1988, 2003, 2013, and 2018). These mangrove ecosystems are crucial for providing valuable supporting, regulatory, provisioning, and cultural ecosystem services. We have adopted supervised machine learning algorithms for classifying the region into different ecosystem units. Among the used machine learning models, Support Vector Machine (SVM) and Random Forest (RF) algorithms performed the most accurate and produced the best classification estimates with maximum kappa and an overall accuracy value. The maximum ESV (derived from both adjusted and non-adjusted units, million US$ year−1) is produced by mangrove forest, followed by the coastal estuary, cropland, inland wetland, mixed vegetation, and finally urban land. Out of all the ESs, the waste treatment (WT) service is the dominant ecosystem service of SBR. Additionally, the mangrove ecosystem was found to be the most sensitive to land use and land cover changes. The synergy and trade-offs between the ESs are closely associated with the spatial extent. Therefore, accurate estimates of ES valuation and mapping can be a robust tool for assessing the effects of poor decision making and overexploitation of natural resources on ESs.

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

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.

A new species from the genus Astochia Becker, 1913 (Diptera: Asilidae) from the Sundarban, India with an updated checklist of Indian species

ABSTRACTA new asilid species Astochia venkataramani sp. nov. is described with supportive illustrations of male genitalia and body parts, from Sundarban Biosphere Reserve, West Bengal, India. An updated checklist of the Indian species of Astochia Becker is also included. The holotype specimen of the new species has been deposited in the National Zoological Collections of Zoological Survey of India, Kolkata. An updated identification key to the species of Astochia from West Bengal is also provided.http://www.zoobank.org/urn:lsid:zoobank.org:pub:D36A20CC-9D56-4050-912E-2E846D5F6E91

Cost–benefit analysis of ‘Blue Carbon’ sequestration by plantation of few key mangrove species at Sundarban Biosphere Reserve, India

Climate change and global warming have a destabilizing effect on the global environment, and governmental statutory bodies are emphasizing a reduction of emission coupled with restoration of degraded forest lands as a carbon sequestration–emission reduction (REDD+) initiative. Asphyxiated mangrove soil, existing on the borderline of land and sea, has the highest potential to trap ‘blue carbon’; hence, plantation programs have been initiated around the tropical coasts to restore this unique habitat. This case study provides a cost–benefit and carbon sequestration analysis for planting of five mangrove species (Avicennia marina, Bruguiera sexangula, Ceriops tagal, Rhizophora mucronata and Xylocarpus moluccensis) by various methods in a 102.4-ha area at the Indian Sundarbans. It is estimated that as per the planting methods used in the current study and physio-chemical properties of the sediment, coupled with other local factors such as anthropogenic interventions, Avicennia marina planting by the ‘propagule dibbling’ method is the most cost effective (0.002 Euro/survived plant), with the highest increment (97%) in organic carbon density (OCD), humic acid (100.86%) and fulvic acid (48.78%) over a period of 5 years. Survival rate was highest (82%) for Avicennia marina, planted by the ‘transplanting of nursery-grown seedlings’ method. The drain and trench method resulted in a 55% survival rate for Rhizophora mucronata, but the extra labor investment made this the costliest method (0.13 Euro/survived plant) and also less carbon effective (only 85% increment of OCD in 5 years). Planting methods, sediment quality, tidal inundation and salinity variations can play a major role in blue carbon burial/sequestration in mangrove lands.

Vulnerability to storm surge flood using remote sensing and GIS techniques: A study on Sundarban Biosphere Reserve, India

Assessment of vulnerability to storm surge flood is not only significant for the survival of the exposed communities but also for adaptation. Defining vulnerability as the function of exposure, sensitivity and resilience capacity, we propose a composite vulnerability index (CVI) to assess village- level vulnerability to storm surge flood in the Sundarban Biosphere Reserve (SBR), India. The composite vulnerability index based analysis revealed that of the total villages (1063) located in SBR; nearly half of the villages are highly and very highly vulnerable with least capacity to cope with any kind of extreme event. The villages located in the southern parts and adjacent to coast were found more vulnerable to storm surge while those located at higher elevation in the central part showed low vulnerability. Some villages in northern part of the region were under high and very high vulnerability due to presence of low lying and waterlogged wetlands. The findings of the study may have implications for developing resilience capacity in response to storm surge flooding. Thus, the methodology can help the local policymakers in integrating local multi-hazards knowledge and in making information actionable for mitigation and adaptation of storm surge flood hazard.

A paradox of the ‘community’: contemporary processes of participatory forest conservation in the Sundarban Biosphere Reserve (SBR) region of West Bengal

ABSTRACTThis article provides a comprehensive critique of the culturalist idealizations of community, associated with an essentially tenuous version of environmentalism. To this end, it analyses an ‘eco-governmentality’, observed in the implementation of joint forest management (JFM) policy in India and, in doing so, engages with a rethinking on the historical definitions of community. An explanation of community, popularized by the works of pioneering sociologists like Ferdinand Tonnies and Louis Wirth, had largely built on some immutable dimensions. Most of such dimensions offered are organized on the notion that communities are intractable as well as organic, inhabit a distinct geographical location and have a socio-cultural system relatively undisturbed by external forces. The present study, based on empirical observations from the eco-governmentality of JFM in India, brings in insights to critique the aforementioned line of thought. It offers two levels of insights: (1) a collective can represent itself as a community through shared experiences of marginalization as well as subject-formation, (2) the solidarity of a collective as a community is often invoked as a ‘moral rhetoric’, to ‘exploit the political obligations that the government have for looking after the poor and the underprivileged section of the population’.1