Spatial-Temporal Assessment of Urban Wetlands in Metropolitan Area, India: A Framework for Sustainable Restoration and Management

Spatial-Temporal Assessment of Urban Wetlands in Metropolitan Area, India: A Framework for Sustainable Restoration and Management | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Spatial-Temporal Assessment of Urban Wetlands in Metropolitan Area, India: A Framework for Sustainable Restoration and Management Pankaj Kumar Roy, Shilpa Saha, Arghya Das, Anisha Biswas, Arnab Ghosh, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7495461/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Urban wetlands play a pivotal role in maintaining ecological balance, regulating hydrology, supporting biodiversity, and offering socio-economic benefits. This study presents a comprehensive, multi-tiered framework for assessing wetland distribution, condition, and transformation in Borough-XIII of the Kolkata Municipal Corporation, India. Employing an integrative methodology that combines high-resolution satellite imagery, GIS-based spatial analysis and systematic ground-truthing, the research identifies both historical trends and current site-specific conditions of wetlands across different Wards. The spatial-temporal analysis (2004–2022) reveals contrasting trajectories marked expansion in Wards 115 and 122, and significant shrinkage in Wards 116, 117 and 119 attributable to factors such as urban encroachment and partial restoration. The decadal LULC analysis revealed an 80% decline in waterbodies alongside a 26% increase in built-up areas, highlighting rapid urban encroachment. MNDWI results further confirmed fragmentation and shrinkage of surface water features, underscoring urgent conservation needs. Field condition assessments highlight spatial heterogeneity in water quality, eutrophication, and vegetation cover, with macrophyte dominance signalling nutrient loading and altered ecological states. Site status data point to alarming wetland loss in Wards 119 and 120, while emerging waterbodies in Ward 115 suggest improved detection and potential restoration. Temporal satellite comparisons further confirm ongoing degradation, with wetland disappearance driven primarily by infrastructure development. Scientifically, these findings underscore the fragmented and vulnerable state of urban wetlands and highlight the need for integrated watershed management, policy enforcement and community participation. This study introduces the critical role of spatial monitoring and ground validation in guiding sustainable urban planning and ecological resilience in megacities. Urban Wetlands Wetland Transformation Ground Truthing Ecological Degradation Sustainable Urban Planning Eutrophication Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 1. Introduction Wetlands are a unique ecosystem characterized by the presence of water, either permanent or seasonal, which supports vegetation adapted to saturated soil conditions (Roy et al., 2025). They are among the most productive ecosystems globally, providing essential services such as water purification, flood control, carbon sequestration and biodiversity conservation (McInnes, 2010). In the context of urban environments, these ecosystems play a pivotal role in mitigating the adverse effects of rapid urbanization (Bowen, 2000). However, rapid urbanization has led to significant degradation of these wetlands, with studies indicating a global loss of approximately 50% of wetlands since the 19th century. Urban wetlands have undergone significant transformations due to rapid urbanization, climate change and evolving environmental policies (Ehrenfeld, 2000). Urbanization has led to the encroachment and degradation of wetlands, reducing their ecological functions (Saha et al., 2024a). For instance, studies have documented the loss of wetlands in cities like Lagos, Nigeria, due to unplanned urban growth (Akinbile and Yusoff, 2011). Similarly, in Jakarta, Indonesia, wetland areas have diminished significantly, exacerbating flood risks (Firman et al., 2011). Climate change intensifies the vulnerability of urban wetlands through sea-level rise, altered precipitation patterns and increased temperatures (Paul and Meyer, 2001). In coastal cities like New Orleans, USA, wetlands face threats from both subsidence and rising sea levels, leading to habitat loss and reduced storm protection (Day et al., 2007). Urban wetlands contribute to ecological balance by supporting diverse flora and fauna. Their degradation leads to habitat loss and decreased biodiversity (Khusrul Amin et al., 2013; McInnes, 2010). Additionally, wetlands hold cultural significance for many communities. The loss of these areas can erode cultural identities and traditional practices. The primary driver of wetland transformation in cities is urban expansion. The conversion of wetlands for residential, commercial, and infrastructural development has been documented globally (Furukawa, 2013). In cities like Kolkata, India, the East Kolkata Wetlands have experienced substantial shrinkage due to urban expansion and pollution (Ghosh et al., 2018). Similarly, urban wetlands in Latin America face challenges from land-use changes and infrastructure development, leading to habitat loss and reduced ecosystem services (Pradilla and Hack, 2024). In coastal cities, urbanization has led to substantial wetland loss, compromising biodiversity and ecosystem services. Similarly, in China, rapid urban growth has altered hydrological regimes, affecting wetland ecosystems (Yuehua et al., 2021). The loss of urban wetlands not only diminishes ecological functions but also exacerbates urban challenges such as heat islands, flooding, and reduced air quality (Li et al., 2009; Seto et al., 2012). Recognizing these challenges, initiatives like the Ramsar Convention's "Wetland City" accreditation aim to promote sustainable urban planning that integrates wetland conservation (Gardner and Davidson, 2011). Recent approaches emphasize restoring wetlands to enhance urban resilience. The “Sponge City” concept in China integrates wetlands into urban planning to manage stormwater and mitigate flooding (Yu et al., 2015). Similarly, the Blue-Green Cities framework in Europe promotes the use of wetlands for sustainable urban drainage and biodiversity conservation (Thorne et al., 2018; Kennedy and Buys, 2010). Effective wetland management requires supportive policies and community involvement. In the USA, the Clean Water Act has been instrumental in protecting wetlands, while community-led initiatives in cities like Portland, Oregon, have successfully restored urban wetland areas (Mitsch et al., 2015). Constructed wetlands have emerged as an effective and sustainable alternative to support the restoration of degraded natural wetlands, particularly in urban and peri-urban environments where space and ecological integrity are under constant pressure (Roy et al., 2025; Yang et al. 2021). They are designed to mimic the structure and function of natural wetlands, offering multifaceted benefits in terms of water purification, biodiversity enhancement, flood control and carbon sequestration. (Roy et al., 2025; Saha et al., 2025). As part of an integrated wetland management strategy, constructed wetlands present a scalable, community-inclusive approach to rehabilitate ecosystem functions and support sustainable urban development (Saha et al., 2024b). Recognizing the importance of wetlands, several cities have initiated restoration projects. In Japan, urban wetland restoration has focused on enhancing biodiversity and ecosystem services (Furukawa, 2013). In the United States, rehabilitation efforts prioritize wetland functions over historical vegetation structures to maximize ecological benefits (Spieles, 2005). The transformation of wetlands in the Kolkata Municipal Corporation (KMC) is emblematic of the challenges faced by urban wetlands worldwide. Over the past few decades, the wetlands have faced significant threats due to unplanned urban expansion, illegal encroachments, and infrastructural developments (Mondal et al., 2024). Factors such as land-use changes, pollution and policy gaps have contributed to the degradation of these vital ecosystems (Mondal et al., 2017; Sajor and Ongsakul, 2007). Understanding the dynamics of wetland transformation in KMA is crucial for developing effective conservation strategies and ensuring the sustainability of urban ecosystems. This paper examines the transformation of wetlands in metropolitan cities with special reference to Kolkata Municipal Corporation (KMC), focusing on the impacts of urbanization and the importance of integrating wetland conservation into urban planning. 2. Database and Methodology Wetlands in urban landscapes serve multifaceted ecological, hydrological, and socio-economic roles. An effective framework for analyzing such wetlands should be holistic, integrating physical, biological, chemical, and socio-political dimensions. The following multi-tiered framework is proposed for systematic assessment of wetlands. 2.1 Framework for Analyzing the Wetlands This study employs a systematic approach combining geospatial analysis with ground truthing to evaluate the condition, distribution, and transformation of wetlands in urban landscapes. The framework consists of the following steps (Fig.1.): Initial screening of potential wetlands was conducted using high-resolution satellite imagery on Google Earth. Wetlands were visually identified based on surface water signatures, vegetation patterns and surrounding land use characteristics. Coordinates (latitude and longitude) of each identified wetland were extracted using the in-built coordinate system in Google Earth Pro. These geographic references formed the basis for spatial mapping and ground validation. The extracted coordinates were compiled into KML (Keyhole Markup Language) files for spatial mapping. These files were imported into GIS software (QGIS 3.34.3.) for detailed mapping, overlaying with administrative boundaries, land cover layers and urban infrastructure. Land use land cover maps have been prepared for 2014 and 2024 (using Landsat-8 satellite imagery) for analysing the decadal changes using Google Earth Engine (GEE). A Modified Normalized Difference Water Index (MNDWI) has also been calculated from Sentinel-2 Multi Spectral Instrument (MSI) imagery of 2024 to delineate surface water features and processed using GEE. A series of preprocessing processes was undertaken before the index was calculated. Level-2A surface reflectance products were first chosen to reduce atmospheric influences like scattering and absorption. Cloud-covered scenes were removed by implementing a 20% cloud cover filter, whereas cloud and shadow artifacts were masked using the QA60 band and Sentinel-2 cloud probability data. The imagery was subsequently clipped to the administrative boundary of Borough-XIII to limit the analysis to the study area. All bands were resampled to a common 10m resolution because Sentinel-2 bands are acquired at various spatial resolutions, thus enabling pixel-level analysis consistently. The MNDWI is defined as: Where, the Green band (Band 3; 0.56 µm, 10 m) represents reflectance in the visible green spectrum, and SWIR1 band (Band 11; 1.61 µm, 20 m) represents reflectance in the short-wave infrared region. The choice of these bands is based on the principle that water strongly absorbs SWIR wavelengths but reflects green wavelengths, thereby enhancing the separability of water from surrounding built-up or vegetated areas. The workflow included the following steps: Selection of cloud-free satellite imagery covering Borough-XIII. Pre-processing, including atmospheric correction and image clipping to the municipal boundary. Calculation of the MNDWI index using GEE’s band math functions. Visualization with a colour gradient ranging from -0.4 (non-water features) to +0.4 (open water features). Integration of the results with a base map for spatial interpretation. The MNDWI values that were calculated were classified and mapped using a continuous colour ramp from dark blue (high MNDWI, indicating surface water bodies) to pale yellow (negative values indicating built-up areas and soil). Finally, ground-level surveys were conducted to verify and validate the mapped locations. Each wetland was photo-documented using GPS-enabled cameras to capture both the visual condition and geospatial metadata. This data was crucial for verifying satellite interpretations and establishing ground truth. A qualitative and quantitative assessment of each site was carried out, noting current status, land use pressure, vegetation presence, anthropogenic disturbances, and ecological degradation. The field condition was categorized based on a structured checklist. This integrative methodology enabled comprehensive monitoring of wetland transformation across urban landscapes, supporting both spatial-temporal analysis and site-specific policy interventions. 2.2 Study Area The study was conducted across selected administrative Wards within Borough-XIII of the Kolkata Municipal Corporation (KMC), situated in the southern part of Kolkata, West Bengal, India. Specifically, the focus was on Wards 115, 116, 117, 118, 119, 120 and 122, which encompass a diverse range of urban and peri-urban land uses, including residential neighbourhoods, informal settlements, open spaces, and remnant wetlands. This area, historically rich in waterbodies and low-lying marshlands, has experienced significant anthropogenic transformation over the past decades due to urban expansion, infrastructure development and land reclamation (Haque et al., 2019). The selection of these Wards was based on preliminary satellite assessments indicating visible wetland features, seasonal water retention and evidence of degradation. Geographically, Borough-XIII lies between approximately 22.27°N to 22.31°N latitude and 88.18°E to 88.21°E longitude, bounded by the Eastern Metropolitan Bypass to the east and Tolly’s Nullah canal to the west (Fig.2.). This strategic location places the study sites within the dynamic interface of urban sprawl and environmental transition zones. These Wards were chosen for their representational variability in wetland conditions ranging from relatively intact ponds and marshes to severely degraded and encroached sites (Sarkar, 2004). Field assessments and community-level interactions were also feasible due to accessible road networks and cooperation from local municipal offices, making the selected sites suitable for a detailed wetland transformation analysis. 3. Major Findings The study revealed a drastic decline in wetland and waterbody extent in Borough-XIII, with built-up areas expanding significantly over the past two decades. Spatial and temporal analyses, supported by MNDWI mapping and field surveys, highlight severe ecological degradation, hydrological stress, and loss of urban resilience. 3.1 Spatial Distribution of Wetlands The spatial distribution map of wetlands across Wards 115, 116, 117, 118, 119, 120 and 122 within Borough-XIII of the KMC reveals critical insights into the current status and historical transformations of urban waterbodies. The map distinctly marks existing wetlands (in purple) and disappeared waterbodies (red dots), providing a visual correlation between wetland degradation and urban intensification (Fig.3.). A prominent concentration of wetlands is evident in the southern part of the study area, particularly in Ward 122, which still retains a dense and scattered distribution of waterbodies. However, this region also shows the highest density of disappeared wetlands, suggesting rapid recent transformations due to urban encroachment and unregulated land-use change. Wards 115 and 120 also show a relatively significant number of extant wetlands, albeit interspersed with a substantial presence of lost waterbodies, indicating a transitional phase of degradation. In contrast, northern Wards like 116, 117, 118 and 119 demonstrate a more sparse distribution of surviving wetlands with a relatively high density of vanished ones, highlighting an advanced stage of wetland loss. The clustering of disappeared waterbodies along Ward peripheries and transportation corridors may reflect anthropogenic pressures from real estate expansion and infrastructure development. Scientifically, this spatial heterogeneity underscores a pattern of progressive fragmentation and disappearance of urban wetlands, potentially compromising hydrological functions, biodiversity habitats and climate regulation. The overlay of disappeared and existing waterbodies offers valuable geospatial evidence supporting urgent policy interventions for wetland conservation and sustainable urban planning in KMC. 3.2 Spatio-Temporal Analysis of Wetlands in 2004 and 2022 The spatio-temporal analysis of wetland area dynamics across Wards 115 to 122 of KMC from 2004 (Landsat 5) to 2022 (Landsat 9) reveals distinct patterns of transformation that reflect both anthropogenic pressures and conservation outcomes. The percentage change in wetland area across these wards highlights a mixed trajectory of expansion and shrinkage, suggesting varied land-use practices, ecological interventions, and urban developmental impacts (Fig.4.). Ward 115 demonstrates a significant increase of 56.48% in wetland area from 2004 to 2022. This growth may be attributed to successful environmental revival efforts, such as wetland restoration programs or improved hydrological connectivity. Similarly, Ward 122 exhibits a 39.90% increase, indicating potential benefits of conservation measures or natural regeneration. In contrast, Ward 116 shows a drastic reduction of 53.70%, reflecting a sharp decline in wetland cover. This alarming trend likely results from rapid urban expansion, encroachment, or land-use conversion for infrastructure. Wards 117, 119 and 120 also show declining trends, with reductions of 15.41%, 10.86% and modest gains of 14.73%, respectively. The shrinkage in Wards 117 and 119 could be linked to increasing developmental stress or loss of ecological buffers due to insufficient regulatory enforcement. Ward 118, on the other hand, experienced a 12.74% increase in wetland area, which may reflect marginal rehabilitation efforts or changes in water retention from seasonal or climatic shifts (Fig.5.). The fluctuating trends highlight the need for continuous satellite-based monitoring, ground validation and policy-driven wetland protection. These spatial dynamics are critical for assessing urban ecological resilience and guiding sustainable wetland management strategies in rapidly urbanizing environments like Kolkata (Fig.6.). 3.3 Assessment of Land Use and Land Cover Modification The comparative LULC analysis of Borough-XIII between 2014 and 2024 demonstrates a significant transformation of the urban landscape, highlighting the rapid pace of urbanization and consequent ecological degradation. In 2014, waterbodies occupied a substantial area (275.99 ha), while built-up zones covered the largest proportion (514.87 ha). Vegetation and marshy land were relatively limited but functioned as essential ecological buffers. By 2024, a marked decline in waterbodies (55.10 ha) and vegetation cover is observed, while built-up areas expanded drastically to nearly 649.56 ha. Marshy lands also registered a modest increase, possibly due to seasonal waterlogging and conversion of degraded wetlands (Fig.7.). The spatial-temporal maps confirm that built-up expansion has encroached upon both waterbodies and vegetative zones, particularly in wards 115, 116, 119, and 122. This has led to the fragmentation and shrinkage of smaller ponds and wetlands, reducing their ecological connectivity. The persistence of some marshy lands in the southern sector suggests incomplete conversion processes, but the overall hydrological regime has been severely disrupted. From an environmental perspective, these changes have multiple implications: Hydrological Stress: The loss of waterbodies reduces groundwater recharge potential, increases runoff, and amplifies the risks of urban flooding, especially in low-lying wards. Biodiversity Loss: The decline of vegetation and wetland habitats threatens local flora and fauna, further diminishing ecosystem services. Urban Heat Island Effect: Expansion of impervious built-up surfaces exacerbates surface heating, contributing to rising local temperatures and reduced microclimatic regulation. Socio-Ecological Vulnerability: Disappearance of waterbodies undermines urban resilience by limiting access to ecosystem-based services such as water storage, drainage, and pollution buffering. Overall, the decade-long LULC dynamics reveal a clear trajectory of unsustainable land transformation, where urban growth has occurred at the expense of ecologically sensitive areas. This underscores the urgent need for integrated urban planning, wetland conservation policies, and adoption of nature-based solutions to restore ecological balance and enhance resilience within Borough-XIII of KMC. 3.4 Assessment of Waterbody Dynamics Using MNDWI The Modified Normalized Difference Water Index (MNDWI) was employed to delineate surface water features within Borough-XIII of the KMC. MNDWI enhances open water features by suppressing built-up land, vegetation, and soil noise, making it particularly effective in densely urbanized areas like Kolkata. The index was computed using satellite imagery (sentinel datasets) accessed through Google Earth Engine (GEE). The generated MNDWI map of Borough-XIII highlights the spatial distribution of water bodies and moisture-rich zones within the area. Positive MNDWI values (>0, shaded in dark blue) represent water features such as ponds, canals, and wetlands. These are predominantly concentrated in the southern and central portions of the borough, with a few scattered patches in the north. Negative values (<0, shown in pale yellow) correspond to built-up areas, vegetation, and dry surfaces, which dominate most of the urban landscape (Fig.8.). The map indicates that although Borough-XIII still retains some water bodies, particularly in its southern part, urbanization and land use changes have significantly reduced their areal extent. The relatively fragmented and patchy water signatures suggest that many of these water bodies are either seasonal or heavily encroached. The northern and western sections of the borough are largely urbanized, with negligible open water presence. This analysis underscores the importance of conserving existing water bodies, which are critical for groundwater recharge, urban flood regulation, and ecological balance in Kolkata’s rapidly urbanizing landscape. 3.5 Field Condition of Wetlands The field condition analysis of wetlands across Wards 115 to 122 of KMC reveals significant spatial heterogeneity in water quality and ecological characteristics. Clean water zones are highest in Ward 115 (31.15%) and Ward 118 (28%), suggesting relatively lower anthropogenic disturbances and better hydrological conditions. In contrast, Wards 119 and 120 show lower clean water percentages (16% and 17.95%, respectively), indicating possible degradation due to pollution or eutrophication (Fig.9.). The growth of macrophytes, which can be indicative of nutrient enrichment or reduced water flow, is widespread particularly in Wards 115 (40.98%), 116 (40%) and 122 (40.88%). While macrophytes can support biodiversity, excessive proliferation may signal eutrophic conditions, affecting water quality and aquatic life. This is supported by elevated eutrophication levels in Wards 115 (13.11%) and 117 (16.67%), where excessive nutrients likely stem from untreated sewage or surface runoff. Water pollution appears most acute in Ward 119 (12%) and Ward 120 (7.69%), possibly due to domestic discharge and insufficient drainage infrastructure. Conversely, Wards 118 and 122 report minimal pollution (0% and 0.63%), possibly reflecting better waste management or natural filtration. The presence of non-natural waterbodies, such as artificial ponds or reservoirs, is minimal, with only Ward 119 (4%) and Ward 122 (0.94%) reflecting such instances, indicating predominantly natural water systems across most Wards. Unclassified conditions, denoting either ambiguous field characteristics or data limitations, are remarkably high in Wards 119 (36%), 120 (35.90%) and 117 (27.78%), pointing to the need for further field validation and improved categorization methods (Fig.10.). Overall, the data underscores varying degrees of ecological health and degradation across the Wards, necessitating Ward-specific management strategies, enhanced monitoring and integrated urban wetland planning to sustain ecosystem services. 3.6 Site Status of Wetlands The site status assessment of wetlands across Wards 115 to 122 of the KMC highlights the dynamic and multifaceted transformation of urban waterbodies. The highest percentage of environmental revival is observed in Ward 119 (20%), indicating effective local conservation or natural recovery, while other Wards such as 115 and 122 also show moderate revival (around 10%). Swampy areas, which suggest wetland persistence or degradation, are most prominent in Ward 122 (29.87%) and Ward 119 (16%), potentially due to encroachment or reduced drainage leading to stagnant conditions (Fig.11.). The most alarming trend is the high proportion of disappeared waterbodies, especially in Wards 119 (36%), 120 (30.77%) and 117 (27.78%). This reflects severe anthropogenic pressures such as urban encroachment, infilling, or conversion for infrastructure development. Such loss not only disrupts ecological functions but also impacts urban climate resilience. Interestingly, Ward 115 stands out with a significant proportion (63.93%) of newly identified waterbodies, possibly indicating previously unmapped or misclassified wetlands now recognized through improved mapping and field validation. This highlights the importance of continuous monitoring using tools like GIS and ground surveys. Restricted access is notably high in Ward 118 (16%), limiting both public engagement and environmental assessment. This may be due to privatization or fencing of wetlands, a growing concern in urban landscapes. The large proportion of unspecified sites, particularly in Ward 117 (61.11%) and Ward 116 (41.67%), reflects data gaps or ambiguities in classification, calling for detailed ground-truthing and stakeholder engagement (Fig.12.). A substantial portion of sites remain unspecified across Wards (21–61%), particularly in Ward 117, underscoring the need for comprehensive field validation and documentation. This analysis provides critical insights for targeted wetland restoration and sustainable urban planning. 3.7 Disappeared Waterbodies The temporal satellite imagery presented for different Wards of KMC demonstrates notable land cover changes in wetland areas over the past decade. These images, captured at various time intervals, provide evidence of dynamic transformations primarily driven by urban expansion and anthropogenic interventions. In Ward 117, the wetland area visible in 2011 is gradually encroached upon by built-up structures by 2018, with a further reduction in waterbody clarity observed in 2022. This indicates progressive land-use change and possible illegal infill for development purposes. Similarly, in Ward 119, between 2015 and 2022, substantial urbanization is evident, where once open or vegetated wetland patches have been converted into dense built environments, likely affecting the ecological functioning and groundwater recharge capacity. Contrastingly, Ward 115 reflects some degree of stabilization or partial restoration. From 2015 to 2021, although development surrounds the waterbody, the central wetland area remains mostly intact, possibly due to planning regulations or local conservation initiatives. In Ward 122, the wetland witnessed in 2011 appears increasingly fragmented and encroached by 2022, signifying intensified land-use pressure in a highly urbanized zone (Fig.13.). These temporal visual analyses underscore the urgent need for stronger wetland protection policies, regular monitoring using high-resolution remote sensing data and community engagement. Without strategic planning and enforcement, such transformations may lead to irreversible loss of urban wetland ecosystems, thereby compromising urban climate resilience, biodiversity, and public health in megacities like Kolkata. The findings underscore the urgent need for integrated, science-based urban wetland management. A combination of policy reforms, improved land-use planning and public engagement is essential to halt degradation and restore ecological functionality. 4. Discussion Urban wetlands play a crucial role in maintaining ecological balance, supporting biodiversity, and offering ecosystem services such as flood regulation and water purification. However, rapid urbanization and unplanned development have led to the degradation, encroachment, and transformation of these fragile ecosystems. The following case studies underline the scale of urban wetland transformation worldwide, often driven by land-use change, infrastructure development and poor governance. However, innovative urban planning, community engagement and green infrastructure solutions demonstrate potential for restoring and integrating wetlands into cityscapes (Table.1.). Table. 1. Global Scale of Urban Wetland Transformation Investigated Regions Threats to Wetlands Proposed Interventions / Restoration Approaches References Rio de Janeiro, Brazil Wetland loss in low-income peri-urban areas increased vulnerability to flooding and disease Integrating wetlands into favelas through participatory design and water-sensitive urban design Herrera (2024) Bangkok, Thailand Wetland transformations under rising urban water demand and land conversion Community-based restoration initiatives in restoring hydrological functions and improving resilience Palakhamarn and Kamolvej (2024) Bogotá, Colombia Lost over 80% of its original wetland coverage due to housing development City-led restoration efforts (jaboque and la conejera wetlands) showed ecological improvement Pradilla and Hack (2024) London, UK Analyzed shift from neglected wetlands to multifunctional green spaces Lea valley wetland restoration project Mell (2022) Addis Ababa, Ethiopia Degradation of wetlands due to solid waste dumping and settlement encroachments Community-based rehabilitation projects showed success in reviving native vegetation and improving water flow regulation Soboka and Gemechu (2021) Shanghai, China Investigated the transformation of wetlands Transformation of wetlands under the “sponge city” initiative Constructed wetlands were used to mitigate urban runoff and restore lost functions in urban ecosystems Wu et al. (2019) Manila, Philippines Urban expansion, industrial discharge, and reclamation projects caused dramatic wetland loss Las piñas-parañaque critical habitat established to protect migratory bird habitats and restore hydrological balance Mercado (2018) Mumbai, India Transformation of mangrove wetlands due to urban expansion and illegal encroachments Neglect of wetland ecosystems worsened flood risks and disrupted coastal biodiversity Advocating for mangrove restoration. Gupta et al. (2017) Toronto, Canada Wetland degradation due to rapid suburban expansion New policy instruments, such as wetland offsetting and urban green space zoning Sizo et al. (2015) Jakarta, Indonesia Wetland loss due to land reclamation and population pressures Decreased wetland area exacerbated flooding and deteriorated water quality Urging for sustainable urban planning and wetland buffer zones Firman et al. (2011) Cape Town, South Africa Transformation of seasonal wetlands and fynbos-dominated ecosystems due to urban expansion Need for biodiversity corridors and ecological infrastructure planning Rebelo et al. (2011) Seoul, South Korea Investigated the Cheonggyecheon Stream restoration, which replaced a buried watercourse with a constructed wetland corridor Revived ecosystem services, improved urban cooling and enhanced public awareness of urban ecology, serving as a global model Cho (2010) New Orleans, USA Wetland degradation exacerbated by levee systems and development Increased vulnerability to storm surges Emphasizing the urgency of wetland restoration Day et al. (2007) New York, USA Wetland conversion driven by real estate expansion and infrastructure development Fragmentation and biodiversity loss Policies like the clean water act helped reverse some degradation Bolund and Hunhammar (1999) Source: Data compiled by the authors The transformation of wetlands in the KMC is emblematic of the challenges faced by urban wetlands worldwide. Factors such as land-use changes, pollution and policy gaps have contributed to the degradation of these vital ecosystems. Understanding the dynamics of wetland transformation in KMC is crucial for developing effective conservation strategies and ensuring the sustainability of urban ecosystems. The following discussion draws upon photographic evidence collected through field surveys across selected Wards (115 to 122) of the KMC. By visually documenting and categorizing various wetland conditions and site statuses, the analysis provides critical insights into the environmental health, anthropogenic pressures, and transitional dynamics of these urban waterbodies. These observations offer a grounded understanding of the spatial and ecological diversity of wetland systems, supporting more effective planning and conservation strategies. Photographic evidence of clean water conditions (e.g., in Wards 119 and 117) reflects relatively undisturbed waterbodies with low turbidity and high light penetration, often indicative of minimal nutrient load and active hydrological functioning. Conversely, growth of macrophytes in some Wards (e.g., in Wards 115 and 118) is a clear sign of nutrient enrichment, likely due to domestic runoff or untreated greywater discharge. Macrophyte proliferation, while providing temporary oxygenation and habitat, eventually leads to biomass decay, further fuelling eutrophication. Marshland conditions, visible in Wards 115 and 116, show dense, emergent vegetation, indicating stagnant water with low depth and organic-rich sedimentation, an advanced phase of natural wetland succession. Meanwhile, the presence of eutrophication (noted in Ward 117), with green algal blooms and surface scum, points toWard excessive nitrogen and phosphorus input, often linked to fertilizer leaching and sewage influx. water pollution conditions (Wards 115 and 120) display litter accumulation and solid waste deposition, revealing direct anthropogenic interference and ineffective waste management systems. The non-natural waterbody classification (e.g., in Ward 122) depicts encroached or artificially modified water systems embedded within dense urban structures, often functioning more as drainage units than ecological wetlands. unclassified sites, such as in Wards 117 and 120, suggest ambiguous or transitioning landscapes possibly undergoing rapid alteration (Fig.14.). Site statuses such as environmental revival in Wards 118 and 122 illustrates notable community or municipal restoration efforts, visible through cleaner water and active vegetation regeneration. In contrast, swampy areas in Wards 119 and 122 are marked by semi-aquatic, poorly drained regions potentially transitioning into marshland. Disappeared waterbodies (Wards 115 and 118) are especially concerning, revealing either complete infilling, infrastructure development, or seasonal desiccation, a direct outcome of urban expansion or altered catchment hydrology. Sites classified as newly identified (Wards 115 and 122) are particularly significant as they suggest previously unmapped or overlooked waterbodies, now discernible due to field validation or seasonal variation. Restricted access in Wards 117 and 120 poses methodological limitations, emphasizing the importance of community engagement and administrative support in comprehensive mapping. Finally, unspecified statuses, such as in Wards 116 and 118, highlight data gaps, either due to field ambiguity or temporal variability, warranting continuous monitoring (Fig.15.). This photographic dataset reinforces the necessity of integrated field and geospatial assessments in urban wetland studies. It also underscores the spatial variability and pressing threats these ecosystems face within metropolitan contexts, urging for proactive governance and community-led conservation measures. Despite progress, challenges such as land-use conflicts, funding limitations and governance issues persist. Future research should focus on developing integrated management strategies that balance urban development with wetland conservation, considering socio-economic and ecological factors. Efforts must include routine monitoring, expansion of green infrastructure, protection of hydrological connectivity and incentivization of community-based conservation models. Constructed wetlands can serve as a complementary solution especially in areas where natural restoration is unfeasible due to irreversible land-use changes. As part of an integrated wetland management strategy, they present a scalable, community-inclusive approach to rehabilitate ecosystem functions and support sustainable urban development. 5. Conclusion The integrated field-based and spatial assessment of wetland ecosystems across Wards 115 to 122 in KMC reveals a dynamic and multifaceted landscape shaped by both natural processes and anthropogenic pressures. The temporal analysis of wetland area from 2004 to 2022 across selected Wards of KMC, reveals contrasting trends in spatial transformation. Significant area expansion is observed in Ward 115 and Ward 122, potentially indicating improved mapping accuracy, seasonal variation, or restoration interventions. Conversely, Wards 116 and 117 exhibit a sharp decline, especially Ward 116, which saw over 50% reduction, suggesting encroachment or land-use conversion. The LULC assessments reveal a sharp decline in ecologically sensitive areas within Borough-XIII over the past decade. Waterbodies, which covered approximately 275.99 ha in 2014, have been reduced drastically to only 55.10 ha in 2024, reflecting a loss of nearly 80% of their original extent. Similarly, vegetation cover has also diminished, while built-up areas expanded from 514.87 ha to 649.56 ha, marking an increase of over 26%. This spatial transformation indicates that urban growth has primarily occurred at the expense of wetlands and vegetative buffers. The MNDWI analysis further highlights fragmentation and encroachment of surface water bodies, particularly in the northern and western wards, where open water features have almost disappeared. Such changes have disrupted the hydrological regime, reduced groundwater recharge potential, and heightened urban flood risks. Moreover, the decline in green and blue spaces exacerbates biodiversity loss, weakens ecosystem service provision, and contributes to the intensification of the warming effects. The method was extremely effective for hydrological study in urban areas since the MNDWI can effectively remove the urban spectral noise, yielding valuable information for the exploration of flood hazard, wetland conservation, and sustainable water resource management in the rapidly developing context of Kolkata. The photographic documentation, in conjunction with temporal land cover data, provides a robust foundation for understanding the evolving conditions and transformation trajectories of these urban wetlands. While certain Wards demonstrate signs of environmental revival and increased waterbody area, potentially due to better monitoring or restoration initiatives others suffer from rapid shrinkage, disappearance, or encroachment, indicating critical threats to wetland sustainability. The field condition assessment reveals heterogeneous wetland characteristics. The widespread growth of macrophytes, particularly in Wards 115 and 122 (both above 40%), reflects nutrient enrichment and potential eutrophic conditions. Pollution levels are relatively low overall, peaking at 12% in Ward 119. The site status data across the Wards highlight varied stages of wetland transformation and management challenges. The highest proportion of environmentally revived sites is in Ward 119 (20%), indicating successful ecological interventions. Swampy areas are most prevalent in Ward 122 (29.87%), suggesting retained natural wetland characteristics. Alarmingly, a significant percentage of waterbodies have disappeared, especially in Wards 119 and 120 (36% and 30.77%, respectively), pointing to rapid urban encroachment and land use change. Recognizing wetlands as multifunctional assets in terms of biodiversity, climate regulation and social well-being is crucial for shaping resilient, sustainable urban futures. Collaborative efforts between governments, agencies, and communities are vital in addressing flood resilience and ensuring the sustainability of urban wetlands. Ultimately, preserving Kolkata’s wetlands is not only an environmental imperative but also a foundational step toward achieving equitable and climate-adaptive urban development. Declarations Disclosure of Potential Conflicts of Interest The authors declare that they have no potential conflicts of interest. Informed Consent Not applicable. Funding The authors declare that no funds, grants, or other forms of support were received during the preparation of this manuscript. Financial support was provided solely during the execution phase of the project and not during the manuscript drafting stage. Author Contribution Author P.K.R. contributed to the study conception. The methodology and design of the study were contributed by Shilpa Saha. Data collection was performed by S.S., A.B., and A.N. Material preparation, formal analysis and investigation were performed by S.S. and A.B. The first draft of the main manuscript was written by S.S. P.K.R. reviewed the manuscript. Other contributions given by A.D., A.G., and P.R. All authors approved the final manuscript. Acknowledgement The authors gratefully acknowledge the Kolkata Municipal Corporation (KMC) for providing financial support for the project titled “Preparation of an Inventory of Waterbodies by Executing Ground Verification of NRSA (Aerial) Map and Its Correlation with the KMC Tank List”, covering Wards 101 to 144 of the KMC. This paper forms a part of the broader scope of this project. The authors also extend their sincere thanks to the Environment and Heritage Department, KMC, for their valuable assistance in facilitating the smooth execution of the research. Gratitude is further expressed to the residents of Borough-XIII of KMC for offering the necessary information and support critical to the successful completion of this study. References Akinbile, C. O., and Yusoff, M. S. (2011). Environmental impact of leachate pollution on groundwater supplies in Akure, Nigeria. International Journal of Environmental Science and Development , 2 (1), 81. Bolund, P., and Hunhammar, S. (1999). 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Geology in China , 48 (5), 1305-1333. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7495461","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":509890086,"identity":"da0701e6-cd64-49f8-8447-a6c0ffc169ab","order_by":0,"name":"Pankaj Kumar 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Introduction","content":"\u003cp\u003eWetlands are a unique ecosystem characterized by the presence of water, either permanent or seasonal, which supports vegetation adapted to saturated soil conditions (Roy et al., 2025). They are among the most productive ecosystems globally, providing essential services such as water purification, flood control, carbon sequestration and biodiversity conservation (McInnes, 2010). In the context of urban environments, these ecosystems play a pivotal role in mitigating the adverse effects of rapid urbanization (Bowen, 2000). However, rapid urbanization has led to significant degradation of these wetlands, with studies indicating a global loss of approximately 50% of wetlands since the 19th century.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eUrban wetlands have undergone significant transformations due to rapid urbanization, climate change and evolving environmental policies (Ehrenfeld, 2000). Urbanization has led to the encroachment and degradation of wetlands, reducing their ecological functions (Saha et al., 2024a). For instance, studies have documented the loss of wetlands in cities like Lagos, Nigeria, due to unplanned urban growth (Akinbile and Yusoff, 2011). Similarly, in Jakarta, Indonesia, wetland areas have diminished significantly, exacerbating flood risks (Firman et al., 2011). Climate change intensifies the vulnerability of urban wetlands through sea-level rise, altered precipitation patterns and increased temperatures (Paul and Meyer, 2001). In coastal cities like New Orleans, USA, wetlands face threats from both subsidence and rising sea levels, leading to habitat loss and reduced storm protection (Day et al., 2007).\u003c/p\u003e\n\u003cp\u003eUrban wetlands contribute to ecological balance by supporting diverse flora and fauna. Their degradation leads to habitat loss and decreased biodiversity (Khusrul Amin et al., 2013; McInnes, 2010). Additionally, wetlands hold cultural significance for many communities. The loss of these areas can erode cultural identities and traditional practices. The primary driver of wetland transformation in cities is urban expansion. The conversion of wetlands for residential, commercial, and infrastructural development has been documented globally (Furukawa, 2013). In cities like Kolkata, India, the East Kolkata Wetlands have experienced substantial shrinkage due to urban expansion and pollution (Ghosh et al., 2018). Similarly, urban wetlands in Latin America face challenges from land-use changes and infrastructure development, leading to habitat loss and reduced ecosystem services (Pradilla and Hack, 2024). In coastal cities, urbanization has led to substantial wetland loss, compromising biodiversity and ecosystem services. Similarly, in China, rapid urban growth has altered hydrological regimes, affecting wetland ecosystems (Yuehua et al., 2021).\u003c/p\u003e\n\u003cp\u003eThe loss of urban wetlands not only diminishes ecological functions but also exacerbates urban challenges such as heat islands, flooding, and reduced air quality (Li et al., 2009; Seto et al., 2012). Recognizing these challenges, initiatives like the Ramsar Convention\u0026apos;s \u0026quot;Wetland City\u0026quot; accreditation aim to promote sustainable urban planning that integrates wetland conservation (Gardner and Davidson, 2011). Recent approaches emphasize restoring wetlands to enhance urban resilience. The \u0026ldquo;Sponge City\u0026rdquo; concept in China integrates wetlands into urban planning to manage stormwater and mitigate flooding (Yu et al., 2015). Similarly, the Blue-Green Cities framework in Europe promotes the use of wetlands for sustainable urban drainage and biodiversity conservation (Thorne et al., 2018; Kennedy and Buys, 2010).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEffective wetland management requires supportive policies and community involvement. In the USA, the Clean Water Act has been instrumental in protecting wetlands, while community-led initiatives in cities like Portland, Oregon, have successfully restored urban wetland areas (Mitsch et al., 2015). Constructed wetlands have emerged as an effective and sustainable alternative to support the restoration of degraded natural wetlands, particularly in urban and peri-urban environments where space and ecological integrity are under constant pressure (Roy et al., 2025;\u0026nbsp;Yang et al. 2021). They are designed to mimic the structure and function of natural wetlands, offering multifaceted benefits in terms of water purification, biodiversity enhancement, flood control and carbon sequestration. (Roy et al., 2025;\u0026nbsp;Saha et al., 2025). As part of an integrated wetland management strategy, constructed wetlands present a scalable, community-inclusive approach to rehabilitate ecosystem functions and support sustainable urban development\u0026nbsp;(Saha et al., 2024b). Recognizing the importance of wetlands, several cities have initiated restoration projects. In Japan, urban wetland restoration has focused on enhancing biodiversity and ecosystem services (Furukawa, 2013). In the United States, rehabilitation efforts prioritize wetland functions over historical vegetation structures to maximize ecological benefits (Spieles, 2005).\u003c/p\u003e\n\u003cp\u003eThe transformation of wetlands in the Kolkata Municipal Corporation (KMC) is emblematic of the challenges faced by urban wetlands worldwide. Over the past few decades, the wetlands have faced significant threats due to unplanned urban expansion, illegal encroachments, and infrastructural developments (Mondal et al., 2024). Factors such as land-use changes, pollution and policy gaps have contributed to the degradation of these vital ecosystems (Mondal et al., 2017;\u0026nbsp;Sajor and Ongsakul, 2007). Understanding the dynamics of wetland transformation in KMA is crucial for developing effective conservation strategies and ensuring the sustainability of urban ecosystems.\u003c/p\u003e\n\u003cp\u003eThis paper examines the transformation of wetlands in metropolitan cities with special reference to Kolkata Municipal Corporation (KMC), focusing on the impacts of urbanization and the importance of integrating wetland conservation into urban planning.\u0026nbsp;\u003c/p\u003e"},{"header":"2.\tDatabase and Methodology","content":"\u003cp\u003eWetlands in urban landscapes serve multifaceted ecological, hydrological, and socio-economic roles. An effective framework for analyzing such wetlands should be holistic, integrating physical, biological, chemical, and socio-political dimensions. The following multi-tiered framework is proposed for systematic assessment of wetlands.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.1 Framework for Analyzing the Wetlands\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study employs a systematic approach combining geospatial analysis with ground truthing to evaluate the condition, distribution, and transformation of wetlands in urban landscapes. The framework consists of the following steps (Fig.1.):\u003c/p\u003e\n\u003cp\u003eInitial screening of potential wetlands was conducted using high-resolution satellite imagery on Google Earth. Wetlands were visually identified based on surface water signatures, vegetation patterns and surrounding land use characteristics. Coordinates (latitude and longitude) of each identified wetland were extracted using the in-built coordinate system in Google Earth Pro. These geographic references formed the basis for spatial mapping and ground validation. The extracted coordinates were compiled into KML (Keyhole Markup Language) files for spatial mapping. These files were imported into GIS software (QGIS 3.34.3.) for detailed mapping, overlaying with administrative boundaries, land cover layers and urban infrastructure.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eLand use land cover maps have been prepared for 2014 and 2024 (using Landsat-8 satellite imagery) for analysing the decadal changes using Google Earth Engine (GEE). A Modified Normalized Difference Water Index (MNDWI) has also been calculated from Sentinel-2 Multi Spectral Instrument (MSI) imagery of 2024 to delineate surface water features and processed using GEE. A series of preprocessing processes was undertaken before the index was calculated. Level-2A surface reflectance products were first chosen to reduce atmospheric influences like scattering and absorption. Cloud-covered scenes were removed by implementing a 20% cloud cover filter, whereas cloud and shadow artifacts were masked using the QA60 band and Sentinel-2 cloud probability data. The imagery was subsequently clipped to the administrative boundary of Borough-XIII to limit the analysis to the study area. All bands were resampled to a common 10m resolution because Sentinel-2 bands are acquired at various spatial resolutions, thus enabling pixel-level analysis consistently.\u003c/p\u003e\n\u003cp\u003eThe MNDWI is defined as:\u003c/p\u003e\n\u003cp\u003e\u003cimg 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\" width=\"319\" height=\"93\"\u003e\u003c/p\u003e\n\u003cp\u003eWhere, the Green band (Band 3; 0.56 \u0026micro;m, 10 m) represents reflectance in the visible green spectrum, and SWIR1 band (Band 11; 1.61 \u0026micro;m, 20 m) represents reflectance in the short-wave infrared region. The choice of these bands is based on the principle that water strongly absorbs SWIR wavelengths but reflects green wavelengths, thereby enhancing the separability of water from surrounding built-up or vegetated areas.\u003c/p\u003e\n\u003cp\u003eThe workflow included the following steps:\u003c/p\u003e\n\u003cul class=\"decimal_type\"\u003e\n \u003cli\u003eSelection of cloud-free satellite imagery covering Borough-XIII.\u003c/li\u003e\n \u003cli\u003ePre-processing, including atmospheric correction and image clipping to the municipal boundary.\u003c/li\u003e\n \u003cli\u003eCalculation of the MNDWI index using GEE\u0026rsquo;s band math functions.\u003c/li\u003e\n \u003cli\u003eVisualization with a colour gradient ranging from -0.4 (non-water features) to +0.4 (open water features).\u003c/li\u003e\n \u003cli\u003eIntegration of the results with a base map for spatial interpretation.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThe MNDWI values that were calculated were classified and mapped using a continuous colour ramp from dark blue (high MNDWI, indicating surface water bodies) to pale yellow (negative values indicating built-up areas and soil).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFinally, ground-level surveys were conducted to verify and validate the mapped locations. Each wetland was photo-documented using GPS-enabled cameras to capture both the visual condition and geospatial metadata. This data was crucial for verifying satellite interpretations and establishing ground truth. A qualitative and quantitative assessment of each site was carried out, noting current status, land use pressure, vegetation presence, anthropogenic disturbances, and ecological degradation. The field condition was categorized based on a structured checklist.\u003c/p\u003e\n\u003cp\u003eThis integrative methodology enabled comprehensive monitoring of wetland transformation across urban landscapes, supporting both spatial-temporal analysis and site-specific policy interventions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.2 Study Area\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was conducted across selected administrative Wards within Borough-XIII of the Kolkata Municipal Corporation (KMC), situated in the southern part of Kolkata, West Bengal, India. Specifically, the focus was on Wards 115, 116, 117, 118, 119, 120 and 122, which encompass a diverse range of urban and peri-urban land uses, including residential neighbourhoods, informal settlements, open spaces, and remnant wetlands. This area, historically rich in waterbodies and low-lying marshlands, has experienced significant anthropogenic transformation over the past decades due to urban expansion, infrastructure development and land reclamation (Haque et al., 2019). The selection of these Wards was based on preliminary satellite assessments indicating visible wetland features, seasonal water retention and evidence of degradation.\u003c/p\u003e\n\u003cp\u003eGeographically, Borough-XIII lies between approximately 22.27\u0026deg;N to 22.31\u0026deg;N latitude and 88.18\u0026deg;E to 88.21\u0026deg;E longitude, bounded by the Eastern Metropolitan Bypass to the east and Tolly\u0026rsquo;s Nullah canal to the west (Fig.2.). This strategic location places the study sites within the dynamic interface of urban sprawl and environmental transition zones. These Wards were chosen for their representational variability in wetland conditions ranging from relatively intact ponds and marshes to severely degraded and encroached sites (Sarkar, 2004). Field assessments and community-level interactions were also feasible due to accessible road networks and cooperation from local municipal offices, making the selected sites suitable for a detailed wetland transformation analysis.\u003c/p\u003e"},{"header":"3.\tMajor Findings","content":"\u003cp\u003eThe study revealed a drastic decline in wetland and waterbody extent in Borough-XIII, with built-up areas expanding significantly over the past two decades. Spatial and temporal analyses, supported by MNDWI mapping and field surveys, highlight severe ecological degradation, hydrological stress, and loss of urban resilience.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.1 Spatial Distribution of Wetlands\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe spatial distribution map of wetlands across Wards 115, 116, 117, 118, 119, 120 and 122 within Borough-XIII of the KMC reveals critical insights into the current status and historical transformations of urban waterbodies. The map distinctly marks existing wetlands (in purple) and disappeared waterbodies (red dots), providing a visual correlation between wetland degradation and urban intensification (Fig.3.).\u003c/p\u003e\n\u003cp\u003eA prominent concentration of wetlands is evident in the southern part of the study area, particularly in Ward 122, which still retains a dense and scattered distribution of waterbodies. However, this region also shows the highest density of disappeared wetlands, suggesting rapid recent transformations due to urban encroachment and unregulated land-use change. Wards 115 and 120 also show a relatively significant number of extant wetlands, albeit interspersed with a substantial presence of lost waterbodies, indicating a transitional phase of degradation.\u003c/p\u003e\n\u003cp\u003eIn contrast, northern Wards like 116, 117, 118 and 119 demonstrate a more sparse distribution of surviving wetlands with a relatively high density of vanished ones, highlighting an advanced stage of wetland loss. The clustering of disappeared waterbodies along Ward peripheries and transportation corridors may reflect anthropogenic pressures from real estate expansion and infrastructure development.\u003c/p\u003e\n\u003cp\u003eScientifically, this spatial heterogeneity underscores a pattern of progressive fragmentation and disappearance of urban wetlands, potentially compromising hydrological functions, biodiversity habitats and climate regulation. The overlay of disappeared and existing waterbodies offers valuable geospatial evidence supporting urgent policy interventions for wetland conservation and sustainable urban planning in KMC.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.2 Spatio-Temporal Analysis of Wetlands in 2004 and 2022\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe spatio-temporal analysis of wetland area dynamics across Wards 115 to 122 of KMC from 2004 (Landsat 5) to 2022 (Landsat 9) reveals distinct patterns of transformation that reflect both anthropogenic pressures and conservation outcomes. The percentage change in wetland area across these wards highlights a mixed trajectory of expansion and shrinkage, suggesting varied land-use practices, ecological interventions, and urban developmental impacts (Fig.4.).\u003c/p\u003e\n\u003cp\u003eWard 115 demonstrates a significant increase of 56.48% in wetland area from 2004 to 2022. This growth may be attributed to successful environmental revival efforts, such as wetland restoration programs or improved hydrological connectivity. Similarly, Ward 122 exhibits a 39.90% increase, indicating potential benefits of conservation measures or natural regeneration.\u003c/p\u003e\n\u003cp\u003eIn contrast, Ward 116 shows a drastic reduction of 53.70%, reflecting a sharp decline in wetland cover. This alarming trend likely results from rapid urban expansion, encroachment, or land-use conversion for infrastructure. Wards 117, 119 and 120 also show declining trends, with reductions of 15.41%, 10.86% and modest gains of 14.73%, respectively. The shrinkage in Wards 117 and 119 could be linked to increasing developmental stress or loss of ecological buffers due to insufficient regulatory enforcement. Ward 118, on the other hand, experienced a 12.74% increase in wetland area, which may reflect marginal rehabilitation efforts or changes in water retention from seasonal or climatic shifts (Fig.5.).\u003c/p\u003e\n\u003cp\u003eThe fluctuating trends highlight the need for continuous satellite-based monitoring, ground validation and policy-driven wetland protection. These spatial dynamics are critical for assessing urban ecological resilience and guiding sustainable wetland management strategies in rapidly urbanizing environments like Kolkata (Fig.6.).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.3 Assessment of Land Use and Land Cover Modification\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe comparative LULC analysis of Borough-XIII between 2014 and 2024 demonstrates a significant transformation of the urban landscape, highlighting the rapid pace of urbanization and consequent ecological degradation.\u003c/p\u003e\n\u003cp\u003eIn 2014, waterbodies occupied a substantial area (275.99 ha), while built-up zones covered the largest proportion (514.87 ha). Vegetation and marshy land were relatively limited but functioned as essential ecological buffers. By 2024, a marked decline in waterbodies (55.10 ha) and vegetation cover is observed, while built-up areas expanded drastically to nearly 649.56 ha. Marshy lands also registered a modest increase, possibly due to seasonal waterlogging and conversion of degraded wetlands (Fig.7.).\u003c/p\u003e\n\u003cp\u003eThe spatial-temporal maps confirm that built-up expansion has encroached upon both waterbodies and vegetative zones, particularly in wards 115, 116, 119, and 122. This has led to the fragmentation and shrinkage of smaller ponds and wetlands, reducing their ecological connectivity. The persistence of some marshy lands in the southern sector suggests incomplete conversion processes, but the overall hydrological regime has been severely disrupted.\u003c/p\u003e\n\u003cp\u003eFrom an environmental perspective, these changes have multiple implications:\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003eHydrological Stress:\u003c/strong\u003e The loss of waterbodies reduces groundwater recharge potential, increases runoff, and amplifies the risks of urban flooding, especially in low-lying wards.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eBiodiversity Loss:\u003c/strong\u003e The decline of vegetation and wetland habitats threatens local flora and fauna, further diminishing ecosystem services.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eUrban Heat Island Effect:\u003c/strong\u003e Expansion of impervious built-up surfaces exacerbates surface heating, contributing to rising local temperatures and reduced microclimatic regulation.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eSocio-Ecological Vulnerability:\u003c/strong\u003e Disappearance of waterbodies undermines urban resilience by limiting access to ecosystem-based services such as water storage, drainage, and pollution buffering.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eOverall, the decade-long LULC dynamics reveal a clear trajectory of unsustainable land transformation, where urban growth has occurred at the expense of ecologically sensitive areas. This underscores the urgent need for integrated urban planning, wetland conservation policies, and adoption of nature-based solutions to restore ecological balance and enhance resilience within Borough-XIII of KMC.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.4 Assessment of Waterbody Dynamics Using MNDWI\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Modified Normalized Difference Water Index (MNDWI) was employed to delineate surface water features within Borough-XIII of the KMC. MNDWI enhances open water features by suppressing built-up land, vegetation, and soil noise, making it particularly effective in densely urbanized areas like Kolkata. The index was computed using satellite imagery (sentinel datasets) accessed through Google Earth Engine (GEE).\u003c/p\u003e\n\u003cp\u003eThe generated MNDWI map of Borough-XIII highlights the spatial distribution of water bodies and moisture-rich zones within the area. Positive MNDWI values (\u0026gt;0, shaded in dark blue) represent water features such as ponds, canals, and wetlands. These are predominantly concentrated in the southern and central portions of the borough, with a few scattered patches in the north. Negative values (\u0026lt;0, shown in pale yellow) correspond to built-up areas, vegetation, and dry surfaces, which dominate most of the urban landscape (Fig.8.).\u003c/p\u003e\n\u003cp\u003eThe map indicates that although Borough-XIII still retains some water bodies, particularly in its southern part, urbanization and land use changes have significantly reduced their areal extent. The relatively fragmented and patchy water signatures suggest that many of these water bodies are either seasonal or heavily encroached. The northern and western sections of the borough are largely urbanized, with negligible open water presence. This analysis underscores the importance of conserving existing water bodies, which are critical for groundwater recharge, urban flood regulation, and ecological balance in Kolkata\u0026rsquo;s rapidly urbanizing landscape.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.5 Field Condition of Wetlands\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe field condition analysis of wetlands across Wards 115 to 122 of KMC reveals significant spatial heterogeneity in water quality and ecological characteristics. Clean water zones are highest in Ward 115 (31.15%) and Ward 118 (28%), suggesting relatively lower anthropogenic disturbances and better hydrological conditions. In contrast, Wards 119 and 120 show lower clean water percentages (16% and 17.95%, respectively), indicating possible degradation due to pollution or eutrophication (Fig.9.).\u003c/p\u003e\n\u003cp\u003eThe growth of macrophytes, which can be indicative of nutrient enrichment or reduced water flow, is widespread particularly in Wards 115 (40.98%), 116 (40%) and 122 (40.88%). While macrophytes can support biodiversity, excessive proliferation may signal eutrophic conditions, affecting water quality and aquatic life. This is supported by elevated eutrophication levels in Wards 115 (13.11%) and 117 (16.67%), where excessive nutrients likely stem from untreated sewage or surface runoff.\u003c/p\u003e\n\u003cp\u003eWater pollution appears most acute in Ward 119 (12%) and Ward 120 (7.69%), possibly due to domestic discharge and insufficient drainage infrastructure. Conversely, Wards 118 and 122 report minimal pollution (0% and 0.63%), possibly reflecting better waste management or natural filtration. The presence of non-natural waterbodies, such as artificial ponds or reservoirs, is minimal, with only Ward 119 (4%) and Ward 122 (0.94%) reflecting such instances, indicating predominantly natural water systems across most Wards. Unclassified conditions, denoting either ambiguous field characteristics or data limitations, are remarkably high in Wards 119 (36%), 120 (35.90%) and 117 (27.78%), pointing to the need for further field validation and improved categorization methods (Fig.10.).\u003c/p\u003e\n\u003cp\u003eOverall, the data underscores varying degrees of ecological health and degradation across the Wards, necessitating Ward-specific management strategies, enhanced monitoring and integrated urban wetland planning to sustain ecosystem services.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.6 Site Status of Wetlands\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe site status assessment of wetlands across Wards 115 to 122 of the KMC highlights the dynamic and multifaceted transformation of urban waterbodies. The highest percentage of environmental revival is observed in Ward 119 (20%), indicating effective local conservation or natural recovery, while other Wards such as 115 and 122 also show moderate revival (around 10%). Swampy areas, which suggest wetland persistence or degradation, are most prominent in Ward 122 (29.87%) and Ward 119 (16%), potentially due to encroachment or reduced drainage leading to stagnant conditions (Fig.11.).\u003c/p\u003e\n\u003cp\u003eThe most alarming trend is the high proportion of disappeared waterbodies, especially in Wards 119 (36%), 120 (30.77%) and 117 (27.78%). This reflects severe anthropogenic pressures such as urban encroachment, infilling, or conversion for infrastructure development. Such loss not only disrupts ecological functions but also impacts urban climate resilience. Interestingly, Ward 115 stands out with a significant proportion (63.93%) of newly identified waterbodies, possibly indicating previously unmapped or misclassified wetlands now recognized through improved mapping and field validation. This highlights the importance of continuous monitoring using tools like GIS and ground surveys.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eRestricted access is notably high in Ward 118 (16%), limiting both public engagement and environmental assessment. This may be due to privatization or fencing of wetlands, a growing concern in urban landscapes. The large proportion of unspecified sites, particularly in Ward 117 (61.11%) and Ward 116 (41.67%), reflects data gaps or ambiguities in classification, calling for detailed ground-truthing and stakeholder engagement (Fig.12.).\u003c/p\u003e\n\u003cp\u003eA substantial portion of sites remain unspecified across Wards (21\u0026ndash;61%), particularly in Ward 117, underscoring the need for comprehensive field validation and documentation. This analysis provides critical insights for targeted wetland restoration and sustainable urban planning.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.7 Disappeared Waterbodies\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe temporal satellite imagery presented for different Wards of KMC demonstrates notable land cover changes in wetland areas over the past decade. These images, captured at various time intervals, provide evidence of dynamic transformations primarily driven by urban expansion and anthropogenic interventions.\u003c/p\u003e\n\u003cp\u003eIn Ward 117, the wetland area visible in 2011 is gradually encroached upon by built-up structures by 2018, with a further reduction in waterbody clarity observed in 2022. This indicates progressive land-use change and possible illegal infill for development purposes. Similarly, in Ward 119, between 2015 and 2022, substantial urbanization is evident, where once open or vegetated wetland patches have been converted into dense built environments, likely affecting the ecological functioning and groundwater recharge capacity. Contrastingly, Ward 115 reflects some degree of stabilization or partial restoration. From 2015 to 2021, although development surrounds the waterbody, the central wetland area remains mostly intact, possibly due to planning regulations or local conservation initiatives. In Ward 122, the wetland witnessed in 2011 appears increasingly fragmented and encroached by 2022, signifying intensified land-use pressure in a highly urbanized zone (Fig.13.).\u003c/p\u003e\n\u003cp\u003eThese temporal visual analyses underscore the urgent need for stronger wetland protection policies, regular monitoring using high-resolution remote sensing data and community engagement. Without strategic planning and enforcement, such transformations may lead to irreversible loss of urban wetland ecosystems, thereby compromising urban climate resilience, biodiversity, and public health in megacities like Kolkata.\u003c/p\u003e\n\u003cp\u003eThe findings underscore the urgent need for integrated, science-based urban wetland management. A combination of policy reforms, improved land-use planning and public engagement is essential to halt degradation and restore ecological functionality.\u003c/p\u003e"},{"header":"4.\tDiscussion","content":"\u003cp\u003eUrban wetlands play a crucial role in maintaining ecological balance, supporting biodiversity, and offering ecosystem services such as flood regulation and water purification. However, rapid urbanization and unplanned development have led to the degradation, encroachment, and transformation of these fragile ecosystems.\u003c/p\u003e\n\u003cp\u003eThe following case studies underline the scale of urban wetland transformation worldwide, often driven by land-use change, infrastructure development and poor governance. However, innovative urban planning, community engagement and green infrastructure solutions demonstrate potential for restoring and integrating wetlands into cityscapes (Table.1.).\u003c/p\u003e\n\u003cp\u003eTable. 1. Global Scale of Urban Wetland Transformation\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"946\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eInvestigated Regions\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eThreats to Wetlands\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eProposed Interventions\u003c/strong\u003e/\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eRestoration Approaches\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eReferences\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eRio de Janeiro, Brazil\u003cbr\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eWetland loss in low-income peri-urban areas increased vulnerability to flooding and disease\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eIntegrating wetlands into favelas through participatory design and water-sensitive urban design\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003eHerrera (2024)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eBangkok, Thailand\u003cbr\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eWetland transformations under rising urban water demand and land conversion\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eCommunity-based restoration initiatives in restoring hydrological functions and improving resilience\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003ePalakhamarn and Kamolvej (2024)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eBogot\u0026aacute;, Colombia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eLost over 80% of its original wetland coverage due to housing development\u003c/li\u003e\n \u003c/ul\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eCity-led restoration efforts (jaboque and la conejera wetlands) showed ecological improvement\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003ePradilla and Hack (2024)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eLondon, UK\u003cbr\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eAnalyzed shift from neglected wetlands to multifunctional green spaces\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eLea valley wetland restoration project\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003eMell (2022)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eAddis Ababa, Ethiopia\u003cbr\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eDegradation of wetlands due to solid waste dumping and settlement encroachments\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eCommunity-based rehabilitation projects showed success in reviving native vegetation and improving water flow regulation\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003eSoboka and Gemechu (2021)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eShanghai, China\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eInvestigated the transformation of wetlands\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eTransformation of wetlands under the \u0026ldquo;sponge city\u0026rdquo; initiative\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eConstructed wetlands were used to mitigate urban runoff and restore lost functions in urban ecosystems\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003eWu et al. (2019)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eManila, Philippines\u003cbr\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eUrban expansion, industrial discharge, and reclamation projects caused dramatic wetland loss\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eLas pi\u0026ntilde;as-para\u0026ntilde;aque critical habitat established to protect migratory bird habitats and restore hydrological balance\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003eMercado (2018)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eMumbai, India\u003cbr\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eTransformation of mangrove wetlands due to urban expansion and illegal encroachments\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eNeglect of wetland ecosystems worsened flood risks and disrupted coastal biodiversity\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eAdvocating for mangrove restoration.\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003eGupta et al. \u0026nbsp;(2017)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eToronto, Canada\u003cbr\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eWetland degradation due to rapid suburban expansion\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eNew policy instruments, such as wetland offsetting and urban green space zoning\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003eSizo et al. \u0026nbsp;(2015)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eJakarta, Indonesia\u003cbr\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eWetland loss due to land reclamation and population pressures\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eDecreased wetland area exacerbated flooding and deteriorated water quality\u003c/li\u003e\n \u003c/ul\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eUrging for sustainable urban planning and wetland buffer zones\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003eFirman et al. \u0026nbsp;(2011)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eCape Town, South Africa\u003cbr\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eTransformation of seasonal wetlands and fynbos-dominated ecosystems due to urban expansion\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eNeed for biodiversity corridors and ecological infrastructure planning\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003eRebelo et al. \u0026nbsp;(2011)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eSeoul, South Korea\u003cbr\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eInvestigated the Cheonggyecheon Stream restoration, which replaced a buried watercourse with a constructed wetland corridor\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eRevived ecosystem services, improved urban cooling and enhanced public awareness of urban ecology, serving as a global model\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003eCho (2010)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eNew Orleans, USA\u003cbr\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eWetland degradation exacerbated by levee systems and development\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eIncreased vulnerability to storm surges\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eEmphasizing the urgency of wetland restoration\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003eDay et al. \u0026nbsp;(2007)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16.6843%;\"\u003e\n \u003cp\u003eNew York, USA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.2999%;\"\u003e\n \u003cul\u003e\n \u003cli\u003eWetland conversion driven by real estate expansion and infrastructure development\u003c/li\u003e\n \u003cli\u003eFragmentation and biodiversity loss\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.9335%;\"\u003e\n \u003cul\u003e\n \u003cli\u003ePolicies like the clean water act helped reverse some degradation\u003c/li\u003e\n \u003c/ul\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.0824%;\"\u003e\n \u003cp\u003eBolund and Hunhammar (1999)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eSource: Data compiled by the authors\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe transformation of wetlands in the KMC is emblematic of the challenges faced by urban wetlands worldwide. Factors such as land-use changes, pollution and policy gaps have contributed to the degradation of these vital ecosystems. Understanding the dynamics of wetland transformation in KMC is crucial for developing effective conservation strategies and ensuring the sustainability of urban ecosystems.\u003c/p\u003e\n\u003cp\u003eThe following discussion draws upon photographic evidence collected through field surveys across selected Wards (115 to 122) of the KMC. By visually documenting and categorizing various wetland conditions and site statuses, the analysis provides critical insights into the environmental health, anthropogenic pressures, and transitional dynamics of these urban waterbodies. These observations offer a grounded understanding of the spatial and ecological diversity of wetland systems, supporting more effective planning and conservation strategies.\u003c/p\u003e\n\u003cp\u003ePhotographic evidence of clean water conditions (e.g., in Wards 119 and 117) reflects relatively undisturbed waterbodies with low turbidity and high light penetration, often indicative of minimal nutrient load and active hydrological functioning. Conversely, growth of macrophytes in some Wards (e.g., in Wards 115 and 118) is a clear sign of nutrient enrichment, likely due to domestic runoff or untreated greywater discharge. Macrophyte proliferation, while providing temporary oxygenation and habitat, eventually leads to biomass decay, further fuelling eutrophication.\u003c/p\u003e\n\u003cp\u003eMarshland conditions, visible in Wards 115 and 116, show dense, emergent vegetation, indicating stagnant water with low depth and organic-rich sedimentation, an advanced phase of natural wetland succession. Meanwhile, the presence of eutrophication (noted in Ward 117), with green algal blooms and surface scum, points toWard excessive nitrogen and phosphorus input, often linked to fertilizer leaching and sewage influx. water pollution conditions (Wards 115 and 120) display litter accumulation and solid waste deposition, revealing direct anthropogenic interference and ineffective waste management systems. The non-natural waterbody classification (e.g., in Ward 122) depicts encroached or artificially modified water systems embedded within dense urban structures, often functioning more as drainage units than ecological wetlands. unclassified sites, such as in Wards 117 and 120, suggest ambiguous or transitioning landscapes possibly undergoing rapid alteration (Fig.14.).\u003c/p\u003e\n\u003cp\u003eSite statuses such as environmental revival in Wards 118 and 122 illustrates notable community or municipal restoration efforts, visible through cleaner water and active vegetation regeneration. In contrast, swampy areas in Wards 119 and 122 are marked by semi-aquatic, poorly drained regions potentially transitioning into marshland. Disappeared waterbodies (Wards 115 and 118) are especially concerning, revealing either complete infilling, infrastructure development, or seasonal desiccation, a direct outcome of urban expansion or altered catchment hydrology.\u003c/p\u003e\n\u003cp\u003eSites classified as newly identified (Wards 115 and 122) are particularly significant as they suggest previously unmapped or overlooked waterbodies, now discernible due to field validation or seasonal variation. Restricted access in Wards 117 and 120 poses methodological limitations, emphasizing the importance of community engagement and administrative support in comprehensive mapping. Finally, unspecified statuses, such as in Wards 116 and 118, highlight data gaps, either due to field ambiguity or temporal variability, warranting continuous monitoring (Fig.15.).\u003c/p\u003e\n\u003cp\u003eThis photographic dataset reinforces the necessity of integrated field and geospatial assessments in urban wetland studies. It also underscores the spatial variability and pressing threats these ecosystems face within metropolitan contexts, urging for proactive governance and community-led conservation measures.\u003c/p\u003e\n\u003cp\u003eDespite progress, challenges such as land-use conflicts, funding limitations and governance issues persist. Future research should focus on developing integrated management strategies that balance urban development with wetland conservation, considering socio-economic and ecological factors. Efforts must include routine monitoring, expansion of green infrastructure, protection of hydrological connectivity and incentivization of community-based conservation models. Constructed wetlands can serve as a complementary solution especially in areas where natural restoration is unfeasible due to irreversible land-use changes. As part of an integrated wetland management strategy, they present a scalable, community-inclusive approach to rehabilitate ecosystem functions and support sustainable urban development.\u003c/p\u003e"},{"header":"5.\tConclusion","content":"\u003cp\u003eThe integrated field-based and spatial assessment of wetland ecosystems across Wards 115 to 122 in KMC reveals a dynamic and multifaceted landscape shaped by both natural processes and anthropogenic pressures. The temporal analysis of wetland area from 2004 to 2022 across selected Wards of KMC, reveals contrasting trends in spatial transformation. Significant area expansion is observed in Ward 115 and Ward 122, potentially indicating improved mapping accuracy, seasonal variation, or restoration interventions. Conversely, Wards 116 and 117 exhibit a sharp decline, especially Ward 116, which saw over 50% reduction, suggesting encroachment or land-use conversion.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe LULC assessments reveal a sharp decline in ecologically sensitive areas within Borough-XIII over the past decade. Waterbodies, which covered approximately 275.99 ha in 2014, have been reduced drastically to only 55.10 ha in 2024, reflecting a loss of nearly 80% of their original extent. Similarly, vegetation cover has also diminished, while built-up areas expanded from 514.87 ha to 649.56 ha, marking an increase of over 26%. This spatial transformation indicates that urban growth has primarily occurred at the expense of wetlands and vegetative buffers. The MNDWI analysis further highlights fragmentation and encroachment of surface water bodies, particularly in the northern and western wards, where open water features have almost disappeared. Such changes have disrupted the hydrological regime, reduced groundwater recharge potential, and heightened urban flood risks. Moreover, the decline in green and blue spaces exacerbates biodiversity loss, weakens ecosystem service provision, and contributes to the intensification of the warming effects. The method was extremely effective for hydrological study in urban areas since the MNDWI can effectively remove the urban spectral noise, yielding valuable information for the exploration of flood hazard, wetland conservation, and sustainable water resource management in the rapidly developing context of Kolkata.\u003c/p\u003e\n\u003cp\u003eThe photographic documentation, in conjunction with temporal land cover data, provides a robust foundation for understanding the evolving conditions and transformation trajectories of these urban wetlands. While certain Wards demonstrate signs of environmental revival and increased waterbody area, potentially due to better monitoring or restoration initiatives others suffer from rapid shrinkage, disappearance, or encroachment, indicating critical threats to wetland sustainability.\u003c/p\u003e\n\u003cp\u003eThe field condition assessment reveals heterogeneous wetland characteristics. The widespread growth of macrophytes, particularly in Wards 115 and 122 (both above 40%), reflects nutrient enrichment and potential eutrophic conditions. Pollution levels are relatively low overall, peaking at 12% in Ward 119. The site status data across the Wards highlight varied stages of wetland transformation and management challenges. The highest proportion of environmentally revived sites is in Ward 119 (20%), indicating successful ecological interventions. Swampy areas are most prevalent in Ward 122 (29.87%), suggesting retained natural wetland characteristics. Alarmingly, a significant percentage of waterbodies have disappeared, especially in Wards 119 and 120 (36% and 30.77%, respectively), pointing to rapid urban encroachment and land use change.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eRecognizing wetlands as multifunctional assets in terms of biodiversity, climate regulation and social well-being is crucial for shaping resilient, sustainable urban futures. Collaborative efforts between governments, agencies, and communities are vital in addressing flood resilience and ensuring the sustainability of urban wetlands. Ultimately, preserving Kolkata\u0026rsquo;s wetlands is not only an environmental imperative but also a foundational step toward achieving equitable and climate-adaptive urban development.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eDisclosure of Potential Conflicts of Interest\u003c/h2\u003e\n\u003cp\u003eThe authors declare that they have no potential conflicts of interest.\u003c/p\u003e\n\u003ch2\u003eInformed Consent\u003c/h2\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eThe authors declare that no funds, grants, or other forms of support were received during the preparation of this manuscript. Financial support was provided solely during the execution phase of the project and not during the manuscript drafting stage.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eAuthor P.K.R. contributed to the study conception. The methodology and design of the study were contributed by Shilpa Saha. Data collection was performed by S.S., A.B., and A.N. Material preparation, formal analysis and investigation were performed by S.S. and A.B. The first draft of the main manuscript was written by S.S. P.K.R. reviewed the manuscript. Other contributions given by A.D., A.G., and P.R. All authors approved the final manuscript.\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003eThe authors gratefully acknowledge the Kolkata Municipal Corporation (KMC) for providing financial support for the project titled \u0026ldquo;Preparation of an Inventory of Waterbodies by Executing Ground Verification of NRSA (Aerial) Map and Its Correlation with the KMC Tank List\u0026rdquo;, covering Wards 101 to 144 of the KMC. This paper forms a part of the broader scope of this project. The authors also extend their sincere thanks to the Environment and Heritage Department, KMC, for their valuable assistance in facilitating the smooth execution of the research. Gratitude is further expressed to the residents of Borough-XIII of KMC for offering the necessary information and support critical to the successful completion of this study.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAkinbile, C. O., and Yusoff, M. S. (2011). Environmental impact of leachate pollution on groundwater supplies in Akure, Nigeria. \u003cem\u003eInternational Journal of Environmental Science and Development\u003c/em\u003e, \u003cem\u003e2\u003c/em\u003e(1), 81.\u003c/li\u003e\n \u003cli\u003eBolund, P., and Hunhammar, S. (1999). Ecosystem services in urban areas. \u003cem\u003eEcological economics\u003c/em\u003e, \u003cem\u003e29\u003c/em\u003e(2), 293-301.\u003c/li\u003e\n \u003cli\u003eBowen, J. (2000). 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Key technology of ecological restoration demonstration in the Yangtze River Economic Zone and its application. \u003cem\u003eGeology in China\u003c/em\u003e, \u003cem\u003e48\u003c/em\u003e(5), 1305-1333.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Urban Wetlands, Wetland Transformation, Ground Truthing, Ecological Degradation, Sustainable Urban Planning, Eutrophication","lastPublishedDoi":"10.21203/rs.3.rs-7495461/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7495461/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eUrban wetlands play a pivotal role in maintaining ecological balance, regulating hydrology, supporting biodiversity, and offering socio-economic benefits. This study presents a comprehensive, multi-tiered framework for assessing wetland distribution, condition, and transformation in Borough-XIII of the Kolkata Municipal Corporation, India. Employing an integrative methodology that combines high-resolution satellite imagery, GIS-based spatial analysis and systematic ground-truthing, the research identifies both historical trends and current site-specific conditions of wetlands across different Wards. The spatial-temporal analysis (2004\u0026ndash;2022) reveals contrasting trajectories marked expansion in Wards 115 and 122, and significant shrinkage in Wards 116, 117 and 119 attributable to factors such as urban encroachment and partial restoration. The decadal LULC analysis revealed an 80% decline in waterbodies alongside a 26% increase in built-up areas, highlighting rapid urban encroachment. MNDWI results further confirmed fragmentation and shrinkage of surface water features, underscoring urgent conservation needs. Field condition assessments highlight spatial heterogeneity in water quality, eutrophication, and vegetation cover, with macrophyte dominance signalling nutrient loading and altered ecological states. Site status data point to alarming wetland loss in Wards 119 and 120, while emerging waterbodies in Ward 115 suggest improved detection and potential restoration. Temporal satellite comparisons further confirm ongoing degradation, with wetland disappearance driven primarily by infrastructure development. Scientifically, these findings underscore the fragmented and vulnerable state of urban wetlands and highlight the need for integrated watershed management, policy enforcement and community participation. This study introduces the critical role of spatial monitoring and ground validation in guiding sustainable urban planning and ecological resilience in megacities.\u003c/p\u003e","manuscriptTitle":"Spatial-Temporal Assessment of Urban Wetlands in Metropolitan Area, India: A Framework for Sustainable Restoration and Management","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-10 15:09:53","doi":"10.21203/rs.3.rs-7495461/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"497068e8-fcfb-44ed-9d81-35fb16fbd4d0","owner":[],"postedDate":"September 10th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-24T20:38:20+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-10 15:09:53","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7495461","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7495461","identity":"rs-7495461","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}