Sagar Island Research Articles

Evaluation of groundwater quality by adopting a multivariate statistical approach and indexing of water quality in Sagar Island, West Bengal, India.

In the vicinity of the coast, predominantly groundwater is the sole reliable resource for potable purposes as the surface water sources are highly saline and unfit for human consumption. However, the groundwater in Sagar Island is highly vulnerable to saltwater intrusion. The majority of drinking water comes from government-owned hand pump-equipped tube wells. But during the summer season, many of these tube wells yield significantly less water. Hence, in the current scenario, water quality assessment has become important to the quantity available. Total of 31 samples of deep tube wells (groundwater) are collected at variegated locations during pre-monsoon season throughout Sagar, and then, the physical and chemical quality parameters of these water samples are analysed. Furthermore, a multivariate statistical technique is executed with the aid of the SPSS program. The hydro-chemical parameters that are taken into account for the quality analysis are pH, salinity, electrical conductivity (EC), total dissolved solids (TDS), total hardness, aluminium, arsenic, bi-carbonate, cadmium, iron, chloride, copper, chromium, cobalt, lead, magnesium, manganese, nickel, potassium, sulphate, zinc, and sodium. Then, the analysed data evaluates the water quality index (WQI). Five components are identified through the principal component analysis (PCA) technique, and 82.642% total variance is found. The outcomes of the quality assessment study illustrate that about 54.84% of collected samples come in the "excellent" water quality class when calculated by the "weighted arithmetic WQI method," and 90.32% of collected groundwater samples come in the "good" water quality class when computed using the "modified weighted arithmetic WQI method." This study helps for the interpretation of WQI to assess groundwater quality.

Evaluation of overwash vulnerability and shoreline dynamics in cyclone-prone Sagar Island, Sundarbans (India)

Situated in the climatically vulnerable Sundarbans region, Sagar Island has increasingly been subjected to intense cyclonic events, including Yaas, Amphan, Bulbul, and Aila, leading to significant alterations in its coastal morphology. This study aims to elucidate the overwash vulnerability and shoreline dynamics in Sagar Island, spanning the period from 2000 to 2020. Utilizing satellite imagery, the study employs three indices—Overwash Shoreline Ratio (OSR), Maximum Overwash Intrusion Recurrence (MOIR), and Complete Barrier Overwash (CBO)—to assess overwash vulnerability. These indices collectively indicate a heightened susceptibility to overwash intrusion, with a particular focus on the years following severe cyclonic events. Additionally, shoreline change dynamics were quantitatively analyzed using the Digital Shoreline Analysis System (DSAS) tool, revealing a strong positive correlation between shoreline recession and climatic variables. Interlinkages between overwash vulnerability and shoreline dynamics were established, confirming that both phenomena are exacerbated by climate change and extreme weather events. The study's findings have critical implications for a broad range of sectors such as agriculture, fisheries, transportation, and ecosystem conservation. The research underscores the urgency for an integrated coastal management strategy that considers both overwash vulnerability and shoreline change dynamics to enhance sustainability and resilience. This study contributes to the global discourse on coastal dynamics, serving as a benchmark for climate adaptation measures in other cyclone-prone regions.

OSCILLATION OF HYDROLOGICAL PARAMETERS IN SHRIMP PONDS WITHIN MANGROVE-DOMINATED INDIAN SUNDARBANS

The survival rate of Penaeus monodon was monitored for a decade (2010-2019) in two shrimp culture ponds at Chemaguri located at Sagar Island in the Indian Sundarbans delta complex. The two ponds exhibited significant variations in terms of the survival rate of the cultured species, which is attributed to variations in nitrate, phosphate, and dissolved oxygen. The root cause of such difference is related to variation in stocking density of the cultured species (10 PL20/m2 in pond 1 and 25 PL20/m2 in pond 2) which resulted in the generation of nutrients (except silicate) and alteration of Dissolved Oxygen (DO). Optimization of stocking density and introduction of a biotreatment pond may restore and ecologically balance the situation in the shrimp culture sector of the Sundarban region.

CARBON STORAGE POTENTIAL OF DOMINANT MANGROVES IN WESTERN INDIAN SUNDARBANS

The Indian Sundarbans are noted for luxuriant mangrove diversity that is known to scrub carbon dioxide from the atmosphere. Precise estimation of the biomass of these species is necessary for evaluating the carbon storage pattern in the mangroves of the lower Gangetic belt. The plant biomass estimation was carried out for an average of 25 trees in 15 (10 m × 10 m) plots from the intertidal mudflats of Chemaguri (southeast portion of Sagar Island) in low tide conditions from 10th to 15th September 2022. The estimated biomass was of the order Sonneratia apetala > Avicennia alba > Avicennia marina > Excoecaria agallocha > Avicennia officinalis. The stem, branch, and leaf biomass of each species were converted into carbon by multiplying with a factor of 0.45 as per the standard procedure. The deviations observed in the results obtained from both studies call for the standardization of the process.

Climate change and agriculture in a coastal region: A case study of betel leaf cultivation in Sagar Island, Kakdwip, South 24 Parganas

Agriculture is a function of temperature and precipitation. Any change in these parameters, above and below the threshold value, will affect photosynthesis and transpiration in the crops, leading to an overall negative impact on agriculture, threatening global food security. Underdeveloped and developing worlds are most likely to be affected due to this situation because more than 80% of the population in this area is economically dependent on agriculture. With this background in mind, the present study attempts to delve into the impact of climate change on betel leaf cultivation in the study area because it forms the backbone of the local economy. Low lying coastal areas bear testimony of the primary evidences of climate change. The study area, therefore, is an ideal location to study the impact of climate change as it is situated in the path of frequent extreme weather phenomena. Such areas are particularly vulnerable to climate change in the form of sea level rise in response to increased precipitation resulting out of rise in temperature. The sensitivity of betel leaf to minor fluctuations in climatic parameters and its economic importance in the selected study area justifies the theme of enquiry. The present paper analyses meteorological data on temperature and rainfall along with field observation to investigate the issue. Given the sensitivity of betel leaf to such changes, an adverse impact on its production seems inevitable. However, findings of the present study prove otherwise. Firstly because the rise in temperature is less than 1.5 degree centigrade, which according to IPCC is the threshold value for impact on agriculture. Secondly, the adoption of adaptive strategies like use of fertilizer, soil treatment etc. practiced in the area largely offsets the adverse impact of climate change on crop production. However, the impacts are not entirely escapable.

Developing assessment flow for damage estimation of mud housing typology through a case study against coastal floods

Rising instances of prolonged inundation due to climate-aggravated high tide flooding are economically burdensome for resource-crunched developing nations that bear enormous damage due to loss of built infrastructure (housing in this case). Regardless of the loss, coastal flood impact on buildings is rarely given precedence. The mud building typology in India captures 34% of existing housing demand primarily within ruralIndia; for instance, 75% of the housing in Sagar Island uses mud as the dominant construction material, making it an ideal case for the proposed research. The multivariate nature of damage and empirical data constraint associated with mud buildings propels the development of two unconventional damage assessment approaches using multivariate-probabilistic technique. The proposed literature-based approach uses logical reasoning based on the available scientific evidence whereas the lab-based approach uses the insights from structural analysis of scaled model. The damage matrix created from both the approaches are used to analyse a common flood data (depth & duration) generated using 1000 Montecarlo simulations. The resultant Damage Stage values confirm the versatility of either approach over spatial (local to regional)—temporal (flood character and intensity) dimensions. The lab-based approach proved to be a better alternative considering the availability of continuous records on damage behaviour and precise information on the flood threshold of dominant building material, a crucial component of the multivariate damage assessment process.

Land scarcity and land access in a hazard‐prone island: Sagar, Indian Sundarbans

The analytical inseparability of natural environment and society is reiterated by the findings of this study which contributes to a genre of studies that centre‐stages the socio‐ecological system. This study seeks to understand the interplay of state‐related and other modes of securing property rights in the context of pervasive coastal hazards through a case study from the Indian Sundarbans region (Sagar Island in West Bengal). This paper also contributes to research pertaining to slow‐onset disasters and attempts to examine emerging dimensions of land scarcity as well as diverse modes of access to land in the context of progressive ecological vulnerability. The analysis highlights the varying shades of declining land access and investigates how existing land policies and disaster management mechanisms remain far from extending security to communities experiencing environmental crisis. The paper thereby examines how community and state agencies adopting means to allocate property may in fact refute legality and perpetuate informality.

Soil site suitability for sustainable intensive agriculture in Sagar Island, India: a geospatial approach

Soil site suitability for sustainable intensive agriculture in Sagar Island, India: a geospatial approach

Notes on the large carpenter bees, genus Xylocopa Linnaeus, 1758 (Hymenoptera: Apidae) from Sagar Island, India

Notes on the large carpenter bees, genus Xylocopa Linnaeus, 1758 (Hymenoptera: Apidae) from Sagar Island, India

Regional Environmental Change, Farmers’ Perceptions and Resilient Farming: Experiences from the Sagar Island of Indian Sundarbans

This research analyzed the patterns of agricultural transformations and adjustments to rapid environmental changes in deltaic island ecosystems by considering the case of Sagar Island of Indian Sundarbans using decadal climatic datasets, geospatial information, and farmers’ perceptions. Farmers’ cognition was considered for identifying crops that were suitable for cultivation in the changing environment. Results indicated that the average annual temperature and precipitation in this region had increased notably since 1980. Similarly, surface soil salinity had also recorded an overall increase throughout the island during the last three decades. In such a scenario, local farmers were only able to profitably cultivate few salinity-tolerant varieties of paddy (e.g., Masoori, Kalma, Santoshi, and Pratiksha) and vegetables (e.g., sunflower, potato, onion, okra, and betel leaf). Brackish water aquaculture had also become popular here in spite of its socio-ecological detriments. Many farmers were found to use their traditional knowledge proficiently alongside modern methods. However, the pressure of local peers, lack of readily investable wealth, and appropriate technological expertise often weakened their adaptive capacity. The findings suggested that effective cropping strategies such as coupled mangrove-shrimp farming and cultivation of salinity as well as waterlogging tolerant crop varieties could be considered as viable strategies toward enhancing resilience.

Characteristics of astronomical tides and their modulation on sea level extremes along the Indian coast

In this study, long-term hourly sea-level records from 18 tide gauge stations during 1972–2007 were analyzed to study the characteristics of astronomical tides, sea-level trends, and extremes around India's mainland. The de-tided signals were used to estimate these parameters and study tide and surge interaction. The observed sea level depicts significant variability in daily, seasonal, and inter-annual time scales. Semidiurnal tides are the most dominant among the high-frequency tides, with an amplitude of up to 2.5 m for M2 and 0.75 m for S2 tides in the northwestern and northeastern continental shelf and reduced to 0.25 m in the south. The amplitude of diurnal tides (O1 and K1)is relatively weak (<0.25m) at all the stations. The annual harmonics dominate the seasonal cycle, with an amplitude of 0.7 m at Garden Reach in the northeastern continental shelf, decreases to 0.15 m at Tuticorin in the south, and remains small (<0.1 m) along the west coast of India. The amplitude of lunar nodal and perigee tides are significantly high (up to 25 mm) at several stations compared to the long-term global mean sea level trend (∼3.3 mm/y). The sea level trend is significantly positive (up to 4 mm/y) for Sagar Island, Diamond Harbor, Haldia, and Mangalore; negative (up to −3 mm/y) for Garden Reach and Okha, and in-significant (0.5 mm/y) for Mumbai, Vishakhapatnam, and Paradip. Interaction between the semidiurnal tides and surges was intense at most stations, with a high probability of surge peaks during the fall-tide conditions in the northern continental shelf, at rising-tidal conditions for the south-eastern and western peninsula, and co-occurring at high tide for southern stations. The degree of tide-surge interaction increases from south to north with an increase in tidal range and significant nodal and perigee tidal modulation.

Vulnerability and Risk Assessment to Climate Change in Sagar Island, India

Inhabitants of low-lying islands face increased threats due to climate change as a result of their higher exposure and lesser adaptive capacity. Sagar Island, the largest inhabited estuarine island of Sundarbans, is experiencing severe coastal erosion, frequent cyclones, flooding, storm surges, and breaching of embankments, resulting in land, livelihood, and property loss, and the displacement of people at a huge scale. The present study assessed climate change-induced vulnerability and risk for Sagar Island, India, using an integrated geostatistical and geoinformatics-based approach. Based on the IPCC AR5 framework, the proportion of variance of 26 exposure, hazard, sensitivity, and adaptive capacity parameters was measured and analyzed. The results showed that 19.5% of mouzas (administrative units of the island), with 15.33% of the population at the southern part of the island, i.e., Sibpur–Dhablat, Bankimnagar–Sumatinagar, and Beguakhali–Mahismari, are at high risk (0.70–0.80). It has been concluded that the island has undergone tremendous land system transformations and changes in climatic patterns. Therefore, there is a need to formulate comprehensive adaptation strategies at the policy- and decision-making levels to help the communities of this island deal with the adverse impacts of climate change. The findings of this study will help adaptation strategies based on site-specific information and sustainable management for the marginalized populations living in similar islands worldwide.

Socio-Economic Impact Assessment at Sagar Island in Respect of Grid Availability

The focus of the paper is based on the state of West Bengal's Sundarban region. The Sundarban forests lie in the southern part of the state. It comprises 104 island groups out of which 54 are inhabited. Sagar Island, the focus of my study, is the largest island in this area having an area of 286 km2 and a population of more than 1.6 lakhs. This island is situated 5 km adrift on the mainland of India. Due to the presence of River Muriganga (Hooghly), this island could not be connected to the national grid. So, the power requirement was fulfilled by the Diesel Generator sets run by WBSEDCL, 9 Solar Photovoltaic Plants located in the strategic areas, and one Wind- Diesel Hybrid Plant run by WBREDA so that the minimum power requirement could be met. In this paper, the focus of the study will be on the people of Sagar Island on how they will be benefited from the conventional grid in order to improve their lifestyle and economy and also study the future of renewable projects and the existing off-grid system prevalent in this island. Keywords: Grid availability, Socio-economic impact assessment, Decentralized Distributed

Exploring Values and Beliefs in a Complex Coastal Social-Ecological System: A Case of Small-Scale Fishery and Dried Fish Production in Sagar Island, Indian Sundarbans

The survivability of the small-scale fishery and dried fish production in Indian Sundarbans, despite increasing threats posed by climate, environmental, economic, and policy drivers, suggests that they possess certain unique strengths and capabilities. One thread of these strengths is connected to the fact that Sundarbans’ fishery system is strongly anchored in the values and beliefs of the local fishing communities. There is, however, limited empirical information available on the prevailing individual and collective attitudes, expectations, traditions, customs, and, above all, values and beliefs that strongly influence local fishing communities of Sundarbans. This manuscript aims to address this gap by drawing on qualitative data to (1) map the nature of values and beliefs associated with the Sundarbans’ Sagar Island fishing communities who are engaged in small-scale fishery and dried fish production; and (2) highlight the contributions of values and beliefs to the small-scale fishery and dried fish production systems of Sagar Island. Our study reveals that historical factors such as the patriarchal and patrilineal system prevalent in the Indian Sundarbans as well as the current drivers, including environmental and social-economic changes, create inconsistent values and beliefs among male and female members of its society. Issues around values and beliefs are heavily influenced by social-ecological realities comprising material, relational and subjective dimensions. They can range from being strictly personal to largely community-oriented as they are shaped by realities of gender, class, power dynamics, and politics. Values and beliefs are fundamental to human perception and cognition but often get neglected in mainstream literature covering human dimensions of resource management. Our research adds weight to the theoretical and place-based understanding of the contributions of values and beliefs to the small-scale fishery and dried fish production systems. We learn from the case study that values and beliefs can act as mirrors, reflecting the current as well as future realities of small-scale fisheries and dried fish production systems and provide important directions for sustainability and viability of the entire social-ecological system that hosts this sector.

Case study of augmenting livelihood of fishing community at Sagar Island, India, through solar thermal dryer technology

Case study of augmenting livelihood of fishing community at Sagar Island, India, through solar thermal dryer technology

Climate vulnerability and economic determinants: Linkages and risk reduction in Sagar Island, India; A geospatial approach

Climate vulnerability is the propensity to be adversely affected by climatic variability and natural hazards. People of low-lying islands face accelerating physical and non-physical stresses due to their greater exposure, higher sensitivity, and lower adaptive capacity towards climate change. Being home to over 0.2 million people, Sagar Island, the largest Island of Sundarban, is highly susceptible to coastal erosion, cyclonic storm surges, flooding, and embankment breaching, causing loss of land, property, and livelihood that eventually lead to displacements and induced migration. Over the past two decades, residents of this fragile sinking island of this world's largest mangrove forest have seen their homes engulfed, farmlands salinized and livelihood depleted by the rising sea. This study investigates the association between socio-economic vulnerabilities through the contextual indicators of land loss, productivity loss, loss of livelihood, and induced migration through regression modeling to find out linkages and scopes of risk reduction. The result reflects a significant positive correlation between land loss and loss of livelihood (p 0.0494*) that negatively correlates with the occurrence of in-migration (z −0.826), while the correlation between productivity loss and loss of livelihood is 0.6318. Mouzas like Dhablat, Shibpur, Beguakhali show outlier characteristics due to severe rates of erosion and embankment failure. The secondary data from the India Meteorological Department, National Centre for Ocean Information Services, have been used to identify considerable changes from cumulative erosion and accretion employing statistical and GIS techniques. This bottom-up assessment can contribute to disaster management and policy implications by identifying the particular intercession at the mouza level that increases the resilience of these vulnerable communities to climate change.

Bioturbation by crab populations vis-à-vis sediment dispersal in Sagar Island, Hugli Estuary, India

Bioturbation by crab populations vis-à-vis sediment dispersal in Sagar Island, Hugli Estuary, India

The deadliest tropical cyclone ‘Amphan’: investigate the natural flood inundation over south 24 Parganas using google earth engine

Climate change is hammering the environment, socio-economic condition, vegetation degradation, earth surface change and over the land losses. In between 2019 and 2020, West Bengal people are facing three major cyclones like, Fani, Bulbul and the last was Amphan. Those natural disasters were affected in vegetation, hammering crop production, water quality change, life losses and affected in the ecosystem. 20th May 2020 Amphan was entering in West Bengal and occur several damaged. Seventy two people of West Bengal were lost their life and several months over the southern parts of West Bengal are facing huge land scarcity and salt-water intrusion on the mainland. Over 13.6 billion dollar was losses due to this cyclone. Google Earth Engine (GEE) is a cloud-based platform to detect earth observation using high spatial satellite data with planetary-scale analysis capabilities. C-band Sentinel-1A Synthetic Aperture Radar is used to identifying the flood inundation on Google Earth Engine (GEE). Landsat 8 OLI data is used for MNDWI calculation on this area. Pre-Amphan and during Amphan two satellite data are clearly showing the water increased area. The Coastal area like Sagar Island (154.254 Sq.km), Ghoramara Island, Mousuni Island, G-Plot, L-Block and some parts of riverside most affected by this cyclone. Kultali (187.254 Sq.km) followed by Kulpi (156.86 Sq.km), Namkhana (198.485 Sq.km) and Basanti (129.53 Sq.km) area under flooded during this cyclone. During COVID-19 pandemic, social distancing is the main problem on cyclone shelter house and relief camp. This area has faced those two disasters at the same time.

Estimation and counter- validation of LISS-III derived leaf area index in Deltaic vegetation

Leaf area index (LAI), a dimensionless biophysical variable is considered as one of the most important factors in characterizing canopy structure. It estimates the amount of foliage area per unit of ground area and helps indirectly to assess biomass and energy balance in an ecosystem. Remote sensing techniques established a strong correlation between the vegetation reflectance characteristics in red and near infra-red bands and LAI. Good number of image derived vegetation indices has been applied so far to estimate LAI successfully. In this paper correlation is established between field-collected LAI and three soil adjusted vegetation indices, i.e., SAVI, MSAVI and OSAVI derived from IRS-LISS-III data in deltaic ecosystem in Sagar Island of West Bengal, India. LAI was estimated from OSAVI for the whole island as OSAVI yielded best result (R2= 0.92). Coarse resolution MODIS LAI (MOD 15A3) product was counter-validated with respect to the LISS-III derived LAI image following the upscale validation approach. Out of the six best-fit models applied, the logistic regression showed strong positive correspondence between the two products (R2 = 0.71). Uncertainty of the model was also assessed and probable reasons were identified.

Comparative Assessment of Livelihood Vulnerability of Climate Induced Migrants: A Micro Level Study on Sagar Island, India

The effects of climate change are causing large scale human displacements over the past few decades. Climate refugees are putting the biggest challenges to the geophysical biological and social system all over the world. This paper attempts to assess and compare the vulnerability of the climate-induced migrants and regular settlers of selected mouzas of Sagar Island, south 24parganas, India. People are witnessing their lands vanishing under their feet in these constantly sinking and shrinking deltaic estuaries of Sundarban. Findings of LVI and LVI-IPCC analysis indicate that the climate-induced migrant communities are more exposed to climatic variability due to the poor adaptive capacity. Moreover, poor access to food, water, health facilities is making them extremely vulnerable with lower resilience as these mouzas are facing frequent flooding, severe coastal erosion, embankment breaching and higher storm surge on annual basis. The outcomes of this study could be beneficial ineffective on-site risk management and planning propositions.