INTRODUCTION
Background
The outcomes of the 26th United Nations Climate Change Conference (COP26) in Glasgow were deemed insufficient to limit global temperature rise to the 1.5 degrees Celsius target established by the Paris Agreement, with current national policies projected to result in a 2.7 degrees Celsius increase by the century's end Even full implementation of Nationally Determined Contributions (NDCs) would still lead to a 2.4 degrees Celsius rise Despite hypothetical scenarios of halting all human-induced emissions, the effects of climate change would linger for centuries due to existing greenhouse gas levels The IPCC's 6th Assessment Report emphasizes that achieving net-zero global CO2 emissions is crucial to stop global warming Vietnam, joining over 130 countries, has pledged to reach net-zero emissions by 2050, necessitating robust policies and action plans to meet this ambitious goal amidst ongoing climate challenges.
To achieve the ambitious goals outlined in the Paris Agreement, it is crucial to establish a balance between anthropogenic greenhouse gas emissions and their removals (United Nations, 2015) However, the historical cumulative CO2 emissions from 1850 to 2019 have reached approximately 2,390 (± 240) GtCO2 (Delmotte et al., 2021), leading to a rapidly diminishing carbon budget With a 67% probability, the remaining carbon budgets to limit global warming to 1.5°C and 2°C are estimated at 400 GtCO2 and 1,150 GtCO2, respectively Currently, global CO2 emissions stand at around 40 GtCO2 per year (Friedlingstein et al.).
Urgent deep and rapid decarbonisation is essential to uphold the Earth's carbon budget and stabilize global surface temperatures Consequently, all effective mitigation strategies aimed at achieving our climate goals depend on the implementation of carbon dioxide removal methods.
Carbon Dioxide Removal (CDR) is crucial for emissions reduction, as it involves the removal of excess CO2 from the atmosphere through human activities and its long-term storage in geological, terrestrial, or oceanic reservoirs, as well as in various products CDR methods are typically divided into two main categories: nature-based options, which enhance biological production and storage in land and marine environments, and technological options, which involve advanced geochemical processes and chemical methods for CO2 management.
While technological carbon sequestration methods have the highest potential and longest storage timescales, they often require significant energy and capital, leading to various trade-offs (Arias et al., 2021) In contrast, nature-based solutions are currently viewed as the most cost-effective and viable options, providing additional co-benefits despite their limited long-term effectiveness (Erbach & Victoria, 2021) Proper restoration of vegetated coastal ecosystems, or blue carbon ecosystems, can yield advantages that go beyond mere carbon mitigation (Pửrtner et al., 2019).
Literature review
Being the largest carbon sink in the world, the ocean is absorbing over 25% of the total
Coastal ecosystems such as mangroves, salt marshes, and seagrasses, which occupy less than 0.5% of the seabed, play a crucial role in carbon sequestration, contributing to over half of the carbon stored in marine sediments However, these vital ecosystems are rapidly degrading at a rate of 2-7% annually, with significant losses of up to 67% of historical global mangroves, 35% of salt marshes, and 29% of seagrasses Without intervention, projections indicate that an additional 30-40% of salt marshes and seagrasses, along with nearly all unprotected mangroves, could vanish within the next century This degradation poses a serious threat to carbon stocks, potentially releasing carbon dioxide back into the atmosphere and exacerbating climate change, while also increasing the vulnerability of coastal communities and global biodiversity The concept of "blue carbon," introduced by the United Nations Environment Programme in 2009, highlights the importance of preserving these ecosystems for their ecological and climate benefits.
Coastal blue carbon research emphasizes the significance of vegetated habitats such as mangroves, salt marshes, and seagrasses in carbon sequestration, as highlighted in the IPCC's latest assessment report These ecosystems exhibit high productivity, with carbon burial rates of 218 ± 24 g C m -2 yr -1 for salt marshes, 226 ± 39 g C m -2 yr -1 for mangroves, and 138 ± 38 g C m -2 yr -1 for seagrasses, making them over 50 times more efficient than temperate forests Human activities play a crucial role in managing these coastal ecosystems, as they can either enhance or diminish blue carbon storage through protection, restoration, or degradation efforts.
Marine plants differ from terrestrial plants in that they cannot directly fix atmospheric CO2; instead, CO2 must first dissolve in seawater through complex physicochemical processes, which significantly affect absorption rates (Kuwae & Hori, 2019) Additionally, blue carbon stocks are impacted by various factors, particularly the changes in sediment and organic carbon due to tidal flows, including processes like burial, trapping, and loss (Figure 1.1) With proper maintenance and conservation, the organic carbon trapped in blue carbon sediments can be stored on-site for centuries or even longer (Kuwae & Hori, 2019).
In 2009, Nellemann et al laid a crucial groundwork for blue carbon research, highlighting the significant carbon capture capabilities of marine organisms and their essential contribution to various non-carbon ecosystem services They proposed key policy recommendations aimed at the protection, management, and restoration of vital ocean carbon sinks, including the establishment of a global blue carbon fund.
Established in 2011, the Blue Carbon Initiative is an international partnership between the United Nations and non-governmental organizations aimed at addressing climate change through the conservation of blue carbon ecosystems.
Restoring global coastal marine ecosystems is crucial for climate action, as highlighted by the Scientific Working Group's manual on measuring blue carbon stocks and flux (Howard et al., 2014) The Policy Working Group emphasizes the need for countries to prioritize coastal wetlands in their Nationally Determined Contributions (NDCs) (Thomas et al., 2019) Strong political commitment to blue carbon ecosystems can enhance financing, policy frameworks, and scientific efforts necessary for their restoration and sustainable management, ultimately benefiting both climate mitigation and adaptation while supporting human well-being.
Figure 1.1: Accumulation of Blue Carbon Stocks in the Coastal Ecosystems (Lovelock
To effectively promote the inclusion of blue carbon ecosystems in climate strategies, it is essential to accurately quantify their carbon stock and potential emissions This carbon inventory serves as a crucial tool for decision-makers to evaluate whether the conservation benefits of these ecosystems outweigh the associated costs (Siikamọki et al., 2014) However, significant knowledge gaps persist, complicating the estimation and valuation of blue carbon ecosystems Key challenges include limited data on the geographical extent of carbon sequestration and storage rates in salt marshes and seagrasses, human-induced emissions from ecosystem degradation, and the impacts of climate change, such as sea-level rise and coastal erosion.
The Kyoto Protocol, ratified in 1997 and came into effect in 2005, introduced the concept of “carbon credit”, which allows market mechanisms that motivate
To promote eco-friendliness and maintain global carbon emissions within acceptable limits, organizations can engage in carbon credit trading A carbon credit is a tradable certificate that allows the emission of one tonne of carbon dioxide or equivalent greenhouse gases There are three primary sources of carbon credits: emissions reductions through energy efficiency, emissions removal via carbon dioxide removal (CDR) techniques, and emissions avoidance through the protection and conservation of forests Similarly, commitments to protect, restore, and conserve blue carbon ecosystems can be traded on the global market, allowing organizations to offset their emissions elsewhere.
The UNFCCC established essential frameworks and tools for the functioning of two primary carbon market types: the compliance or regulatory market, which employs cap-and-trade schemes, and the offsetting market, which utilizes baseline-and-credit mechanisms (CMW, 2019).
Blue carbon credits are an innovative and effective means of financing the restoration and upkeep of coastal wetland ecosystems Various funding strategies exist to support blue carbon initiatives that can produce these valuable credits.
Table 1.1: Different funding approaches to blue carbon activities (Thomas S , 2014)
Activity Can occur in a developing country
Can occur in a developed country
Bi- and multi-lateral activities
Activity Can occur in a developing country
Can occur in a developed country
(including insurance, microfinance, and green bonds)
Current carbon markets inadequately reflect the social benefits of blue carbon credits, with these nature-based solutions receiving only 3% of global climate investment (Verra, 2019) Challenges in validating and verifying these credits hinder their viability as market commodities (Thomas S., 2014) However, the release of the first blue carbon conservation methodology by Verra in September 2020 marks a significant advancement, recognizing blue carbon conservation and restoration as an official project type (Verra, 2020) This development could pave the way for increased financing and market expansion for blue carbon activities.
To effectively harness the value of blue carbon credits, establishing a Global Blue Carbon Market may be essential for generating direct economic benefits through the protection of coastal ecosystems.
The cost-benefit analysis (CBA) originated in 18th century France, where Abbé de Saint Pierre proposed that enhanced trade and lower transportation costs could lead to significant benefits A century later, Jules Dupuit laid the groundwork for CBA by measuring consumer surplus Despite their contributions, these foundational ideas received little recognition in France and globally.
The principle of Cost-Benefit Analysis (CBA) was officially recognized in the United States with the Flood Control Act of 1936 In 1950, the Green Book provided further clarification on CBA concepts and introduced various market-based valuation methods for its application (Jiang & Marggraf, 2021).
Cost-Benefit Analysis (CBA) is a method used to evaluate the monetary gains and losses of an action, investment project, or policy When the benefits outweigh the costs, the initiative is likely to be effective (Hanley & Barbier, 2009) The UNFCCC recommends CBA for climate actions, as it provides evidence-based support for policymakers and stakeholders in the decision-making process, while considering social well-being factors (UNFCCC, 2011).
Research overview
At COP26, Vietnam prioritized climate change response and nature restoration in its development decisions, with key outcomes including a pledge for net-zero emissions by 2050 and endorsement of the Declaration on Forests and Land Use This highlights the importance of sustainable forest management in climate adaptation and mitigation, as well as the preservation of ecosystem services To achieve these goals, Vietnam must update its Nationally Determined Contributions (NDC) and develop detailed strategies and action plans, assigning specific tasks to various ministries.
Vietnam's 2020 Nationally Determined Contribution (NDC) highlights the significance of protecting, restoring, and planting mangrove forests as part of its adaptation strategies and acknowledges their role in carbon stock for mitigation However, the concept of "blue carbon" and the coastal ecosystem were not specifically addressed as measures for achieving greenhouse gas (GHG) reductions.
Vietnam has experienced significant mangrove losses, particularly highlighted by 2021 statistics (Spalding & Leal, 2021) By 1997, over half of the country's mangrove forests had been destroyed due to the use of herbicides and napalm during the war, as well as the conversion of land for shrimp ponds, salt ponds, and paddy fields in the years following the conflict.
Vietnam's natural mangrove forests have nearly vanished, leading to a predominance of low-diversity "planted mangroves" (MONRE, 2014) The degradation of seagrass habitats, driven by natural disasters, land reclamation for aquaculture, and coastal development, has also been significant, with complete seagrass loss reported in Quang Ninh and Hai Phong (Vietnam Environmental Protection Agency, 2005) This decline in coastal ecosystems has severely impacted marine biodiversity and adversely affected the livelihoods of coastal communities.
Blue carbon science is an evolving field focused on understanding the impact of climate change on carbon sequestration in blue carbon ecosystems Key research questions include how disturbances affect burial rates, the global extent and temporal distribution of these ecosystems, and the factors influencing carbon burial rates Studies also investigate carbon flux between blue carbon ecosystems and the atmosphere, the effects of organic and inorganic carbon cycles on this flux, and methods for estimating organic matter sources in blue carbon sediments.
Extensive research highlights effective management practices for enhancing blue carbon sequestration and storage (Luisetti et al., 2011; Bolam & Whomersley, 2005; Plan Vivo, 2013) Efforts have been made to resolve the uncertainties surrounding the valuation of blue carbon ecosystems, a key factor contributing to the controversy of blue carbon (Ricart et al., 2015; Oreska et al., 2017; Abdolahpour et al., 2018).
In Vietnam, research on blue carbon is still emerging, with a focus primarily on carbon stocks in mangroves and soils (Truong et al., 2021; Pham et al., 2020; Nguyen P T., 2016) However, the sequestration potential of tidal salt marshes and seagrass meadows remains underexplored While there have been efforts to estimate the value of ecosystem services provided by forests and mangroves (Khai et al., 2021; Nguyen et al., 2020; Vo et al., 2015), connections to the development of a carbon market are currently lacking.
This pioneering research aims to evaluate the value of blue carbon credits by conducting comprehensive greenhouse gas (GHG) inventories that assess carbon storage and sources, alongside the valuation of additional ecosystem services Furthermore, it will analyze the feasibility of blue carbon credits in Vietnam by comparing the benefits derived from these credits with the costs associated with their protection, restoration, and conservation.
To implement COP26 commitments, Vietnam will review forest carbon credit exchange projects, focusing on credits that align with its GHG emissions reduction goals, uphold rights, and promote forest development investments This effort will coincide with the establishment of carbon pricing tools, the development of a domestic carbon market, capacity-building initiatives for market participation, and non-market mechanisms as outlined in Article 6 of the Paris Agreement Properly pricing blue carbon credits will aid policymakers in integrating blue carbon into climate change mitigation and adaptation strategies, while also helping investors recognize the broader local benefits of their investments.
Vietnam is actively engaging in forest carbon credits trade agreements, including the Emission Reductions Payment Agreement (ERPA) with the Forest Carbon Partnership Facility (FCPF) and a letter of intent from COP26 with the Organization for Forest Financing (Emergent) Additionally, Vietnam is developing a proposal with the Korea Forest Service (KFS) The ERPA focuses on six northcentral provinces, while the LEAF Coalition targets the southern and highland provinces, and the KFS proposal aims to encompass twelve mountainous provinces.
The domestic carbon market in Vietnam is still evolving, with the legal framework posing significant challenges to carbon credit trading The absence of flexible mechanisms that respond to market supply and demand makes it difficult to accurately assess the value of carbon credits, particularly blue carbon credits.
Coastal Vietnam boasts a remarkable 3,260 km shoreline, 3,000 near-shore islands, and over 100 estuaries, contributing to its rich biodiversity and diverse wetland ecosystems (Mai et al., 2008) Spanning more than 10 million hectares, wetlands are found in key regions such as the Red River Delta and Mekong River Delta, as well as lagoons, mudflats, estuaries, and tidal areas from Mong Cai to Ha Tien (Thao, 2018) Additionally, south-central Vietnam is home to significant coral reefs and seagrass meadows, further enhancing the region's ecological value (Vietnam Environmental Protection Agency, 2005).
Rapid development is exerting significant pressure on ecosystems, particularly seagrass beds, which are shrinking due to natural disasters, aquaculture pond reclamation, and coastal construction In Vietnam, statistics reveal a concerning decline in seagrass coverage, with estimates showing a decrease of 40-70% (MONRE).
2014) From 1943 to 2013, Vietnam lost approximately 60% of its natural mangroves to war, degradation, and land conversion for agriculture and aquaculture use (Spalding & Leal, 2021)
The Mekong River Delta (MRD) in Vietnam, encompassing 12% of the country's natural area, is home to over 17 million people and contributes approximately 30% to the national GDP This region is vital for biodiversity and food security, supporting the largest and richest wetland ecosystems in Vietnam, which include 70% of the nation's seagrass meadows and 90% of its mangroves Spanning more than 4.9 million hectares, MRD wetlands are categorized into inland and coastal types; inland wetlands feature floodplain paddy fields, seasonally flooded grasses, and Melaleuca forests, while coastal wetlands are predominantly characterized by mangrove forests.
This research focuses on the blue carbon ecosystem, specifically the coastal wetland areas of the VMRD, located along the East Sea coastline, southwest of the Ca Mau Peninsula, and the Gulf of Thailand Over half of this region consists of permanently flooded wetlands in areas less than six meters deep at low tide, while the remainder experiences seasonal flooding The predominant coastal wetland types include unvegetated saltwater wetlands and seasonal wetlands used for agriculture and aquaculture (Vietnam Environmental Protection Agency, 2005) Mangrove ecosystems are crucial for biodiversity and ecosystem services, yet they have faced significant degradation due to war, firewood collection, agricultural clearing, and recent shrimp farming activities (Thu & Populus, 2006) Additionally, coastal swamps and marshes are found in the Long Xuyen Quadrangle, encompassing parts of Kien Giang, An Giang Provinces, and Can Tho City Seagrass ecosystems, particularly around Phu Quoc National Park's island clusters, feature extensive beds of healthy Enhalus acoroides and Thalassia hemprichii, which are vital for supporting fish populations and providing nutrition for dugongs and sea turtles (IUCN).
Climate change in the Vietnamese Mekong River Delta
MATERIALS AND METHODOLOGIES
Data collection and materials
Data on Vietnam's mangrove forests, tidal marshes, and seagrass meadows are derived from the Mekong Delta forest map available on the Coastal Protection for the Mekong Delta (CPMD) portal, in accordance with the relevant decision.
In accordance with No 594/QD-TTg dated April 15, 2013, the map was developed from forest inventory and statistics, gaining approval from relevant Provincial People’s Committees between 2014 and 2015 The shapefile was analyzed using QGIS software version 3.16.1, measuring areas of mangroves, mudflats, and seagrasses Results were verified through various sources, including the World Conservation Monitoring Centre database, literature reviews, and expert consultations While mangrove data is regularly updated, specific data on mudflats, tidal marshes, and seagrasses is scarce Therefore, to maintain data consistency, only information derived from CPMD will be utilized in this research.
All calculations will rely on secondary data sources, with essential literature including the Blue Carbon Initiative's manual, which outlines methods for assessing carbon stocks and emissions in coastal blue ecosystems (Howard et al.).
The article reviews several key sources related to wetland greenhouse gas inventories, including the IPCC's 2013 supplement to the 2006 Guidelines, and technical guidelines for coastal protection in the Mekong Delta It highlights research on the status of wetlands in Vietnam, focusing on mangrove species, as well as international studies on saltmarshes and seagrasses The evaluation of ecosystem services is emphasized, particularly regarding indirect use values at various scales Additionally, the article discusses recent analyses of land-use changes, socio-economic factors, and shrimp farming efficiency based on data from the General Statistics Office, alongside relevant news and articles.
Methodologies
2.2.1 Valuation of blue carbon credits
The valuation of blue carbon credits in the VMRD will be determined by three key factors: the carbon storage capacity measured in CO2 pools per hectare annually, the CO2 equivalent emissions resulting from land use and land cover changes, and the anticipated market prices for carbon.
The carbon stock in the Mekong River Delta, Vietnam, is assessed by evaluating the total areas of mangroves, mudflats, and seagrasses, encompassing both soil and vegetative pools within these coastal ecosystems.
Mangrove carbon pools can be classified into four pools (Howard et al., 2014) :
- Above-ground living biomass that accounts for up to 21% of the total carbon stock (trees, scrub trees, lianas, palms, pneumatophores);
- Aboveground dead biomass (litter, downed wood, dead trees);
- Below-ground living biomass (roots and rhizomes); and
- Soil carbon, this main pool includes the dead below-ground biomass and accounts for up to two-thirds of the total ecosystem carbon pool
Due to limited access to comprehensive data on mangrove carbon pools, a representative carbon storage capacity value was chosen based on its importance to the overall carbon stock and applied across the entire MRD.
Tidal salt marsh carbon pools area comprised of (Ibid.):
- Aboveground living biomass (shrubs, grasses, herbs, etc.);
- Below-ground living biomass (roots and rhizomes); and
- Soil carbon, where the majority of carbon is stored
Saltmarshes are dynamic ecosystems that are continuously evolving, influencing and being influenced by local geomorphological and physical processes Due to their interconnected nature, it is challenging to distinguish between different saltmarsh pools, leading to their consideration as a single entity The organic carbon storage capacity of a comparable national tidal marsh was utilized for calculations in this context.
Seagrass carbon pools can be divided into three main pools (Ibid):
- Above-ground living biomass (seagrass leaves and epiphytes)
- Below-ground living biomass (roots and rhizomes); and
- Soil carbon is also the largest pool
The assessment focuses solely on soil carbon stock, as below-ground living biomass constitutes only 0.3% of the total carbon pool, while above-ground biomass is too variable to consider In the Vietnamese Mekong River Delta, seagrass ecosystems are exclusively located in Kien Giang province around Phu Quoc Island Consequently, a regional organic carbon storage coefficient was applied to estimate the total carbon stock in seagrass meadows.
The blue carbon ecosystem plays a crucial role as a carbon sink, sequestering carbon and highlighting the risk of substantial greenhouse gas (GHG) emissions if disturbed (Alongi D M., 2018) To effectively assess the impact of blue carbon ecosystems on climate change mitigation, it is essential to consider not only the area of these ecosystems and the carbon stored within them but also the carbon that is emitted or sequestered (Howard et al.).
The 2013 Supplement to the 2006 IPCC Guidelines for National GHG Inventories provides essential guidance for calculating carbon stock changes in coastal wetlands through the Gain-Loss method This method involves assessing the difference in carbon stock between two points in time, T1 and T2, by utilizing activity data that indicates carbon stock gains and losses (Howard et al., 2014).
Change in carbon stock (Mg C) between T1 and T2 = Carbon stock at T1 – (carbon losses (land-use change, natural disasters, erosion, etc.) + carbon gains (soil accretion, growth, restoration, etc.))
This research focuses on calculating land-use changes resulting from drainage activities that convert land to agricultural use, aquaculture practices, and rewetting efforts that transform agricultural and aquaculture land back into mangrove ecosystems The study will utilize default emissions factors for each of these activities to assess their environmental impact.
19 to estimate the total carbon sequestration/ emissions for a certain period and the annual sequestration/emissions rate
Table 2.1: Annual emission factors associated with activities within wetlands
Activity Ecosystem EF Unit 95%CI 2 Range n
Drainage on aggregated organic and mineral soils
Aquaculture Mangroves, tidal marshes, and seagrass meadows
Rewetting on aggregated organic and mineral soils at initiation of vegetation reestablishment
1 (Camporese, et al., 2008; Deverel & Leighton, 2010; Hatala, et al , 2012; Howe, et al., 2009; Rojstaczer & Deverel, 1993)
3 (Hu, et al., 2012; Hargreaves, 1998; Nelson & Cox, 2013; Hu, et al., 2013; Kampschreur, et al., 2008; Ahn, et al., 2011)
4 Negative values indicate removal (i.e accumulation) of C
5 (Breithaupt, et al., 2012; Chmura, et al., 2003; Fujimoto, et al., 1999; Ren, et al., 2010)
6 (Anisfeld, et al., 1999; Cahoon, et al., 1996; Callaway, et al., 1997; Callaway, et al., 1996; Callaway, et al., 2012; Chmura & Hung, 2004; Craft, 2007; Hatton, et al., 1983; Kearney, et al., 1991; Markewich, et al., 1998)
Nitrous oxide (N2O) emissions were converted to carbon dioxide (CO2) equivalent using a conversion factor of 298, indicating that the release of 1 kg of N2O is comparable to emitting 298 kg of CO2 into the atmosphere.
Vietnam is set to implement a pilot carbon market by 2025, with full functionality expected by 2028, as outlined in Decree 06/2022/ND-CP on greenhouse gas emissions mitigation and ozone layer protection The primary mechanism for this market will be an emissions trading scheme (ETS), overseen by the Ministry of Natural Resources and Environment, which will be responsible for certifying carbon credits and emission permits within the domestic carbon market.
Carbon prices differ significantly across countries, with values ranging from as low as US$0.42 to nearly US$130.00 per tonne of CO2eq In the UK, the carbon price under the Emissions Trading System (ETS) typically ranges from US$0.50 to US$98.99, while Uruguay's carbon tax varies between US$0.42 and US$137.30 This research examines two types of carbon prices: the lowest feasible price, which ranges from US$1.85 to US$3.86/MgCO2 based on Vietnam's National Determined Contributions, and a second price that reflects the social costs of carbon, set at US$51/MgCO2 with a 3% discount rate.
Assessing the viability of blue carbon credits in Vietnam's Mekong River Delta requires an evaluation of their efficiency in creation A straightforward cost-benefit analysis was conducted in five steps, comparing the costs and benefits across various scenarios.
Step 1: Identification of policy options
Option 1 (extreme): Blue ecosystems are maximally exploited, protection and restoration policies are not available, and eventually all mangroves are converted into land used for shrimp farming
Option 2: Blue carbon protection and restoration are integrated into the local socio- development strategies
Step 2: Identification and putting monetary values on costs and benefits associated with each option
Option 1: The average costs and benefits of shrimp farming using the traditional methods, at the household level, of three provinces in the MRD (Soc Trang, Bac Lieu,
The Assessment Report by GIZ (Henriksen & Ngo, 2020) highlights the current status of shrimp farming technologies in Ca Mau, presenting two scenarios for investment in shrimp culture development: one where enterprises take the lead and another where communities or households invest However, this approach does not yield any additional social benefits.
Option 2: The costs and benefits of blue carbon ecosystem restoration and protection were calculated as specified in Sections 2.2.1 and 2.2.2 of this research The value of blue carbon, in particular, was estimated using a determined carbon price, selected through a literature review of current research and reports on the national and international carbon market This process further classified this policy option into two
(02) sub-scenarios, where (1) the carbon price includes its social costs was applied, and
(2) a feasible and acceptable carbon price, within the current context of Vietnam, was applied
Step 3: Calculation of profitability indicators
Equation (1) was used to calculate the net present value (NPV) and present value (PV):
The present value of costs (BPV) and benefits (CPV) at a specific time (t) is influenced by the discount rate (r), applied over a 10-year period to account for the growth of mangroves until they reach stability A positive net present value (NPV) signifies a profitable project, while a negative NPV suggests that the project should be rejected.
Similarly, the benefit and cost ratio (BCR) was calculated using the formula:
RESULTS AND DISCUSSION
Calculation results
3.1.1 Blue carbon ecosystems of Vietnam’s Mekong River Delta
Total areas of the coastal blue carbon ecosystems in Vietnam’s Mekong River Delta were calculated and compiled in Table 3.1
Table 3.1: Total considered areas for each type of blue ecosystem (Data on mangrove forest updated in 2020, on mudflats in 2016, and on seagrasses in 2021)
The total areas of mangroves and mudflats were initially calculated using CPMD tools, but recent data on mangroves has been updated to improve calculation accuracy (Cong, N V et al., 2021).
The CPMD tools for coastal protection lack data on seagrass areas, yet global seagrass distribution maps indicate that seagrass meadows in the Mekong River Delta (MRD) are primarily located around Phu Quoc Island in Kien Giang Province Within Phu Quoc National Park, the seagrass area is divided into a strictly protected zone, an ecosystem restoration zone, and a service-administration zone, as outlined in the Decision 06/2021/QD-UBND issued on July 2, 2021, by the Kien Giang Provincial People’s Committee, which governs the management of the Phu Quoc marine protected area and is relevant to this research.
Figure 3.1: Distribution of blue carbon ecosystems in the Vietnamese Mekong River Delta, extracted and compiled by author from (UNEP-WCMC, 2021; Groenewold &
An extensive literature review on the biodiversity of mangrove flora in the MRD has identified the dominant species of mangroves in each province, as detailed in Table 3.2.
Table 3.2: Dominant species distribution of mangroves by the province in the MRD
In the Mekong River Delta (MRD), the dominant mangrove species include Avicennia, Rhizophora, and Sonneratia Ca Mau mangroves, which comprise the largest portion of the total mangrove area, were chosen to represent the carbon storage capacity of the entire MRD mangrove ecosystem, measured in MgC ha -1.
A study conducted by Tue, Dung, and Nhuan (2014) assessed carbon storage in the mangrove forest of Mui Ca Mau National Park by measuring carbon content in above-ground and below-ground biomass, downed woody debris, and sediment Sampling was performed across various forest zones, including fringe, transitional, and interior areas The study evaluated the carbon stocks of mangrove species such as A alba, B parviflora, R apiculata, and S caseolaris, using specific gravity and carbon content measurements, alongside the planar intercept method for downed woody debris Sediment cores were analyzed at depths of 0-50, 50-100, and 100-250 cm to determine carbon pools, revealing an overall mean carbon storage of 762.0 ± 57.2 MgC ha -1 This figure is lower than that of Can Gio Mangrove Biosphere Reserve and Kien Vang Protection Forest, yet it remains three times higher than terrestrial forests and 1.6 times greater than the Gulf of Mexico’s carbon storage Despite being lower than other mangrove ecosystems in Southern Vietnam and the Asia-Pacific region, Mui Ca Mau National Park's carbon storage capacity serves as a representative coefficient for the area.
National Park accounts for one-third of the total mangrove area in Ca Mau province, and is considered the largest remaining primary mangrove forest in Vietnam
Research on the carbon storage capacity of mudflats in the Mekong River Delta (MRD) is limited due to insufficient data Mudflats, also known as tidal flats, are coastal ecosystems formed by sediments from river runoff and tidal inflows, containing 5-10% organic matter, comparable to salt marshes These ecosystems are significant blue carbon habitats, with global tidal flats estimated to store up to 0.9 PgC in the top meter of sediment, averaging 86.3 MgC ha -1 The only study estimating carbon storage in Southern Vietnam found that mudflats have an organic carbon storage capacity of 619.8 ± 24.3 MgC ha -1, which is nearly ten times that of Indonesia’s coastal mudflats and three times that of Gulf of Mexico salt marshes Variations in results can be attributed to differences in mudflat classification, soil textures, and sampling methods, as Vietnamese samples were taken from depths of 250-400 cm, unlike shallower samples used in other studies.
In Thi Nai Lagoon, Binh Dinh Province, samples from seven seagrass species were collected and divided into above-ground and below-ground biomass The organic carbon content of the seagrass was then analyzed using the Walkley-Black method, as outlined by Luong & Nga (2017).
Due to limited access to research on seagrass meadows in Vietnam, this study provides a representative estimate of carbon (C) storage for seagrasses in the Mekong River Delta, with a total C stock of 136.7 MgC ha-1 This figure is comparable to the organic carbon storage found in Indonesia’s seagrass meadows (Alongi et al., 2015) and exceeds the carbon stocks of seagrasses in the Gulf of Mexico by more than tenfold (Thorhaug et al., 2019) The geographical similarities allowed for the application of this carbon storage capacity in calculations.
The coastal blue carbon ecosystems in the Mekong River Delta, Vietnam, have been found to store significant amounts of organic carbon, with capacities of 762.0 ± 57.2 MgC ha-1 for mangroves, 619.8 ± 24.3 MgC ha-1 for mudflats, and 136.7 MgC ha-1 for seagrass meadows A comparative analysis with other blue and terrestrial ecosystems highlights the substantial carbon storage potential of these blue carbon ecosystems in Vietnam.
Figure 3.2: Nominal C storage capacity (MgC ha -1 ) of the Mekong River Delta
Figure 3.3: Comparison of blue carbon ecosystems organic C storage (MgC ha -1 )
The blue carbon stock for each type of blue ecosystem in the Mekong River Delta was determined by multiplying the total area by its organic carbon storage capacity Ca Mau Province alone accounts for over half of the total carbon stock, storing 34 million tonnes of organic carbon The remaining carbon stock is distributed relatively evenly among the other provinces, averaging 6.4 tonnes per province Notably, Tien Giang Province, despite its smaller mangrove area, retains a significant portion of the carbon stock due to its extensive mudflats.
Table 3.3: Blue carbon stock by the province of the Mekong River Delta (MgC) (Data on mangrove forest updated in 2020, on mudflats in 2016, and on seagrasses in 2021)
Mangroves (including sediment) Mudflats/Saltmarshes Seagrasses
The IPCC's conversion coefficient indicates that 1 tonne of carbon is equivalent to 3.67 tonnes of CO2 (Solomon et al., 2007) Using this coefficient, the CO2 sequestration potential of the MRD's blue carbon ecosystem was calculated to be 267,814,148 MgCO2 (72,973,882 MgC), reflecting an 18% increase compared to the total stock derived from the 2016 mangrove data.
A study by Liu et al (2020) analyzed land use and land cover dynamics in the Mekong Delta from 1979 to 2015, revealing two distinct regions of change Region I, located in the southern and eastern estuaries, experienced transformations in mangroves, aquaculture, and wasteland In contrast, Region II in the northern part of the Mekong Delta saw changes in forest areas (excluding mangroves) and unused land.
Figure 3.4: LUCC maps of the MRD from 1979 to 2015 (Liu, et al., 2020)
Data on LUCC from mangrove forests to planting land and aquaculture, as well as from other land-use purposes to mangroves were summarised in Table 3.4
Table 3.4: Mangrove-related LUCC in the VMRD from 1979 to 2016 (in ha)
Other land-use to Mangroves
Other land-use to Mangroves
The IPCC classifies coastal wetland management activities, categorizing agriculture as a drainage activity, aquaculture as an extraction activity, and the conversion of other land uses to mangroves as rewetting, revegetation, and creation activities (Hiraishi et al., 2014) These activities significantly impact CO2 emissions and removals, with Tier 1 emission factors (EF) utilized to assess emissions resulting from land-use and land-cover change (LUCC) within the mangrove ecosystem.
Table 3.5: Annual emission factor associated with the classified activity, adapted from
Activity EF Unit 95% CI Range n
Agriculture 7.9 MgC ha -1 yr -1 5.2, 11.8 1.2-43.9 22 Aquaculture 0.00169 KgN2O-N per kg fish produced
To assess the annual productivity of aquaculture from 1995 to 2015, data on total aquaculture area by province and overall production were obtained from the General Statistics Office.
Table 3.6: Aquaculture productivity in the Mekong River Delta
Accordingly, the annual mean aquaculture productivity used for emissions calculation is 1,780 ± 963 kg ha -1 yr -1
Using the Gain-Loss method as specified in Section 2.2.1.2, the emission/removal calculation results of the amount of CO2eq are presented in Table 3.6
Table 3.7: CO2 emission/removal from LUCC activities in the mangroves of MRD
Other land-use to Mangroves
Total blue carbon emissions from 1989-2015 is estimated at 1,664,346,263 MgCO2, and the annual emission rate is 46,231,841 MgCO2 yr -1 , or 740.19 MgCO2 ha -1 yr -1
3.1.4 Valuation of blue carbon ecosystem services
Data on the provisioning services of mangrove ecosystems in Vietnam, specifically in Ca Mau Province, were gathered from various studies These values were adjusted for comparability by utilizing the annual Consumer Price Index (CPI), highlighting the significant economic contributions of these ecosystems.
35 resources, in monetary terms, that the local communities can directly benefit from the MRD mangroves were aqua products
Table 3.8: Provisioning values of the mangrove ecosystems (US$ ha-1yr-1, 2010)
Year Timber Firewood Seafood harvesting
Discussion
The coastal blue carbon stocks in the VMRD are estimated at nearly 73 million MgC across 115,462 hectares, ranking among the highest globally for blue carbon ecosystems (UNESCO, 2020) Notably, two-thirds of these stocks are concentrated in the southern provinces of Ca Mau and Kien Giang, highlighting their crucial role in maintaining Vietnam's coastal blue carbon ecosystems Interestingly, Kien Giang, despite having a relatively small area of mangroves, contributes significantly to carbon stocks due to its extensive seagrass meadows.
Human activities significantly impact the dynamics of blue carbon ecosystems A study of land use and land cover changes in the VMRD over 37 years, from 1979 to 2015, revealed a total emission of over 1.6 billion MgCO2eq, averaging substantial carbon dioxide equivalents per year.
Aquaculture activities contribute nearly 99% of the total CO2eq emissions from land use and land cover change in the VMRD, amounting to 46 million MgCO2eq per year This significant emission level highlights the need for assessing the sustainability of previous development trends and emphasizes the importance of developing and implementing more efficient land-use management strategies.
To effectively assess the mitigation and adaptation potential of the VMRD blue carbon ecosystem, it is essential to quantify both the greenhouse gas emissions and removals associated with changes to these ecosystems, in addition to estimating their carbon stock.
Although the initial investment cost for mangrove restoration and plantation is significantly higher at approximately US$9,347 per hectare, the long-term benefits quickly surpass these costs The advantages of VMRD blue ecosystems are estimated at US$7,856 per hectare per year, or up to US$82,186 per hectare annually, depending on the carbon credit price, highlighting the economic viability of investing in coastal protection through mangrove restoration.
45 ecosystems were estimated at US$765 million in the low-price scenario or up to US$11.2 billion in the highest-price scenario 1
The Cost-Benefit Analysis (CBA) revealed that, across all scenarios and policy options, the benefits consistently outweighed the costs Notably, the advantages derived from restoring and protecting mangrove ecosystems, as well as the broader blue ecosystem, significantly surpassed those associated with other shrimp culture development scenarios Regardless of the discount rate applied, the restoration and protection of mangroves proved to be highly cost-effective, generating additional social benefits that extend beyond the parameters of this research.
The valuation of blue carbon ecosystems in Vietnam faces significant uncertainties due to factors such as coastal wetland classification, organic carbon measurement methods, ecosystem service selection, and carbon pricing While mudflats can serve as an alternative, their carbon storage capacity falls short of that of salt marshes Additionally, mudflats, tidal marshes, and seagrasses offer numerous ecosystem services beyond carbon sequestration that remain unmeasured Although the potential for a blue carbon market in Vietnam is highlighted by current carbon pricing, it fails to capture the complexities associated with the existing market for this unique commodity.
1 All benefits were calculated based on 2010 price