Integrated, sustainable management of mangrove forest in the context of climate change a case study in xuan thuy national park, nam dinh province

VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY PIYA THAMMAVONGSA INTEGRATED, SUSTAINABLE MANAGEMENT OF MANGROVE FOREST IN THE CONTEXT OF CLIMATE CHANGE: A CASE STUDY IN

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

PIYA THAMMAVONGSA

INTEGRATED, SUSTAINABLE MANAGEMENT OF MANGROVE

FOREST IN THE CONTEXT OF CLIMATE CHANGE:

A CASE STUDY IN XUAN THUY NATIONAL PARK,

NAM DINH PROVINCE

MASTER’S THESIS

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

PIYA THAMMAVONGSA

INTEGRATED, SUSTAINABLE MANAGEMENT OF MANGROVE

FOREST IN THE CONTEXT OF CLIMATE CHANGE:

A CASE STUDY IN XUAN THUY NATIONAL PARK,

NAM DINH PROVINCE

MAJOR: CLIMATE CHANGE AND DEVELOPMENT

CODE: 8900201.02QTD

RESEARCH SUPERVISOR:

Dr HOANG THI THU DUYEN

Dr NGUYEN THI THUY HANG

Hanoi, 2022

PLEDGE

I assure that this thesis is original and has not been published The use of results

of other research and other documents must comply with regulations The citations and references to documents, books, research papers, and websites must be in the list of references of the thesis

Author of the thesis

Piya Thammavongsa

TABLE OF CONTENT

PLEDGE i

TABLE OF CONTENT ii

LIST OF TABLES i

LIST OF FIGURES ii

LIST OF ABBREVIATIONS iii

ACKNOWLEDGMENT iv

INTRODUCTION 1

1.1 Background 1

1.2 Overview of previous researches 2

1.2.1 Mangroves and their functions 2

1.2.2 The concept of integrated, sustainable management of mangrove forest 6

1.2.3 Integrated and sustainable management of mangrove in XTNP 7

1.3 The necessity of the research 7

1.4 Research Framework 8

1.5 Research objectives and scope of the research 8

MATERIALS AND METHODOLOGIES 10

2.1 Materials 10

2.1 Methodologies 10

2.1.1 Impact observation 10

2.1.2 Mangrove structure evaluation 10

2.1.3 Narrative review 11

2.1.4 Household farmer survey 11

2.1.5 Analysis of carbon sequestration in soil 12

2.1.6 Data processing 14

RESULTS AND DISCUSSION 15

3.1 Features of mangrove forest at Xuan Thuy National Park 15

3.2 Contribution of mangrove forest in climate change mitigation and adaptation 16 3.2.1 Contribution of mangrove forest in climate change mitigation 16

3.2.2 Contribution of mangrove forest to climate change adaptation 18

3.3 Current practice on management of mangrove forests in XTNP 22

3.4 Challenges on mangrove forest management in XTNP 26

3.4.1 Climate change and disasters 26

3.4.2 Economic development objectives 30

3.4.3 Other challenges 31

3.5 Recommendations for integrated, sustainable management in XTNP 32

3.5.1 Mitigation and adaptation ability of mangrove to CC 32

3.5.2 Significance of mangrove conservation in the context of climate change 32 3.5.3 Integrating CC mitigation and adaptation countermeasures 33

3.5.4 Recommendations for sustainable development of XTNP 35

CONCLUSIONS AND RECOMMENDATIONS 37

REFERENCES 38

APPENDIX 1: Questionnaire for survey 42

APPENDIX 2: Mangrove measurement 50

i

LIST OF TABLES

Table 3.1 Tree density 15

Table 3.2: Carbon stock in mangrove soil and bare land to the depth of 90 cm 17

Table 3.3 List of extreme events existing in XTNP according to survey results 28

Table 3.5 Ecotourism-related services in XTNP 19

Table 3.5 Options to face with climate change impact 34

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LIST OF FIGURES

Figure 1.1: Ecosystem services of mangroves 3

Figure 1.2: Climate change impacts on mangroves 4

Figure 1.3: Research framework 8

Figure 3.1: Distribution of mangroves in the studied plot (10 m x 10 m) 15

Figure 3.2: Tree height and diameter (Bars represented standard deviation) 16

Figure 3.3: Carbon (OC) content (%) in mangrove soil and bare land 16

Figure 3.4: Carbon content (mg/cm3) in mangrove soil and bare land 17

Figure 3.5: Main livelihood in Giao Thien commune 18

Figure 3.6: Contribution of main livelihood / total income (%) 18

Figure 3.7: Evaluation of importance of mangrove in local livelihood 19

Figure 3.8: Mangrove conservation impacts on income 20

Figure 3.9: Role of mangrove in DRR 21

Figure 3.10: People's awareness about role of mangrove in DRR 21

Figure 3.11: Roles in mangrove forest management in XTNP 22

Figure 3.12: Opinion about mangrove management job 23

Figure 3.13: Option toward mangrove conservation 24

Figure 3.14: Willingness toward mangrove conservation 24

Figure 3.15: Perspective of respondents about the importance of mangroves protection and conservation 24

Figure 3.16: Respondents’ willingness to plant the mangrove 25

Figure 3.17: Mangrove conservation activities that respondents are willing to do 26

Figure 3.18: Average annual temperature at Van Ly station and Nam Dinh station (⁰C) 26

Figure 3.19: Total precipitation at Van Ly station and Nam Dinh station (mm) 27

Figure 3.20: The adjustment of survey respondents about the change of mangrove areas compared to 5 years before 29

Figure 3.21: Income from hand collection per hectare per year 31

iii

LIST OF ABBREVIATIONS

CC: Climate change

IPCC: Intergovernmental Panel on Climate Change

OC: Organic carbon content

XTNP: Xuan Thuy national park

iv

ACKNOWLEDGMENT

To complete this thesis, I would like to thank the lecturers and staff of the Program on Climate Change and Development, Vietnam Japan University, Hanoi National University for their supports My research cannot be successful without their advices and collaboration

First and foremost, I would like to express my gratitude and sincere thanks to Dr Hoang Thi Thu Duyen and Dr Nguyen Thi Thuy Hang, who directly supervised my research implementation, for their enthusiastic instruction and dedication to orient my research topic, data processing, and analysis

I would like to dedicate this thesis to my parents, my wife, my children and my friends as a gesture of thanks for their support and putting their trust in me In the process

of studying, researching and implementing the topic, I have also received a lot of valuable attention, suggestions and support from teachers, colleagues, friends from Vietnam Japan University

1901 and 2018 Climate change also can increase the severity of natural disasters, both

in intensity and frequency With the coastline stretched more than 3,200 kilometers long, Viet Nam is one of the countries in the world that are most affected by climate change (World Bank 2020) In Vietnam, the annual average temperature in 1958-2014 increased

by about 0.62⁰C, the water level at stations tended to increase by about 3.34mm/year (MONRE, 2016) Extreme weather events and climate change also affect significantly the balance of forest ecosystems, agriculture and aquaculture, particularly in the coastal area As most of the coastal population often lives in these geographically vulnerable areas while the capacity for adaptation is limited, the resources to respond to climate change are inadequate Meanwhile, the main income of local people comes from livelihood activities that are vulnerable to the impacts of climate change such as agriculture, fisheries, and forestry

Mangrove ecosystem plays important roles in the economic development and environmental protection Mangrove ecosystem supports a variety of economic activities, such as firewood, charcoal, shrimp and crab farming, etc Mangrove ecosystem stabilizes coastlines, promotes coastal accretion and provides a natural barrier against storms and tidal bores In addition, mangrove forest is a carbon sink accumulating atmospheric CO2, contributing to the reduction of greenhouse gas emissions As the largest coastal wetland ecosystem in the north of Viet Nam, Xuan Thuy National Park (XTNP) was chosen as a typical research site XTNP is located in the southwest of Giao Thuy District, Nam Dinh Province, right at the Red River’s mouth: Ba Lat estuary The entire buffer zone and core area of the park are located in 5 communes including Giao Thien, Giao An, Giao Lac, Giao Xuan, and Giao Hai In

1989, this area was recognized as the 50th Ramsar of the world and the first Ramsar area

of Southeast Asia and Vietnam (Ramsar, 1992) By 2003, XTNP was raised from Xuan

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Thuy Wetland Reserve under Decision No 01/2003/QD-TTg of the Prime Minister of the Socialist Republic of Vietnam, January 2nd, 2003 The total area is about 7,100 hectares, including 3,100 hectares of forested floating land and 4,000 hectares of mangroves (Decision 01/2003 / QD -TTg) In 2004, UNESCO continued to recognize the inter-provincial coastal biosphere reserve in the Red River Delta, of which XTNP became the essential core area (UNESCO, n.d.) However, thoroughly understanding the response of XTNP to climate change and evaluation of the mangrove recovery from climate change impact is still lacking

1.2 Overview of previous researches

1.2.1 Mangroves and their functions

Mangrove is a group of trees that live in coastal saline or brackish water in the tropics and subtropics, including more than 50 mangrove species, with the most diversity in Asia, followed by eastern Africa (FAO, 2007) The term ‘mangrove’ describes both the ecosystem and the plant families that have developed specialized adaptations to live in this tidal environment (Tomlinson, 1986) Plant species of mangrove are divided into two groups: true mangrove species and associated mangrove species (Phan, 1999) Mangrove ecosystems are susceptible to climate change impacts such as sea-level rise; change in temperature; changes in precipitation; changes of the chemical composition of the atmosphere and oceans; increase in the frequency, severity, and duration of extreme weather; and so forth (Jennerjahn et al., 2017) Jennerjahn et al (2017) also indicated that beside anthropogenic impacts, all of these changes are likely

to affect mangrove distribution, diversity, productivity, resistance, resilience, and so on

in both direct and indirect ways Hutchings & Saenger (1987) stated that mangroves are most productive within the temperature range of 15 – 25 ⁰C The increase of temperature and CO2 level could increase mangrove productivity and respiration, change the timing

of flowering and fruiting, expand their range into higher latitudes (Ellison, 2000) Mangroves are likely to have the adaptive capacity with temperature changes, but if the temperature rises to more than 40 ⁰C, the leaves could stop photosynthesizing

Xuan Thuy National Park is a Ramsar site in Southeast Asia where 202 flora species exist, in which there are 18 true mangrove species, including some main species:

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Aegiceras corniculatum, Sonneratia caseolaris, Kandelia 3 bovate, and Rhizophora stylosa, and 88 associated mangrove species Besides, some mangrove species were imported from other countries, such as Sonneratia apetala, Avicennia marina, and Bruguiera gymnorrhiza (Department of Biodiversity Conservation, 2015; Phan, 2018) Mangroves have been found to provide a great variety of ecosystem services for society, ranging from environmental, cultural, social to economic values (IUCN Vietnam, 2012),

which are divided into four main functions (Error! Reference source not found.)

Figure 1.1: Ecosystem services of mangroves (IUCN, 2012)

These four functions contribute great values for Climate Change Adaptation and Mitigation that will be mentioned further in this study

Mangrove and climate change adaptation

The mangrove ecosystem has great implication to climate change adaptation A study on the impacts of mangrove afforestation in Northern Vietnam (Pham et al., 2019) has shown that with the ability to reduce erosion, mangrove provided protection to the dyke system, private assets Also, mangrove significantly increases the yield of aqua production, providing frequent income for households who relied on fishing in the forest For coastal protection, the mangrove could dissipate the energy of wave and wind, reduce wave height by 13 to 66% over a 100 m of mangrove thickness (McIvor

et al., 2012) However, the effect of the mangrove forest may vary with density and height of the trees (McIvor et al., 2012)

•Reduced erosion

•Stabilization and accretion of land

•Water quality maintenance

•Climate regulation

SUPPORTING

•Primary production (carbon sequestration)

•Nutrient cycling

CULTURAL

•Tourism and recreation

•Spiritual appreciation

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The ecosystem service of XTNP is on the brink of decline over intensive land exploitation for aquaculture in the buffer zone, aquaculture exploitation under the mangrove in the core zone A research by Hung et al (2020) showed an increasing awareness of local community on the roles of mangrove ecosystem in natural hazard prevention, aquatic product provision Local people also recognize the importance of Xuan Thuy National Park in preserving ecosystem services for future use and other human activities

Impacts of climate change on mangroves

In the context of climate change, mangroves are under threats These impacts are

briefly demonstrated in Error! Reference source not found

Figure 1.2: Climate change impacts on mangroves (McKee et al., 2012)

Amongst several factors above, sea level rise and storm are two main drivers that impact mangrove growth Rising volatility in external force due to sea level rise is a major threat to the mangrove ecosystem IPCC (2014) projected the global mean sea level rise from 1990 to 2100 could be up to 0.88 m The rate of sediment intrusion, inundation and salinity may increase The mangrove species have certain physiological threshold of environmental tolerance, which are sensitive to the change in inundation cycles and salinity level (Ball, 1988; Friess et al., 2012) In addition to high tidal wave and storm destruction, the seaward mangrove would decline and may develop landward which then face human pressure – from land use to the fluctuation of fresh water flow and declination of river sedimentation due to hydroelectric development Without

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efforts to conserve and expand the mangrove forest, the “coastal squeeze” from the sea and human pressure could put the mangrove ecosystem on a decline (Alongi, 2008)

Impacts of storms on mangrove forests

The development of mangrove in response to sea level rise also relies on the rate

of sedimentation accretion If the sedimentation rate is slower than the rate of sea level rise, the mangrove seaward would be drawn, though the rising tidal would take the mangrove landward (Alongi, 2014) If the accretion rate exceeds the local sea level rise, the mangrove would expand seaward while the terrestrial plant would develop seaward (Alongi, 2014)

IPCC AR5 (2014) reports projected that the frequency and intensity of typhoon would increase due to global warming Heavy storms do both harm and constructive impacts to the mangrove ecosystem, which may depend on the location of the mangroves and the characteristic of the storms like wind velocity and storm surge which delivers high tides (Krauss et al., 2005; Piou et al., 2006) Typhoons typically ravage the seaward mangroves, defoliate the leaves and break the branches At worst, it can lead to the removal of mangroves Google Earth imagery over Xuan Thuy National Park still shows the mangrove islets with dark colors patches behind its green outer bushes, which resulted from storm events On the bright side, storm can quickly deliver allochthonous sediment to increase the soil elevation (Smith et al., 2009; Smoak et al., 2013) Increase in soil elevation would also mitigate the impacts of sea level rise against the integrity of the mangrove forests However, the resilience of mangrove forest against the storm is also influenced by the species specific and the general position of the mangrove (Aung et al., 2016)

Though the increase in atmospheric CO2 concentration and temperature is likely

to increase mangrove productivity, some certain mangrove species would be sensitive

to the increasing heat wave and cold snap events, especially for the climate of the Xuan Thuy National Park The degradation of mangrove ecosystem would threat the ecosystem service in term of protective capacity and food source

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1.2.2 The concept of integrated, sustainable management of mangrove forest

Climate change or resource depletion/scarcity has become big issues in the 21stcentury (UNEP, 2012), and there is interconnectivity between the issues In such a context, there requires solutions and actions on use and management of resources for sustainable development Integrated management and sustainable management are endorsed for management of natural resources by various enterprises, countries, and international organizations (the United Nations, the European Commission)

The concept of integrated resource management (IRM) or integrated natural resource management (INRM) refers to the way of using natural resources so as to harmonize between use and conservation of the resources (Florin & Gabriel, 1991) Applying IRM means to integrate various resources (both human and natural resources (Boris, 2016), community involvement, technical knowledge , and organizational structure and policy objectives (Jennifer A Bellamy, 1999) in the process

Together with integrated management, sustainable management of resources are also promoted widely Aiming at achieving the Sustainable Development Goals (SDG) no

12 - ensure sustainable consumption and production patterns, sustainable management

is described in item 12.2 that “by 2030 achieve sustainable management and efficient

use of natural resources” (THE 17 GOALS | Sustainable Development, n.d.) This shows

the importance and necessity of sustainable management for sustainable development The application of sustainable resource management has also been emphasized by the United Nations Framework Classification for Resources; in which, sustainable resource management implies the manner of managing resources sustainably, requiring the involvement of all stakeholders, including governments, industry, investors and communities (United Nations, 2020), and the needs for integrative, adaptive and interactive approach in the process (Smith, 2014) It is recommended that the principles

of sustainable resource management include: (1) secure the adequate supply and efficient use, (2) maintain life-supporting functions & services, (3) provide for the basic institutions of societies and their co-existence with nature, (4) minimize risks incurred

by dependence on resources, (5) contribute to fair distribution, (6) minimize problems between related sectors, and (7) drive resource productivity (Bringezu & Bleischwitz, 2017)

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In the context of climate change and global change, natural resources are becoming seriously affected and depleted for various causes The application of integrated and sustainable management of resources has been implemented extensively and has brought in positive results

1.2.3 Integrated and sustainable management of mangrove in XTNP

As an important Ramsar site of Vietnam, XTNP has been receiving significant investment and attention from both private and public sectors Following the Decree 66/2019/NĐ-CP on conservation and sustainable use of wetlands and various legal documents, sustainable use and sustainable management of wetlands are specified, aiming at balancing the interests of all stakeholders, and harmonization of use and conservation

According to the regulations on nature conservation and regulations on the wise and sustainable use of wetland resources in the Xuan Thuy Ramsar site, XTNP has established a mechanism aiming at enhancing community participation in use and management in the buffer zone (Bao Nam Dinh, 2019) Numerous models of mangrove management has proved to be efficient, that is beneficial for stakeholders, namely the model of co-management of mangrove forests sponsored by the IUCN (XTNP, 2021)

1.3 The necessity of the research

XTNP is characterized by mangrove ecosystems with high biodiversity, home of many rare species Not only is the mangrove forest rich in biodiversity, but it also provides essential ecological functions and services (Xuan Thuy National Park, n.d.), such as coastal protection and development, nurturing economic value aquatic species, and also providing daily biological resources for the local community

However, XTNP is facing many pressures, leading to the degradation of ecosystems and mangrove forests Some reasons are: destroying mangroves for shrimp farming; illegal and excessive exploitation of biological resources; water pollution; rising of the local population; the effects of climate change, sea-level rise, and saline intrusion gradually deepen inland (Hoang and Helmut, 2015) Therefore, although there have been many studies on mangrove forests, as well as many solutions have been taken

to protect the forest and ensure a sustainable source of livelihood for people in XTNP,

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further works need to be done This research aims at providing more updated information on the current state of the mangroves, as well as to learn more about the perceptions of local authorities and people about forest ecosystem services and mangrove conservation From the results and findings, the research will make conclusions and recommendations to help the government get more information and scientific data to come up with suitable solutions and appropriate policies

1.4 Research Framework

The research integrated primary and secondary data in alignment with climate change situation, economic values of the mangrove ecosystem, and disaster

management in the area (Error! Reference source not found.) Based on the collected

data, mangrove monitoring in response to climate change and its contribution to livelihood of local people was evaluated through carbon sequestration, coastal resilience, aqua product values, disaster awareness and conservation awareness The outcomes would provide background for policy makers to make solution to mitigate and adapt to climate change

Figure 1.3: Research framework

1.5 Research objectives and scope of the research

Research objectives:

General objective

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The major aim of this research is to research on the current practice and propose recommendations on the integrated and sustainable management of mangrove forest in the context of climate change in Xuan Thuy national park, Nam Dinh province as a case study

Specific Objectives:

 Investigate the contribution of mangrove forest in CC mitigation and adaptation;

 Investigate current practice on management of the mangrove forest in XTNP;

 Investigating the challenges on management of mangrove forests in XTNP; + Impact of climate change on management of mangrove forest and the livelihood of the local people;

+ Other challenges on mangrove forest managements

 Propose recommendations for integrated and sustainable management of mangrove forest in the context of CC

The project was implemented to answer following research questions:

 What are characteristics of mangrove forest at XTNP? How does mangrove forest contribute to climate change action?

 What is the impact of climate change on mangrove forest and livelihood?

 What is the situation of mangrove management in XTNP?

 What are integrated and sustainable management solutions of mangrove in the context of climate change?

Scope of the research:

The scope of the research covers the mangrove forest

2.1 Methodologies

2.1.1 Impact observation

A field trip around the mangrove forest was set-up in Ba Lat river mouth to directly observe some natural impacts This observatory section helped the author to understand how vulnerable the mangrove is to natural disaster

2.1.2 Mangrove structure evaluation

To evaluate the mangrove structure and to analyze the role of mangroves in carbon sequestration, a plot of 10 m x 10 m in the 3-year-old planted mangrove area was studied

The number of tree species in the plot were counted At the same time, each tree’s height and diameter were also measured The tree height was estimated from the surface

to the top using a stick marked every 0.5 m Diameter at breast height (DBH) was measured using a tape and divide by pi The diameter of trees which branched below 1.3

m (as for Sonneratia caseolaris) or 0.3 m (as for Kandelia obovata) was measured at the height that the trees started branching

The mean height and diameter of each species and their standard deviation were then calculated using Equations 1 and 2

x̅ = x1+ x2+ ⋯ xN

Where: x: tree height (m) or diameter (cm)

x̅: mean tree height (m) or diameter (cm)

N: number of trees

2.1.3 Narrative review

Narrative review method was applied to collect expert data of the mangrove ecosystem, climate change, and climate variables In order to thoroughly understand the role of mangrove ecosystem in XTNP, and the linkage between mangrove and climate change, professional information was collected from numerous researches, reports, especially information provided by the Board of Management of XTNP, with reference

to other mangrove ecosystems, and biosphere reserves Climate change variables were obtained from available hydrometeorology reports, including records from Van Ly meteorology station Narrative review also provided other necessary information and focused areas of inquiry

2.1.4 Household farmer survey

A socio-economic household survey (Appendix 1) was conducted for 51 households whose livelihood depends on collecting aquatic products from the mangrove forest in Giao An commune The survey was designed to assess the impact of climate change on mangroves as well as to evaluate the vulnerability of mangroves, and since then proposed a solution to adapt to climate change, demonstrated evidence of climate change impacts on mangrove forest functions through socio-economic evaluation The survey consisted of four main parts: (1) General information about respondents, (2) Impacts of climate change, (3) Vulnerability and (4) Hand collectors' awareness about

2.1.5 Analysis of carbon sequestration in soil

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At each plot, we collected one soil core to evaluate the carbon sequestration function of mangroves, and three soil cores in the nearby bare land were sampled to make a control treatment Briefly, there were six cores to be collected

During the process, two probes were used Each core was taken to a depth of 1

m The cores after taken out from the probe were cut into pieces of 10 cm in width (corresponding to its depth), then each sample was stored in a plastic bag written location taken, core number in the location, depth in centimeter (e.g SF1 0 - 10, BL2

10 - 20, etc in which ‘SF’ denoted surface of planted mangrove and ‘BL’ denoted bare land) Therefore, there were total 60 soil samples to be analyzed

2 Cr2O72- + 3 C + 16 H+ → 4 Cr3+ + 3 CO2 + 8 H2O The Cr2O72- reduced during the reaction with soil is proportional to the oxidisable organic C present in the sample The organic carbon was estimated by measuring the remaining unreduced dichromate by back-titrating with ferrous sulphate or ammonium ferrous sulphate using diphenylamine or o-phenanthroline-ferrous complex as an indicator

6 Fe2+ + Cr2O72- + 14 H+ → 2 Cr3+ + 6 Fe3+ + 7 H2O Alternately the organic carbon can be calculated from the amount of chromic ion (Cr3+) formed, using a colorimetric procedure measuring absorbance at 588 nm (after Sims and Haby, 1971) An advantage of this procedure over the titrimetric method is that accurate standardization of the Cr2O72- solution is not required

The calculation is:

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𝑂𝑟𝑔𝑎𝑛𝑖𝑐 𝑚𝑎𝑡𝑡𝑒𝑟 (%𝑂𝑀) = (𝑉𝑏𝑙𝑎𝑛𝑘− 𝑉𝑠𝑎𝑚𝑝𝑙𝑒) × 100 × 1.724 × 𝑚𝑐𝑓 × 0.003 × 𝑀𝐹𝑒2+

𝑊

𝑉𝑏𝑙𝑎𝑛𝑘 = volume of titrant in blank, mL

𝑉𝑠𝑎𝑚𝑝𝑙𝑒 = volume of titrant in sample, mL

𝑀𝐹𝑒2+ = concentration of standardized FeSO4 or (NH4)2 Fe(SO4)2.6H2O solution, molarity

f = correction factor, 1.3

W = weight of moist soil, g

mcf = Moisture correction factor (refer to SOP for Moisture Content to compute for the mcf value)

1.724: conversion factor of concentration of carbon associated with organic compounds (Corg)

0.003: each Cr2O72- molecular weight oxidizes 0.003 g cacbon

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RESULTS AND DISCUSSION

3.1 Features of mangrove forest at Xuan Thuy National Park

The number of trees in the studied plots was about 58, including 2 species:

Sonneratia caseolaris (SC) and Kandelia obovata (KO) The two species were planted

in tandem in the plot (Figure 3.1)

10 m

Averaged tree height and diameter, and tree density were presented in Figure 3.2 and Table 3.1, respectively The raw data was presented in Appendix 2 showed the growth characteristics of the trees distributed in the plots

As for Sonneratia caseolaris, the mean height was 4.56 ± 0.68 m, and the mean diameter was 25.21 ± 9.39 cm As for Kandelia obovata, the mean height was 1.18 ±

1.28 cm, and the mean diameter was 9.35 ± 4.58 cm

Table 3.1 Tree density

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3.2 Contribution of mangrove forest in climate change mitigation and adaptation

3.2.1 Contribution of mangrove forest in climate change mitigation

60 soil samples were collected, in which SF1, BL1 and BL3 had samples from 0

- 10 to 80 - 90, SF2 and SF3 had samples from 0 - 10 to 90 - 100, and BL2 had samples from 0 - 10 to 100 - 110 The percentage of OC content in each layer is demonstrated in Figure 3.3 Carbon (OC) content (%) in mangrove soil and bare land It can be shown that the OC in the upper soil layers are higher than that in the lower soil layers in both types of land Although the difference is not significant, in general the percentage of OC content in the mangrove soil is higher than that in the bare land, especially with the top

10 cm

Figure 3.3 Carbon (OC) content (%) in mangrove soil and bare land

Figure 3.2 Tree height and diameter (Bars represented standard deviation)

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However, in Figure 3.4, it cannot be concluded about the difference between the carbon content (mg/cm3) in mangrove soil and bare land It was calculated that the carbon stock to the depth of 90 cm in the mangrove was 184.01 tC/ha, lower than that

in the bare land which was 242.84 tC/ha This result is different from that in the research

of Ha (2018), in which the carbon content (mg/cm3) in soil of the 18 to 20-year-old

planted Kandelia obovata mangrove area in Xuan Thuy National Park was higher than

that in the bare land Also in Ha’s research, it has been found that the carbon content increased with the age of mangroves Therefore, our different result may be derived from the smaller age of mangroves (3 years old), limitation in experiment process or some unknown knowledge about the area Nonetheless, the decreasing trend with depth

of carbon content in mangrove soil is similar to that in Ha’s research

The result from this research did not include the carbon stock in mangrove roots and above-ground biomass (stems, leaves, branches); therefore, in reality the carbon stock in the mangrove is certainly higher than this result, showing the carbon sequestration potential of mangroves in Xuan Thuy National Park

Table 3.2: Carbon stock in mangrove soil and bare land to the depth of 90 cm

Figure 3.4 Carbon content (mg/cm 3 ) in mangrove soil and bare land

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3.2.2 Contribution of mangrove forest to climate change adaptation

3.2.2.1 Mangrove role in livelihood improvement

The research found out that mangrove ecosystems play a crucial part in the livelihood activities of the local people

Among 51 respondents participated in the interview, up to 41% (equivalent to 21 households) share that their livelihoods are directly related to mangrove ecosystem, these activities include aquaculture/fishing, and bee raising (Figure 3.5)

Figure 3.5: Main livelihood in Giao Thien commune

Figure 3.6: Contribution of main livelihood / total income (%)

Though almost 100% of respondents respond that their families remain agricultural cultivation (rice production) and cattle & poultry breeding (chicken, duck,

Aquaculture raising &

Fishing

Service &

Trading

Wage earner

Bee raising Salary (local

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cow), these activities do not bring in much economic value but to serve the demand of

the family only It appears that mangrove-related activities (mostly aquaculture/fishing

and bee raising) are contributing largely to family’s income, it becomes the main

livelihood source for up to 41% of the interviewed households (Figure 3.6)

Furthermore, respondents’ answer also revealed their evaluation about the

importance of mangrove ecosystems in maintaining livelihood for local people

Figure 3.7 Evaluation of importance of mangrove in local livelihood

Accordingly, 100% respondents recognize the importance of mangrove to the

livelihood of local people, the majority (~92%) believe that mangrove is very important,

and even extremely important to their livelihood (Figure 3.7) Among major aquaculture

activities, raising shrimp and clamp in the buffer zone along mangrove forest are the

most popular models with the most economic benefits so far in Giao Thien commune

Being the first Ramsar site in Vietnam and Southeast Asian with its unique and

rich biodiversity, XTNP becomes an attractive tourist spot in Xuan Thuy district

Tourism creates livelihoods for a number of families (Table 3.3)

Table 3.3 Ecotourism-related services in XTNP (Source: MBNP)

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6 Arts (indigenous culture; “chèo” ) 8

8 Car and vehicle rental service 4

Apparently, mangrove has shown its huge contribution to ensure and improve the livelihood of the local people

One of the focus of the research is to investigate local people’s willingness toward mangrove conservation 75% of respondents reply that conserving mangrove does not exert any impacts on their family income when being asked whether mangrove conservation impacts income of the local people

Figure 3.8: Mangrove conservation impacts on income

Surprisingly, the rest 25% answer that their income would increase thanks to mangrove conservation Mangrove conservation creates favorable conditions for aquaculture activities, bee raising; increases the number of tourists, and protects the community from climate-induced loss and damages

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3.2.2.2 Mangrove role in disaster risk reduction

Many researches prove the importance of mangrove ecosystems in reducing disaster risks in coastal areas, the ecosystem is working as “Green dyke” to protect the coastline and the communities inside the coastline from climate-induced hazards Researches by UNDP (2004) and UNFCCC (2007) have pointed to 70-90% reduction

of wind-generated energy due to mangrove forest In Bangladesh, the roles of mangrove forests were seen in coastal protection form storm surges, waves, tidal currents and typhoons (Barua et al., 2010) In this study, the research team aims to investigate people’s awareness about this function

In general, up to 90% of

respondents reply that mangrove is

important in disaster risk reduction

(DDR)

They also shared that without

mangrove, the community would be

badly affected by natural disasters,

like typhoons

Figure 3.9 Role of mangrove in DRR

Fi gure 3.10: People's awareness about role of mangrove in DRR

To be more specific, survey results show that the majority of respondents 90%) are well aware of mangrove’s role in mitigating typhoon, wave, and coastal

Completely unimportant Not important Neutral Important Extremely important

Neutral Important Extremely important