INTRODUCTION
Mangroves are developing in Bang La, HaiPhong city
Mangroves are essential to the Earth's ecosystem, offering vital services such as protection against natural disasters like tsunamis and tropical cyclones, as well as resources for timber, fisheries, and fodder (Uddin et al., 2013; MFF, 2015; Zulfa and Norizah, 2018) They play a crucial role in sustaining both regional and global ecological balance However, mangrove ecosystems are highly vulnerable to pollution from mining activities, oil spills, heavy metals from shipbreaking, and other industrial processes, as well as disruptions caused by dam and embankment construction (Rahman, 1994; Hossain and Islam).
Mangrove ecosystems exhibit significant biogeochemical vulnerabilities that impact both aquatic and terrestrial flora and fauna This sensitivity can lead to adverse effects on the biodiversity within these environments.
Rising carbon dioxide (CO2) levels in the atmosphere are a significant driver of climate change, leading to increased air and sea temperatures, as well as ocean acidification, which threatens marine ecosystems like coral reefs and mangroves Effective strategies to mitigate greenhouse gas emissions include planting and replanting mangroves, alongside enhancing the protection of existing mangrove forests.
A study by Nguyen et al (2013) highlights the critical role of mangroves in coastal ecosystems, emphasizing their importance in protecting shorelines from erosion and combating climate change.
Over the past 50 years, the destruction of mangroves has accelerated significantly, with ongoing declines reported by experts (Donato et al., 2011; Ambsdorf et al., 2017; Estoque et al., 2018; Radabaugh et al., 2018) This rapid loss is largely attributed to human activities, as mangroves are often perceived as unproductive land Consequently, they are frequently cleared for agricultural practices, human settlements, tourism development, and for resources such as firewood, construction materials, wood chips, pulp, and charcoal.
Mangroves play a vital role in coastal regions by supporting stable food supplies and fostering supplementary economic activities Their unique ecosystems provide significant opportunities for aquaculture, capture fisheries, and port economies, which thrive on the abundant material resources and geographic advantages these areas offer (Thomas et al., 2017; Refinda, 2017; Souza et al., 2018).
Mangroves play a crucial role in supporting aquatic life by providing essential feeding, nursing, and breeding habitats for various species Additionally, these ecosystems are vital for numerous marine mammals and seabirds, highlighting their importance in biodiversity conservation.
2018) An approximate calculation of the mangroves forests area in Vietnam was about 400,000 ha in the beginning of the 20th century (Pham and Yoshino,
2015) Mangroves forests in Vietnam has been using for various purposes (Tien et al., 2018)
A study by Hien et al (2018) highlights that the expansion of aquaculture and other developmental activities in HaiPhong poses a significant threat to mangrove biodiversity and disrupts various economic functions associated with land use Recently, there has been a notable surge in shrimp farming, driven by its potential to boost socio-economic development (Amano et al.).
Effective resource management is essential for meeting human needs sustainably, particularly in the context of shrimp farming, which poses a threat to mangrove ecology To address this issue, it is crucial to update estimates of shrimp farming areas and monitor changes over time Remotely sensed data has been widely utilized for over two decades to map and monitor mangrove environments, providing valuable insights for research and access to mangrove ecology Furthermore, the integration of Geographic Information Systems (GIS) and remote sensing (RS) has enhanced the understanding of vegetation and environmental elements.
Over the past two decades, the coastal zone of Hai Phong has undergone significant changes due to economic and social development, leading to a dramatic decline in mangrove areas and an increase in unproductive land (Evans, 2011; Quang, 2011) Given the vital role of mangroves in environmental health, it is essential to conduct a thorough analysis of land use and land cover changes (LULCC) driven by factors such as tropical storms, inadequate planning, and aquaculture practices Addressing these issues is urgent, alongside the need to develop strategies for the protection and restoration of mangrove ecosystems Therefore, spatial analysis is crucial for assessing long-term LULCC trends, as highlighted by various national and international studies that emphasize the necessity of such analytical approaches in coastal regions.
This project aims to provide recommendations and solutions by utilizing current remotely sensed data sources to evaluate and monitor climatic and non-climatic factors affecting mangrove ecology The focus of the study is to analyze land use and land cover change (LULCC) through spatio-temporal remotely sensed data to address key questions: What is the current status of mangrove management in Hai Phong, Vietnam? How has mangrove vegetation changed over selected years? What future research directions are recommended for improved management?
LITERATYRE REVIEW
Overall GIS and Remote sensing
A Geographic Information System (GIS) is a powerful tool for capturing, storing, analyzing, and presenting various types of geographical data It functions like a web or mobile application, enabling users to integrate their data with maps for effective visualization and analysis This integration helps in identifying patterns and deriving trends from the data.
(Geospatial World, 2018) Fig 2.1 GIS Data Layers, Source:Arizona.edu
A geographic information system (GIS) is a powerful tool that allows users to access a wide range of geographic information and create detailed maps By integrating various data layers, including street, building, and vegetation information, GIS enables comprehensive spatial analysis and visualization.
Fig 2.2 Various use of GIS, Source:Cbronline.com
Geographic Information Systems (GIS) excel in storing and processing extensive spatial data, integrating information from diverse sources regarding content, format, projection, and scale This capability allows for the creation of a unified database that facilitates easy access and analysis Understanding GIS underscores its significance in determining the importance of location and spatial relationships (Nguyen, 2017).
GIS is a powerful tool for analyzing geographic data, revealing enduring patterns and providing valuable insights for problem-solving It allows for the manipulation and synthesis of spatial information, enhancing practical knowledge in specific cases Additionally, GIS facilitates the observation of technical facts related to various programs and serves as a standard reference for historical events.
Landsat imagery is an archive OC earth images Landsat-1 began its journey in
1972 Around the world, Landsat receiving stations are a unique resource for global change researches and used in various fields like Agriculture, Cartography, Geology, Forestry, Regional planning, Surveillance & education
Table 2.1 Types of series of Landsat imagery
Moderate resolution Earth-observing satellites like Landsat play a vital role in monitoring land use and changes over extensive areas Landsat's repetitive and comprehensive observations are invaluable for researchers and managers, enabling them to analyze large geographical regions effectively.
Satellite imagery has become a reliable tool for the consistent monitoring and modeling of land use and land cover patterns (Lo and Choi, 2004; Thakur et al., 2017) Since 2008, Landsat data has been freely accessible, enhancing research and analysis in this field (Salim et al., 2018).
Sentinel-2, an Earth observation mission by the European Space Agency, utilizes a cloud-based platform for efficient distribution management and importing imagery for GIS applications, adhering to OGC standard web services.
Multispectral Imager‟s (MSI), Sentinel-2 launched in 2015 The imagery of Sentinel-2 has three distinguished spatial resolution, they are 10 m, 20 m and
60 m (ESA, 2015) Which can define a very small water area or garden (Hedley et al., 2018) Sentinel-2 data have 13 spectral bands and radiometric resolution of the sensor is 12-bit (ESA, 2015; Tominget al., 2016)
The global application of Sentinel-2 multi-spectral imagery offers valuable multi-temporal coverage, enabling diverse uses in various fields This technology has been instrumental in assessing above-ground biomass in mangroves, monitoring changes in non-forest land use, and evaluating water quality in lakes.
A map is a visual representation that conveys geographic information and real-world features It blends art and science, providing spatial data that enhances understanding An effective map should possess key characteristics such as spatial reference, scale, and a summary of specific information, making it easy to interpret For instance, a village map illustrates these elements clearly.
Application of GIS and remote sensing to detect land use and land cover change
Land use and land cover change (LULC) is a significant process influenced by both natural phenomena and human activities, leading to alterations that affect the natural ecosystem (Ruiz-Luna and Berlanga-Robles, 2003) These environmental changes are particularly concerning today due to human impact Understanding LULC is crucial for effective planning and management of natural resources (Kumar et al., 2013) The transformation of the Earth's terrestrial surface through human actions underscores the importance of LULC in global ecological planning and decision-making for a sustainable future.
Understanding the status of mangroves relies on distinguishing between plant, land, and water objects in remotely sensed data through their reflectivity The use of GIS and remote sensing technology to analyze changes in mangrove ecosystems has gained global popularity (Thi et al., 2014; Thomas et al., 2014).
For decades, GIS and remote sensing techniques have been essential in monitoring urban growth through land use and land cover change detection These technologies play a crucial role in designing and implementing policies aimed at addressing economic, environmental, and social objectives, ultimately contributing to sustainable rural development.
Application of GIS and remote sensing to detect mangrove extents
Mangroves, despite their numerous benefits, are among the most threatened ecosystems globally Unregulated development, including mega-tourism projects, polluting industries, and large-scale shrimp farming, poses significant risks to these vital habitats The use of GIS and Remote Sensing technologies has emerged as a key method for accurately detecting and monitoring the extent of mangrove ecosystems.
Vietnam's mangrove ecosystems are facing significant degradation, necessitating community-led development initiatives that promote economic growth while safeguarding these vital coastal environments Although previous studies on this issue have been limited, recent years have seen a surge of interest from researchers dedicated to the protection of mangroves.
Recent studies over the past five years have revealed significant findings in GIS and Remote Sensing, particularly concerning mangroves and land use/land cover change (LULCC) It is essential to enhance the application of these technologies in this field.
Mangroves
Mangrove is a type forest found in coastal swamps with fines and salty sediments that flooded by tides and abounded by salt-tolerant trees or shrubs(Sheng and Zou, 2017)
Mangroves thrive in tropical and subtropical regions along coastlines and estuaries where freshwater and seawater converge (Bochove et al., 2014) Six distinct types of mangroves exist, classified according to various geophysical, geomorphological, and biological factors (Thom et al., 1984).
- Composite river and wave-dominated
The wave height of the mangrove forests decreases according to the exponential law and the depreciation level depends mainly on three indicators: forest structure, density and forest cover
Mangrove ecosystems cover approximately 137,760 km² across 118 countries, primarily located in tropical and subtropical regions (Alatorre et al., 2016) These vital habitats represent 0.7% of the world's total tropical forest area (Giri et al., 2011) and are predominantly found between latitudes 30° N and 30° S, within the inter-tropical zone that corresponds to the 20°C seawater temperature isotherm Notably, Asia is home to the largest share of mangrove coverage, accounting for 42%, followed by Africa.
Fig 2.4 Spatial distribution of mangroves in the world,
Over the past 50 years, Asia has seen the destruction of 50% of its mangrove areas, with some regions experiencing an accelerating loss Globally, 30% of mangrove forests have vanished (Godoy and Lacerda, 2015), as reported by the FAO.
1994, total coverage of mangrove area is about 5.8 million of hectares, therein 35% of the Mangroves are found in the Caribbean and Latin America (Lugo,
2002), which distributed in 32o 20‟ N latitude at Bermuda, and 28o 30‟ S latitude at Santa Clara, Santa Catarina, Brazil
Africa boasts a total mangrove area of approximately 25,960 km², extending from Mauritania in the northwest (19º 10' N) to Angola in the southwest (10º S), and reaching down to South Africa (29º S).
Mangrove areas in Africa have significantly declined, with studies indicating a loss of 31.5 hectares across 17 estuaries The most substantial reduction has been reported in Nigeria, highlighting the urgent need for conservation efforts in these vital ecosystems (Fatoyinbo and Simard, 2013; Hoppe-Speer et al., 2014).
The mangrove forests of Oceania thrive in a tropical climate characterized by high rainfall and an average temperature of 24ºC This region spans a latitude of 30° and a longitude of 73°, covering approximately 17,590 sq km (Donato et al., 2011) In the Pacific islands, the total mangrove area amounts to around 343,735 hectares, with Indonesia accounting for 23% of the global mangrove cover Australia follows with 977,975 hectares (7.1%), while Papua New Guinea has 480,120 hectares (3.5%) (Chaudhuri et al., 2015) Specifically, Australia boasts nearly 12,000 km² of mangroves, Papua New Guinea exceeds 4,000 km², and smaller areas include 200 km² in Fiji and 640 km² in the Solomon Islands (Ellison, 2000).
The Asian continent boasts the largest and most diverse mangrove area in the world, covering significant regions along the Arabian Sea, Bay of Bengal, and Gulf of Thailand Key contributors to this ecosystem include Indonesia with 3,112,989 hectares (22.6%), followed by Burma (494,584 hectares, 3.6%), Bangladesh (436,570 hectares, 3.1%), Malaysia (505,386 hectares, 3.7%), India (368,276 hectares, 2.7%), the Philippines (263,137 hectares, 1.9%), and Iranian mangrove forests covering 93.37 km² Southeast Asia alone accounts for 33.8% of the world's mangrove forests, highlighting its ecological significance.
Mangroves in Southeast Asia
Southeast Asia is home to some of the most diverse and unique mangrove forests, which constitute 38% of the world's total mangrove area, covering approximately 18 million hectares These rich ecosystems play a crucial role in supporting biodiversity and providing essential environmental benefits.
The tropical zone located between 5° N and 5° S latitude experiences high precipitation and is prone to various natural disasters Recent events, including storms, tsunamis, and cyclones, have been exacerbated by factors such as landslides and deforestation in this region.
Mangrove forests in Southeast Asia are facing significant threats due to the demands of coastal communities living nearby These communities rely on mangroves for fuelwood, leading to over-harvesting and a reduction in silt deposition, which in turn affects freshwater availability and other vital natural resources.
Fig 2.5 Spatial distribution of mangroves in Southeast Asia
In recent years, the rapid expansion of aquaculture, particularly shrimp farming in Southeast Asia, has led to significant environmental concerns Experts indicate that the aquaculture industry is a major contributor to mangrove deforestation, with agricultural practices and the overuse of salt beds exacerbating the issue Over the past 30 years, mangrove areas in Southeast Asia have experienced drastic losses, with reductions of up to 25% in Malaysia and 50% in Thailand (Primavera, 2005).
Considering the benefit of palm oil plantation, local communities and companies are getting more interested, which caused major deforestation in the mangrove forests in Malaysia (Richards and Friess, 2016)
Rapid urban and industrial development in coastal areas is exerting significant pressure on ecosystems Recent studies indicate that economic activities and mining in Vietnam's mangrove regions have led to a substantial decrease in freshwater inflow, resulting in increased salinity and wastewater contamination This situation has severely impacted the biodiversity of mangrove ecosystems.
Table 2.2 Mangrove area in Southeast Asian countries
Rapid urban and industrial development in coastal areas, particularly in Vietnam, has significantly impacted mangrove ecosystems Recent studies indicate that economic benefits derived from mining in these regions have led to a substantial decrease in freshwater inflow, resulting in increased salinity and wastewater accumulation This environmental degradation has severely affected the biodiversity of mangrove habitats.
The mangroves in Vietnam dived into four main zones among a
2012), where zone-I is distributed from Ngoc Cape to Do Son cape,
Zone-II is distributed from to Do
Son cape to Lach Truong cape,
Zone-III is distributed from Lach
Truong cape to Vung Tau cape and
Zone-IV is distributed from Vung
Tau Cape to Nai Cape- Ha Tien
Fig 2.6 Spatial distribution of mangroves in Vietnam,
Importance of mangroves
Mangrove plays an incredible rule in the ecosystem They provide invaluable ecosystem services with a strong foundation for an immensely productive and biologically complete ecosystem(Bochove et al., 2014; Ecoviva, 2016;Huxham
Mangroves, despite comprising less than one percent of global tropical forests, are considered one of the most valuable ecosystems on Earth They offer numerous ecosystem services that greatly benefit humanity, including productive fishing grounds, carbon storage, enhanced tourism and recreation, and protection against soil erosion and destructive tropical storms.
Healthy and intact mangrove forests offer significant opportunities for sustainable revenue through eco-tourism, sports fishing, and various recreational activities, highlighting their potential as valuable natural resources (Ecovita, 2016; Rahman et al., 2017; Ab-Razak et al., 2018).
Buffer zone between land and see
Mangrove serves as a buffer zone between land and sea (Keller, et al,
The mangrove ecosystem, characterized by its rich taxonomical diversity, plays a crucial role in providing shelter along tropical shores It serves as a natural buffer zone, helping to maintain elevation in the upper inter-tidal zone amidst rising sea levels This unique habitat is essential for various species, including salt-tolerant plants, fish, and both terrestrial and aquatic animals.
Mangrove also tends to the first line of defense for coastal communities against tropical storms, cyclone, hurricanes etc (Tanaka, 2009;
Unlimited capacity for absorbing CO2
Mangrove forests play a crucial role in global climate regulation by utilizing sunlight and carbon dioxide through photosynthesis to synthesize organic matter, which helps reduce evaporation On average, they store approximately 10,000 tonnes of carbon per hectare annually in their biomass and soil Additionally, mangroves are integral to the carbon and nitrogen conversion cycle, significantly contributing to carbon dioxide mitigation and helping to combat the greenhouse effect.
Mangroves are vital ecosystems that provide a wealth of resources essential for coastal livelihoods They supply firewood, timber, food, and medicine, making them a significant source of income for many families in coastal regions Mangrove trees are particularly valued for firewood due to their quality and availability, while their timber is sought after for crafting fine furniture and building boats Additionally, mangroves contribute to local economies through the production of honey, which is harvested annually and holds substantial market value.
Mangroves protect both the saltwater and the freshwater ecosystems
Mangroves play a crucial role in preserving water quality due to their intricate root systems, which effectively filter and trap sediments, heavy materials, and pollutants Their dense roots prevent high concentrations of nitrates and phosphates from entering freshwater zones, thereby protecting the aquatic life of insects and fish.
Sedimentation and Prevention of soil erosion
Mangroves are essential for retaining sediments from upstream, which helps prevent contamination of downstream waterways They stabilize sediments through their growth and the deposition of organic matter, contributing significantly to annual siltation and creating fertile land that supports agricultural and fisheries development This expansion of land use has led local governments to consider encroaching on sea dikes Additionally, mangroves play a crucial role in protecting against soil erosion and mitigating damage from tropical storms.
The role of microbial communities in forest
Microorganisms, including bacteria, fungi, yeasts, and other microbes found in soil and mangroves, are essential for decomposing various organic compounds such as starch, cellulose, and chitin These organisms produce powerful exo-enzymes like cellulase and amylase, enabling the rapid breakdown and mineralization of complex substances, including carboxymethyl cellulose and lignocellulose Their vital role in the metabolic cycle significantly contributes to the health of marine ecosystems.
Case study
Mangrove forests play a crucial role in socio-economic development, providing essential resources for local communities and supporting diverse ecosystems that adapt to various climatic and environmental conditions (Huxham et al., 2017; Schild et al., 2018) They not only fulfill basic needs and offer protection against natural disasters but also drive economic growth through their resources (Huxham et al., 2017; Wilson et al., 2018) While mining activities worldwide have significantly contributed to economic progress, they have also led to severe environmental damage (Conlin and Jolliffe, 2010).
A study titled "Application of Analytical Hierarchy Process (AHP) Technique to Evaluate the Combined Impact of Coal Mining on Land Use and Environment: A Case Study in Ha Long City, Quang Ninh Province, Vietnam," conducted by Vu et al (2017) and published in the International Journal of Environmental Problems, highlights the significant environmental impacts of coal mining The research demonstrates that land use and land cover (LULC) changes in the coal mining area are directly proportional to annual coal production, indicating that all types of land in Ha Long City are adversely affected by mining activities.
A study by Umroh (2016) utilized Landsat imagery and GIS techniques to analyze mangrove distribution on Pongok Island The findings revealed that mangroves are densely populated and actively protected by local communities, who demonstrate a strong awareness of conservation efforts and prohibit mining activities in the surrounding areas.
In the 2008 paper "Climate Change and Coastal Vulnerability Assessment: Scenarios for Integrated Assessment" by Nicholls, published in the Integrated Research System for Sustainability Science, the study highlights the significance of evaluating non-climatic drivers contributing to coastal vulnerability The findings underscore the urgent need for integrated assessments to effectively address these non-climatic factors.
Peter Saenger from the School of Environment, Science, and Engineering explores the connections between the environment, economy, and society in his work titled "Sustainable Management of Mangroves," published in the Southern Cross University library The author addresses the challenges associated with existing mangrove management systems and presents a framework for integrated coastal zone management.
(iii) Developing mangrove management plans;
(Nguyen, McAlpine et al.) Reassessing the value of mangroves;
(vi) Rehabilitation of degraded mangroves
A study by Nguyen et al (2013) titled "The Relationship of Spatial-Temporal Changes in Fringe Mangrove Extent and Adjacent Land-use: A Case Study of Kien Giang Coast, Vietnam" analyzes the spatial-temporal changes in fringe mangroves over 20 years using Landsat TM images The findings indicate a significant correlation between increased deforestation and land-use activities such as shrimp farming, crop production, and urban development This research highlights the key drivers of mangrove changes, providing valuable insights for the Department of Planning and Information Development to enhance preservation planning and management efforts.
A report titled "Observatoire des mangroves dans la zone Indo-Pacifique," published by the University of Nouvelle-Caledonia, highlights significant environmental challenges, legal issues, and economic conditions impacting mangrove ecosystems While mining has garnered global attention for its role in socio-economic development, it indirectly affects mangroves through the release of pollutants and sediments, posing a serious threat to both biodiversity and human health.
Mangroves, unique ecosystems found in tropical and subtropical regions, play a vital role in protecting wildlife and providing essential commercial products and ecosystem services To enhance the quality of products and improve environmental conditions, it is crucial to integrate best practices with mining, tourism, and agricultural activities This study proposes a holistic approach to assess and mitigate harmful activities in mangrove areas, aiming for sustainable development and improved mangrove productivity.
RESEARCH OBJECTIVES AND METHODOLOGY
Research goal and objectives
This study focuses on establishing a scientific basis for the detection and monitoring of coastal mangrove extent changes through the use of remotely-sensed satellite data, aiding in sustainable mangrove management amid climate change in Vietnam.
In order to achieve an overall research goal, there are four specific objectives defined as below:
This study aims to assess the current status of mangrove extents and the effectiveness of mangrove management schemes in Hai Phong city province, Vietnam The objective is to provide insights into the existing conditions of mangroves and their management practices in the region.
This study aims to create thematic maps illustrating the extent of coastal mangroves in Hai Phong city for the years 1990, 2000, 2005, 2010, 2015, 2016, 2017, and 2018 The primary objective is to assess the changes in coastal mangrove coverage over these selected years.
- To quantify the changes in coastal mangrove extent during the selected periods (1990- 1995, 1995- 2000, 2000- 2005, 2005- 2010 and 2010- 2015):
This proposed to answer the questions of which period has changed the most and how much
To identify key drivers of coastal mangrove changes during This proposed to answer the questions of what are the drivers of coastal mangrove changes in Hai Phong city
This article aims to identify effective solutions for sustainable coastal mangrove management, focusing on future research directions that can improve management practices.
Research scope
This study concentrated on the coastal districts of Hai Phong city, specifically targeting the mangrove areas It aimed to encompass the entire Tien Lang district and included the Bang La and Dai Hop communes in the Kien Thuy district, where mangrove ecosystems are present.
In this study, multi-temporal Landsat and Sentinel images were used to cover study areas from 1990- 2018 In addition, mangrove extents are quantified during the period 1990- 2018.
Methodology
Human activities and climate change have significantly altered land cover, raising serious concerns about the impact on our environment It is crucial to address these changes and consider their implications for the future.
Hai Phong is an attractive study destination due to its stunning beauty and significance as a hub for recreation, ecological balance, and socioeconomic resources However, the city is currently facing various environmental pollution challenges that threaten the livelihoods of its residents Therefore, it is crucial to implement immediate actions to address these pressing issues.
I am eager to study GIS and Remote Sensing to enhance my expertise in this field The growing interest in Remote Sensing and GIS applications spans across academic, social, and business sectors, highlighting their significance in today's world.
GIS and Remote Sensing studies are essential tools for enhancing mangrove management This study focuses on analyzing Land Use and Land Cover Change (LULCC) through spatiotemporal remotely sensed data to achieve specific objectives.
- To analyze the status and current mangrove management schemes
- To identify key drivers of coastal mangrove changes during the selected periods
- To find out feasible solutions to enhance coastal mangrove management in a sustainable way
Data collecting, synthesizing and analyzing documents have used in the first steps of scientific research
Diagram 3.1 Flowchart of image classification methods applied in this study
Collected data from the field was analyzed by using MS Word, MS Excel and ArcMap
The study will use historical Landsat Thematic Mapper images and
Sentinel images from 1994, 2001, 2006, 2010, 2015, and 2018, along with data from Landsat 7, Landsat 5, and Sentinel 2A/B, have been utilized to analyze changes in coastal land use and specifically in mangrove extents This analysis demonstrates a significant spatial agreement in mangrove distribution, as highlighted by Rudiastuti et al (2016).
Table 3.1Remotely sensed data used this study
No Image codes Date Spatial
Source:Earthexplorer.usgs.gov, Glovis.usgs.gov
3.3.4 Investigation of the status of spatial mangrove extents and current mangrove management schemes
To assess the current status of coastal mangrove extents, this study reviews secondary data and management activities from central and local governments, utilizing historical maps and remote sensing data for accurate mapping (Table 3.1) The resulting map serves to evaluate the present condition of the mangrove areas.
A semi-structured social survey was conducted to collect information on historical records based on the experiences and practices of the local commune
(Dahdouh-Guebas, 2004) It helped us to determine the structure, to review therevious conditions and investigate the environmental factors that have an effect the study area
A comprehensive field survey was conducted to gather data on various aspects, including socio-economic conditions, environmental factors, natural resources, issues related to natural disasters, and climate change management in the study area.
A social survey was conducted among households near mangrove areas, focusing on residents aged 30 years and older who have lived there for over three decades, along with government officials, community managers, and local individuals The discussions centered on their observations in the study area Utilizing the survey data, a sustainable mangrove management model will be proposed to minimize risks, incorporating public consultation and risk assessment strategies.
3.3.5 Construction of coastal mangrove thematic maps in selected years
Preprocessing tools are essential for facilitating change detection and studying vegetation dynamics, which is why ArcGIS was utilized to minimize errors This preprocessing included rectification, re-projection, and registration, as well as addressing topographic and atmospheric effects like clouds Proper projection of a raster dataset required defining its origin, and the re-project tool was employed to convert datasets from one projection to another, with data collected in the WGS 1984 geographic coordinate system Before re-projecting, the coordinate system of the original data was verified, and subsequently, reflectance values from satellite imagery were calculated using the raster calculator in ArcGIS.
Once preprocessing have done, image Interpretationbeen performed in the
After preprocessing, image interpretation was conducted in ArcGIS, leveraging the human eye's ability to perceive red, blue, and green colors for easier visualization of different images This capability is essential for detecting differences between objects and offers the advantage of combining various data pieces to generate unique spectral reflections By integrating the Red (from mangroves), Green, Blue, and NIR bands, a colorful composite raster layer was created, enhancing the analysis of the imagery.
2010), which open nearly true color of the object that we expect in an image (Miller et al., 2017)
ArcTool box => Data Management tools => Raster => Raster processing
RGB (Mangroves, Water, Aquacultures, Others)
Table 3.2 Useful Bands for mapping
As vegetation absorbs nearly all red light this band is useful for distinguishing between vegetation and soil and in monitoring vegetation health
This has similar qualities to band 1 but not as extreme The bandit matches the wavelength for the green we see when looking at vegetation
Open water, generally with greater than 95% cover of water, including streams, rivers, lakes, and reservoirs
Construction, residential, commercial, industrial, transportation and facilities, grass, sod, timber trees, shrubs, other live ground covers
3.3.5.3 Normalized Difference Vegetation Index (NDVI)
Satellite images were enhanced using vegetation indices, specifically NDVI, to accurately identify the extent of mangroves Land use and land cover (LULC) classification was essential for detecting temporal changes in mangrove areas In this classification, mangrove vegetation is assigned a value of 1, water bodies a value of 2, and other land types—including other plants, residential areas, and bare or wet soils—a value of 3, while agriculture and aquaculture receive a value of 4 Higher NDVI values indicate denser mangrove populations, with values close to -1 representing non-vegetation, such as water or bare soils, and values approaching +1 indicating dense vegetation.
1 𝑁𝐷𝑉𝐼 = 𝑁𝐼𝑅 – 𝑅𝐸𝐷/𝑁𝐼𝑅 + 𝑅𝐸𝐷 (Pervin et al., 2016; Nguyen, 2017) Where: NIR is Near Infrared, RED is (visible) Red
The range of NDVI is from -1 to 1
Table 3.3 NDVI values for various cover types
Rock, sand, or snow NDVI