The role of mangroves in supporting ports and the shipping industry to reduce emissions and water pollution

This report provides scientific evidence on the role of mangroves in absorbing greenhouse gases and improving water quality through analysis of monitoring data relating to the water environment in Saigon River (Ho Chi Minh City), greenhouse gas emissions from Ho Chi Minh City seaports, and greenhouse gas sequestration in Can Gio mangrove forest (Ho Chi Minh City). This document presents, for the first time, comparative results of water quality indices for 2010–2020, at monitoring points in different areas including metropolitan, seaport, mangrove forest and open coast. A correlation between carbon emissions from seaports, and the amount of carbon absorbed by mangroves in Ho Chi Minh City, was also analysed for the first time. Our findings confirmed that mangroves can support the maritime industry to reduce greenhouse gas emissions and protect the environment. These findings can assist policymakers to identify those who can financially contribute towards the environmental services that mangroves provide, enabling the effective implementation of policy around payment for forest environmental services. We also highlight the need to have further specific studies, in other areas of the country, in order to build a complete database of the ecosystem services provided by mangroves in Vietnam. CIFOR Occasional Papers contain research results that are significant to tropical forest issues. This content has been peer reviewed internally and


Executive summary
The maritime industry plays an important role in socioeconomic development, as well as in cultural and commercial exchanges at both domestic and international levels.However, increasingly greenhouse gas (GHG) emissions and environmental pollution related to maritime operations are becoming a global issue.At COP26, establishment of initiatives like zeroemission maritime routes and zero emission shipping have been supported by many countries, including the United Kingdom, the United States, Canada and Australia, through declarations like the Clydebank Declaration for Green Shipping Corridors and Declaration on Zero Emission Shipping.
One of the most important and sustainable solutions in reducing the environmental impact of maritime operations is the conservation and development of natural ecosystems, to ensure that their inherent ecosystem services -like regulating and supporting services -remain stable and can thus contribute to the absorption of environmental pollution.Mangrove ecosystems, distributed mainly in coastal estuaries and close to seaports, are known for their many important ecosystem services, including GHG absorption and improvement of environmental quality.However, such services are not widely known in the maritime industry, and have not been incorporated into current policy.This is an obstacle when it comes to identifying appropriate stakeholders and potential financial mechanisms to contribute towards the environmental services provided by mangroves.
This document provides strong scientific evidence on the role of mangroves in absorbing GHGs and improving water quality through analysis of monitoring data relating to the water environment in Saigon River (Ho Chi Minh City), greenhouse gas emissions from Ho Chi Minh City seaports, and GHG sequestration in Can Gio mangrove forest (Ho Chi Minh City).This document presents, for the first time, comparative results of water quality indices for 2010-2020, at monitoring points in different areas including metropolitan, seaport, mangrove forest and open coast.A correlation between carbon emissions from seaports, and the amount of carbon absorbed by mangroves in Ho Chi Minh City, was also analysed for the first time.
Our findings confirmed that mangroves can support the maritime industry to reduce GHG emissions and protect the environment.This document can assist policymakers to identify those who can financially contribute towards the environmental services that mangroves provide, enabling the effective implementation of policy around payment for forest environmental

Introduction
Emission Shipping by 2050 (Ministry of Industry Business and Financial Affairs 2021), signed by 14 countries, also highlights increasing efforts by global companies who are actively searching for environmental solutions to reduce the sector's emissions.
Vietnam is a country with a large sea area and a long coastline, with many straits and deep bays.
In close proximity to bustling trading routes throughout the East Sea, Vietnam spans an island system of 3,000 coastal islands that 'shield' most of the inshore marine areas and coastal areas.
Vietnam has 36 seaports, including hundreds of terminals distributed along its coast.It has set a target by 2030 and a vision until 2050 to develop a modern seaport network that meets green port criteria, fully and effectively meeting the country's socioeconomic development needs, while also acting as driving force for the development of the maritime economy (Vietnam Maritime Administration 2021a).However, along with the development and operation of seaports, waste generated from business activities, seaport and shipping operations, equipment to support shipping operations, dredging activities, the maintenance of navigational channels, anchoring areas for transhipment and areas to shelter from storms, also cause serious pollution challenges both in the air (emissions of GHGs like SO 2 , CO 2 , CO), and water (suspended and fatty pollutants), resulting also in erosion, accretion and deterioration of coastal ecosystems (Mai and Anh 2021).As such, the primary suggestion proposed for seaports at the present time, is to prevent and minimize environmental pollution by building 'green' seaports which can harmonize environmental protection with socioeconomic development objectives.In this Clydebank Declaration, countries committed to "identify and explore actions to address barriers to the formation of green corridors.This could cover, for example, regulatory frameworks, incentives, information sharing or infrastructure and work to ensure that wider consideration is taken for environmental impacts and sustainability when pursuing green shipping corridors".The Declaration on Zero There are two key aspects involved in achieving this goal: • Preventing and controlling seaport pollution, through technical solutions and improving the system for specialized agencies on seaport environmental management and regulation; • Conserving and developing natural ecosystems in seaport areas, so their inherent ecosystem services remain stable and can absorb seaport-derived environmental pollution.
One of the typical ecosystems in question is mangroves, which have the ability to absorb GHGs and store pollutants in their plants (Dunbabin and Bowmer 1992;Wood and Shelley 1999;Yu et al. 2001;Thanh-Nho et al. 2019;Hong Tinh et al. 2020;Pham et al. 2021 The study aims to provide important data on the environmental services provided by mangroves, namely carbon sequestration and the cleaning of seaport-related environmental pollution in water, so as to support future policy design regarding payments for mangrove environmental services in Vietnam.

Study site
The study was conducted in the seaport area of Ho Chi Minh City and Can Gio mangrove forest (Figure 1).Ho Chi Minh City seaport includes 42 terminals distributed along Saigon River (specifically the section flowing through the districts of Nha Be and Can Gio, about 15-30 km south of Ho Chi Minh city centre).We focus on this area as it is one of the major seaports

Data collection
Initially secondary data from published reports and statistical data was synthesized, before a spatial analysis method (using ArcGIS) was applied to conduct a comparative assessment of environmental quality in mangroves and areas with and without seaport development.

Method used to calculate water quality assessment parameters
This study used Vietnam water quality index (VN_WQI) (Vietnam Environment Administration 2019) to assess the water quality of the study site.The advantage of this index is that it quantifies water quality through parameters like pH, total organic carbon (TOC), dissolved oxygen (DO), total NH 4 + , total Nitogen (TN), total Phosphorous (TP), as well as concentration of dissolved metal ions, pesticide components and microbiological factors.This index has been used by governments and scientists around the world and in Vietnam (Thanh-Nho et al. 2020).
In this study, the VN_WQI was calculated under the guidance of Vietnam Environment Administration (2019).VN_WQI was calculated separately for each monitoring station, using monitoring data associated with five groups of parameters: To calculate VN_WQI, data needed to include a minimum of three of the parameter groups above.Group 4 was essential for inclusion in the calculation, and had to cover a minimum of three parameters for calculation.VN_WQI values were classified into six categories, as described in Table 1.

Statistical analysis method
Analysis of variance (ANOVA, T-test (Student Test)) was used to compare and access the average VN_WQI index at different monitoring locations (i.e., in the city centre, port, mangrove and coastal areas) along Saigon River.Calculation and comparison of VN_WQI in different locations helped to assess the quality of surface water at inflow locations where there were pollution sources, mangrove forests and no mangrove forests, and in locations where water flows into the sea.This meant the quality of surface water could be assessed before entering the mangrove forest and after flowing through the mangrove forest, helping us to answer the question: Can mangroves help to improve water quality and air quality in port areas?

Interpolation method and mapping
This study built a water quality zoning map showing an overview of water quality according to the average VN_WQI in the study period for each river section, based on interpolation from calculated VN_WQI data for each monitoring station.The process of making a water quality zoning map according to VN_WQI indices is summarized in Figure 2.

Figure 2. Process of building a VN_WQI -based water quality zoning map
Data used to create a water quality zoning map using VN_WQI indices consisted of two groups of data layers: (i) data for the geographic base map, and (ii) thematic data.

Geographic base map data
The geographic base map data used in the study were extracted and edited from the national geographic base map, including information layers on the administrative boundaries of provinces, water bodies and the sea boundary (Vietnam Publishing House of Natural Resources 2020).All national geographic data was standardized to the VN-2000 coordinate system, in accordance with Ministry of Natural Resources and Environment regulations, and converted using ArcGIS.

Thematic data
Locations of monitoring stations were added to the database in the form of points, and standardized according to the VN-2000 coordinate system.The attributes of VN_WQI and the location of terminals and mangroves were also included.
In this study, the inverse distance weighted (IDW) interpolation method of ArcGIS (ESRI 2021) were used to generate attribute values of VN-WQI for entire water surface area of Saigon river based on the known observations at monitoring stations.
In recent years, much attention has been paid to seaport investment and development and many policies have been issued in relation to this.Numerous entities invest in and manage the seaport system; however, the state administrative management agencies play the most critical role.Agencies undertaking management as representatives of the State include: the Vietnamese government at all levels, the National Assembly, the Ministry of Transport, the Maritime Administration, the local maritime port authorities and administrations; and The seaports are distributed along the Vietnamese coastline from Quang Ninh Province to Kien Giang Province (Figure 3).

Seaport development in Ho Chi Minh City
According to Decision No. 761/QD-BGTVN dated 24 April 2020 of the Minister of Transport, announcing the list of Vietnamese seaport terminals (Ministry of Transport 2020), Ho Chi Minh City seaport has 42 terminals, operated by various companies, including national and local state-operated military agencies and foreign maritime organizations (Table 1).Ho Chi Minh City seaport is one of Vietnam's biggest seaports, playing an important role in the country's seaport system, with a large volume of cargo passing through, accounting for more than 20% of the total cargo that passes through all of the country's seaports.The seaport's terminals Sai Gon, Ben Nghe, Tan Thuan and Sai Gon-Hiep Phuoc currently occupy the largest land area, serving both international and domestic trading activities.The terminals of Ho Chi Minh City seaport vary in size and capacity, and are run by different sectoral businesses (Table 3).
Vietnam    Port activities -including construction, access channel dredging and port operations -can generate waste that poses adverse impacts on the quality of the air and water environment (Trozzi and Vaccaro 2000).During the processes of port construction and access channel dredging, the water environment in the port area may be affected by domestic wastewater and wastewater from surface washing and machinery cleaning.
Such wastewater can increase turbidity, suspended solid waste, concentrations of heavy metals, grease and microorganisms in the port area, in both river and sea water.When the port is operational, wastewater generated from the activities of workers, crews and passengers, overflowing rainwater, bilge water, ballast water and oil-containing water, for example, are sources of pollutants that result in degradation of the 5 The impact of seaports on water quality and the role of mangroves  water environment in the port area (Stakeniene et al. 2011;Gómez et al. 2015;Catianis et al. 2016;Jahan and Strezov 2019).This not only causes negative impacts on river and coastal ecosystems, but also reduces the value of existing ecosystem services like tourism, aquaculture and fishing productivity (Trozzi and Vaccaro 2000).Barberi et al. (2021) in their literature review also confirmed the impact that shipping and port operations had on the air environment, with GHG emissions being generated by vessels entering and leaving the port, onshore energyusing vehicles like loading and unloading cranes, and cargo trucks, as well as lighting systems at the port.
Surface water monitoring data from the seaport area of Ho Chi Minh City shows that, although concentrations of most surface water quality parameters remain within the allowable limits, according to the Vietnamese Standard QCVN 08-MT:2015/BTNMT (Ministry of Natural Resources and Environment 2015), concentrations of some parameters, like TSS, DO and Fe, exceed the allowable limits (Table 5).
There is a general trend across all surface water quality parameters that concentrations are higher in the seaport area, decreasing gradually in monitoring stations further from the port terminals.Specifically, the surface water quality index (VN_WQI) decreases gradually in areas far from the port terminals (Figure 5). Figure 5 also shows that water quality, after running through mangroves, has significantly improved.
As indicated in Table 1, the higher the VN_WQI, the better the surface water quality.As Saigon

Monitoring area
River flows through Ho Chi Minh City, the surface water quality is best in the mangrove area (VN_WQI = 92.3),followed by the coastal area (VN_WQI = 88.1), and the city centre (VN_WQI = 85.1), whereas it is lowest in the seaport area (VN_WQI = 75) (Figure 6).It can be confirmed from these findings that Ho Chi Minh City seaport operations impact the quality of surface water in the Saigon River, but that the level of this impact is not high, and concentrations of most pollutants in surface water remain within allowable limits (Ministry of Natural Resources and Environment 2015); surface water quality remains at or above average level (Vietnam Environment Administration 2019).However, given the plans for further seaport development in the near future, if port environmental protection activities are not well managed, surface water quality in the seaport area of Ho Chi Minh City could become severely degraded.
Regarding GHG emissions from port operations around the world, Psaraftis and Kontovas (2021) estimated that GHG emissions (carbon dioxide equivalents -CO 2 e) increased from 977 million tons in 2012 to 1,076 million tons in 2018 (up 9.6%) with CO 2 making up almost 98% of total GHGs.Greenhouse gas emissions have also been estimated for major ports across the region and world, for example Chennai has been estimated to generate 280,558 tons/year (Misra et al. 2017), Osaka 97,000 tons/year, Sydney 95,000 tons/year, Gothenburg 150,000 tons/ year and Long Beach 240,000 tons/year (Styhre et al. 2017).Across the world and within Vietnam, many studies have been undertaken into the ecosystem services provided by mangroves (Mukherjee et al. 2014;Himes-Cornell et al. 2018;Mitra 2020;Pham et al. 2021).This includes services like cleaning up the water environment (Dunbabin and Bowmer 1992;Wood and Shelley 1999;Yu et al. 2001;Thanh-Nho et al. 2019;Thanh-Nho et al. 2020) and absorbing GHGs from the air (Clough et al. 2000;Tue et al. 2014;Nam et al. 2016;Hong Tinh et al. 2020;Rovai et al. 2021).Can Gio mangrove forest in Ho Chi Minh City spans a total area of 35,000 ha, and has high biodiversity with 35 true mangrove species (Nam et al. 2014) and many other valuable mangrove fauna species (Hong 2004;Nam et al. 2014) Seaport construction and operation activities can generate waste, affecting the quality of both water and air environments in seaport areas.In general, the surface water quality of Saigon River remains at or above average levels.However, the quality of the surface water declines gradually from the city centre to the seaport area, before becoming very good in Can Gio mangrove forest, then flowing into the sea.An estimation of GHG emissions, based on 15 out of 42 terminals in Ho Chi Minh City's seaport, also shows that around 34.8 thousand tons of CO 2 e are released into the environment annually.Given the plans for marine economic development and the goal to develop the seaport system between 2021 and 2030, the environmental impact of the shipping industry in general, and seaports in particular, will continue to increase.

Seaport emissions and the role of mangroves in mitigating emissions
Mangroves have a proven ability to absorb GHGs through mangrove vegetation photosynthesis, as well as the ability to clean surface water through depositing, absorbing and accumulating pollutants in sediment and mangroves.This means that in areas where the environment is polluted by waste sources, including seaports, mangroves can act as a natural wastewater treatment system, helping prevent pollutants from discharging into the aquatic environment, and balancing greenhouse gases that have been emitted into the atmosphere from seaport operations.This is critical knowledge upon which to base any proposed solutions and policies that are intended to encourage and promote the shipping industry to participate more actively in payments for forest environmental services, thus contributing to maintaining and expanding the mangrove area, increasing Vietnam's capacity to respond to climate change, and fulfilling the country's commitment to environmental protection.

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This report provides scientific evidence on the role of mangroves in absorbing greenhouse gases and improving water quality through analysis of monitoring data relating to the water environment in Saigon River (Ho Chi Minh City), greenhouse gas emissions from Ho Chi Minh City seaports, and greenhouse gas sequestration in Can Gio mangrove forest (Ho Chi Minh City).This document presents, for the first time, comparative results of water quality indices for 2010-2020, at monitoring points in different areas including metropolitan, seaport, mangrove forest and open coast.A correlation between carbon emissions from seaports, and the amount of carbon absorbed by mangroves in Ho Chi Minh City, was also analysed for the first time.Our findings confirmed that mangroves can support the maritime industry to reduce greenhouse gas emissions and protect the environment.These findings can assist policymakers to identify those who can financially contribute towards the environmental services that mangroves provide, enabling the effective implementation of policy around payment for forest environmental services.We also highlight the need to have further specific studies, in other areas of the country, in order to build a complete database of the ecosystem services provided by mangroves in Vietnam.
CIFOR Occasional Papers contain research results that are significant to tropical forest issues.This content has been peer reviewed internally and externally.

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Figures 1
Figures 1 Map of the study site 2 Process of building a VN_WQI -based water quality zoning map 3 Map of the Vietnamese seaport system 4 Volume of cargo (million tons) passing through Vietnamese seaports during 2015-2020 5 Surface water quality (VN_WQI) in Saigon River, Ho Chi Minh City 6 Surface water quality index in different monitoring areas along Saigon River, Ho Chi Minh City 7 GHG emissions from 15 Ho Chi Minh seaport terminals, in correlation with GHG sequestration by Can Gio mangrove forest In recent years, Vietnam's seaport system has seen robust development.It has met approved planning development goals to become a driving force for economic and industrial development in urban coastal areas, by ensuring that imported and exported cargo and freight can pass between the country's regions by sea.Statistics show that 427.8 million tons of cargo passed through seaports in 2015; this accounts for 81.8% of the volume of cargo passing through all Vietnamese ports, including seaports, inland waterway ports and airports (Figure4).By 2020, the volume of cargo passing through the seaport system reached 692.3 million tons, equivalent to 78.7% of total cargo volume passing through all Vietnamese ports.During 2016-2020, the volume of cargo passing through seaports increased by 61.8%, an average increase of about 10% per year (Le Anh 2021).Some gateway seaports for international transhipment have been established in the North, like Lach Huyen port (Hai Phong) which receives container vessels of up to 132,000 DWT (deadweight tonnage) and in the South like Cai Mep seaport (Bia Ria -Vung Tau) which receives container vessels of up to 214,000 DWT.A total of 25 international shipping routes and 7 domestic sea shipping routes have been established to locations both within the country and across the globe.According to Decision 1579/QD-TTg, approving the master plan for development of Vietnam's seaport system for the period 2021-2030 with a vision to 2050 (Prime Minister 2021a), the Vietnamese seaport system will undergo comprehensive development to ensure high-quality, modern services that meet socioeconomic development, security and defence, maritime safety and environmental protection needs, enhancing economic competitiveness, and enabling the passingthrough of 1.140 to 1.423 million tons of cargo and 10.1 to 10.3 million passengers.

Figure
Figure 4. Volume of cargo (million tons) passing through Vietnamese seaports during 2015-2020 Source: Vietnam General Statistics Office (2021)

Figure 5 .
Figure 5. Surface water quality (VN_WQI) in Saigon River, Ho Chi Minh City

Figure 6 .
Figure 6.Surface water quality index in different monitoring areas along Saigon River, Ho Chi Minh City

Figure 7 .
Figure 7. GHG emissions from 15 Ho Chi Minh seaport terminals, in correlation with GHG sequestration by Can Gio mangrove forest

Table 2 . Vietnam's major seaport management activities and respective responsible agencies No. Management activities Agencies
According to the development master plan for Vietnam's seaport system, approved by the Prime Minister in Decision 1579/QD-TTg dated 22 September 2021 (Prime Minister 2021a),

Table 3 .
ContinuedThe role of mangroves in supporting ports and the shipping industry to reduce emissions and water pollution | 15

Table 5 . Surface water quality parameters in Saigon River, Ho Chi Minh City during 2011-2020
Note: * Limit values of surface water quality used for domestic water supply (Colume A1) and for waterway transportation and other purposes (column B2) (Ministry of Natural Resources and Environment 2015) Source: Ho Chi Minh City environmental monitoring reports for 2011-2020 Vietnam's seaport system has developed rapidly in recent years, becoming a driving force for socioeconomic development in coastal areas through facilitating the import, export and movement of maritime cargo between regions.Ho Chi Minh City seaport is one of the country's main seaports, with cargo volume passing through it accounting for more than 20% of the total cargo volume passing through all Vietnamese ports.Of the many entities involved in managing, investing and developing seaports, central to local-level state administrative agencies -including the Maritime Administration, the Ministry of Transport and local maritime port authoritiesare the most important.