By Professor Yu Guopei
Department of Geography
East China Normal University
Shanghai, 200062, China

Executive summary

Mangrove ecosystems represent an important component of the coastal environment by helping to protect shorelines against coastal erosion, sea storms and floods in many countries of the region. The close monitoring of such coastal resources and the facility to produce sound, integrated development plans using remote sensing and GIS technologies can assist in alleviating poverty in these areas. This project is currently being financed by the Government of France and undertaken by ESCAP under the Regional Space Applications Programme for Sustainable Development.

The project involves four countries of the region, namely China, the Philippines, Thailand and Viet Nam. The rapid degradation of mangroves over the past 25 to 40 years in each of these countries has left but a small fraction of the coastline that used to be sheltered by mangroves. Coastal zone environment management is therefore a priority, as can be observed, since several projects making use of remote sensing and GIS technologies have already been carried out by a number of national agencies, including the four agencies designated for this project.

The project aims to facilitate the regular updating and detailed surveying of coastal areas at a scale of 1:50,000 or larger, through the adoption of a common methodology and the use of common formats for the exchange of data and results. It is expected that such an approach would constitute a useful TCDC mechanism between the participating countries and a progressive leveling of disparities in their capacity to carry out integrated coastal zone development planning.

The first phase of the project consisted of an initial assessment study, which was carried out by a team of one consultant from the East China Normal University and one ESCAP staff member during the months of June and July 1997. The team visited the principal investigators, nominated by the respective RESAP national focal points, and their research teams in the four countries. The main objectives of the study were to assess the present status of coastal monitoring and development planning activities focusing on mangrove ecosystems using remote sensing and GIS, and to have preliminary discussions on project implementation, including the identification of suitable pilot areas in each country. The report provides an overview of the status of mangroves in each country and presents the findings of the initial study mission, in particular with respect to the status of mangrove forests, related experience, and the identification of the pilot areas.

Finally, the report also provides guidelines on the procedures/methods that should be followed by the principal investigators in producing their results. The four countries will be working together and independently following this common core methodology to produce results to be integrated in a report that will be disseminated to relevant institutions/agencies of other countries of the region confronted with coastal zone/mangrove management and protection.

Content

1. Introduction

Mangrove ecosystems are fragile and represent an important component of the coastal environment by helping to protect shorelines against coastal erosion, sea storms and floods in many countries of the region. The close monitoring of such coastal resources and the facility to produce sound, integrated development plans using remote sensing and GIS technologies can assist in alleviating poverty in these areas.

This project aims to facilitate the regular updating and detailed surveying of coastal areas at a scale of 1:50,000 or larger, through the adoption of a common methodology and the use of common formats for the exchange for data and results. It is expected that such an approach would constitute a useful TCDC mechanism between the participating countries and a progressive leveling of disparities in their capacity to carry out integrated coastal zone development planning.

The project involves four countries of the region, namely China, the Philippines, Thailand and Viet Nam, which will be working together and independently following a common core methodology to produce results to be integrated in a report that will be disseminated to relevant institutions/agencies of other countries of the region confronted with coastal zone/mangrove management and protection.

The initial assessment study was carried out by a team of one consultant from the East China Normal University and one ESCAP staff member during the months of June and July 1997. The team met the principal investigators, nominated by the respective RESAP national focal points, and their research teams in the four participating countries. The main objectives of this study were to assess the present status of coastal monitoring and development planning activities focusing on mangrove ecosystems using remote sensing and GIS, and to have preliminary discussions on project implementation, including the identification of suitable pilot areas in each country. This report also provides guidelines on the procedures/methods that should be followed by the principal investigators in producing their results.

Content

2. Current status in the participating countries

2.1 Current status in China

2.1.1 Status of mangrove forests

The mangrove forest ecosystem plays an important role in the coastal zone of China. These forests are distributed in the southern part of China, the greater part on Hainan Island, Guangxi, Fujian and Guangdon provinces. There were about 120,000 ha of mangroves along the coasts of those provinces in 1960. In the following years, particularly during the 1960s and 1970s, mangroves were subjected to massive destruction and, according to estimations, two thirds have disappeared, including, more specifically, 50 per cent in Fujian, 52 per cent in Hainan, 66 per cent in Guangxi and 88.5 per cent in Guangdon.

In the 1980s, the Government of China established, in an effort to protect mangrove forests and their ecological environment, 11 natural mangrove conservation areas, four of which are national conservation areas. The 11 areas comprise a total of 20,000 ha, including 7,000 ha, of forest area.

2.1.2 Major current projects related to coastal zone environment management

The Research Center is currently working on a number of major national and international projects including the following:

• Regional programme for the protection and management of marine pollution in the East Asian Seas, Xiamen demonstration site. Financed by UNDP/IMO/GEF;
• Marine pollution studies using remote sensing. Financed by the National Defense and Technology Council;
• Undersea topography research in South China Sea using SPOT satellite remote sensing technology. Financed by the National Nature and Science Fund.

2.1.3 Pilot area

The Chinese research team proposed two pilot areas: a small test site located at a practical distance from the research team's office and the pilot area per se. The pilot area per se is located in Qinglan harbor, Weniang County, on Hainan Island. It corresponds to one of the national mangrove ecosystem conservation areas. Well-protected, the pilot area extends over 1,333 ha and houses the highest number of mangrove species in China. There are about 30 species of mangrove trees, 26 of which can be found in Qinglan harbor.

As Qinglan harbor. is situated over 500 km from Jimei University, a test area was proposed by the principal investigator to facilitate the testing of image processing algorithms and improve mapping precision using SPOT data. It is located in Longhai and Dongyu and covers a total surface area of 67 ha (from the latest estimate obtained in 1991).

The main reasons for selecting Qinglan harbor. as the pilot area are its large species diversity, relatively large surface area, and protected condition, as well as the large quantity of data already collected.

2.2 Current status in the Philippines

2.2.1 Status of mangrove forests

In 1918, the mangroves were estimated to cover as much as 400,000-500,000 hectares but, by 1956, this had been reduced to 327,500 ha and by 1976 to about 217,861 ha. In 1988, the remaining mangroves were estimated at between 139,000 to 149,400 ha, or 27 per cent of the 1918 figure. With the updated information on the remaining mangroves, the government passed two new laws for the preservation and conservation of a total of 78,593 ha of mangrove forests.

A recent study clearly shows that conversion to fish ponds is currently the major cause of mangrove destruction, followed by the use of mangrove areas for human settlements.

A total of 50 species of mangroves belonging to 26 families occur in the Philippines. The families Rhizophoraceae (nine species), Avicenniaceae (four species), Combretaceae (two species), Meliaceae (two species), Palmae (two species), Euphorbiaceae (two species), Aegecerataceae (two species), Rubiaceae (one species) and Sonneratiaceae (two species) are considered true mangroves and the rest as mangrove associates.

2.2.2 Major current projects related to coastal zone environment management

NAMRIA is currently involved as the main executing agency in several projects related to coastal zone environment management, including the Coastal Environment Programme (CEP) led by the Department of Environment and Natural Resources and the mangrove inventory, assessment and mapping of CEP areas (since 1993); the Coastal Zone Environment and Resources Management Project, which is part of the ASEAN-Australia Economic Cooperation Programme (since 1995); and a project to map and carry out land-cover assessment of mangrove areas with assistance from JICA (since 1997).

Recent and/or ongoing projects of the International Center for Living Aquatic Resources Management (ICLARM) include the assessment of coastal habitats in Manila Bay and in Carigara Bay, as well as resource and ecological assessment of Honda Bay in Palawan. Another interesting project carried out between 1992 and 1994 was the assessment of mangrove areas and site identification for reforestation in Lingayen Gulf.

2.2.3 Pilot area

The pilot area selected for the study, in consultation with the members of NCMS, is Ulugan Bay in Palawan Island, situated approximately 650 km south-east of Manila.

The dominant species in the mangroves of Ulugan Bay are Rhizophora apiculata, Rhizophora mucronata and Rhizophora apiculata; the dominant soil type is sand silt-mud, with pH values between 6.2 and 7.8 and salinity between 26.5 and 29.0 ppt. The average temperature in the area is 27.6°C

Ulugan Bay was selected for several reasons:

(a) It is one of the biggest mangrove areas in the country;

(b) The University of the Philippines and, in particular, Prof. Miguel Fortes currently have mangrove ecosystem-related projects in the area;

(c) Base maps already exist;

(d) Coastal zone planning and management is an important issue in areas protected for their mangroves.

2.3 Current status in Thailand

2.3.1 Status of mangrove forests

Mangrove forests in Thailand are found along muddy coastlines and in the estuaries of rivers where the soil is deep and the salinity content is high. Along the Gulf of Thailand, forests occur from Trad in the eastern region to Prachuab Kiri Khan in the central region. Along the east coast of the southern region, mangrove forests occur from Chumphorn down to Pattani and along the west coast, from Satun north to Ranong. In 1961, there were 367,900 ha of mangrove forest in the country. In the 30 years that followed, this resource was reduced by more than 50 per cent, to a total surface area in 1991 of only 173,608 ha.

According to geographic and climatic factors, mangrove forest areas in Thailand can usually be grouped into four regions:

• East Thailand (four provinces), with a coastline of about 500 km and 10,500 ha of mangrove forest;
• Central Thailand (seven provinces), with a coastline of about 440 km and about 775 ha of mangrove forests;
• South Thailand -- East Coast (six provinces), with a coastline of about 930 km and 13,980 ha of mangrove forest;
• South Thailand -- West Coast (6 provinces), the best and most developed mangrove forest areas are found in this region. The total length of the coastline is about 710 km with 148,350 ha of mangrove forests.

2.3.2 Major current projects related to coastal zone environment management

In the last ten years, at least eight remote sensing projects related to mangrove forests have been carried out by NRCT:

(a) Remote sensing and mangrove in Thailand;

(b) Integrating remote sensing and GIS for mangrove management in Thailand;

(c) Study on change of mangrove forest in Sawi Thung Kha estuary, Chumphon Province, by using satellite imagery;

(d) Application of remote sensing for monitoring the changes of mangrove forest area in Thailand;

(e) Tropical mangrove vegetation mapping using advanced remote sensing and GIS technology;

(f) Application of ERS-1 SAR data for coastal studies;

(g) Application of GIS for mangrove management;

(h) Application of remote sensing and GIS for coastal resource planning: a case study -- coastal zone of Phuket.

2.3.3 Pilot area

The pilot area selected for the study is Ao Sawi-Thung Kha. It has a total surface area of about 300 km2, 100 km2 of which is land and 200 km2 sea water; it is located between 10° 15' and 10° 30' N latitude and 99° 7' and 99° 22' E longitude, at the mouth of Khlong Sawi and Khlong Thung Kha, in Chumphon Province in the south-eastern seaboard of Thailand. This coastal zone has a tropical monsoon climate with two main seasons (wet and dry). The average annual rainfall is 2,010 mm and the mean annual temperature is 26.9°C. The tidal type of this region is diurnal with an average amplitude of 1.04 m. The present general land cover of the area is composed of mangrove forests, shrimp farms, paddy fields, mixed orchards and coconut orchards, swampy areas, and inland forests. In the past decade, mangrove forests have been destroyed primarily to make way for shrimp farming, both legal and illegal.

2.4 Current status in Viet Nam

2.4.1 Status of mangrove forests

The 3,200-km-long coastline of Viet Nam has the potential to support a substantial area of mangroves. Unfortunately, no exact records have been maintained on the area of mangrove forest existing in the entire country. Before the second Indochina war (1962-1971), it is estimated that mangrove forests covered an area of about 400,000 ha, 250,000 ha of which were found mainly in the South.

Through the two Indochina wars, which together lasted almost 30 years, the quantity, quality and composition of mangroves have changed greatly. The use of herbicides and napalm during the Viet Nam war resulted in the destruction of nearly 40 per cent of the mangrove forests in southern Viet Nam. In other areas, mangroves have been exploited for their resources or replaced by agricultural and shrimp farms.

According to statistics obtained in 1983 by the Forest Inventory and Planning Institute, the 252,000 ha of mangrove forests remaining at that time were composed mainly of secondary growth, plantations and bushes, while natural forests occupied only a small area.

2.4.2. Current major projects related to coastal zone environment management

Current related projects in the Remote Sensing Information Division (RSID) include environmental impact assessment of estuaries, forest conservation studies, the integrated survey of Camau peninsula and Long Xuyen, flood control planning of the Mekong delta, and research on mangrove ecosystems. RSID is cooperating with the Department of Science, Technology and the Environment, the Forest Inventory and Planning Institute (FIPI), the Institute of Geography, the Sub-institute of Water Resources Planning and Management and the Institute of Ecology in carrying out the above projects.

2.4.3 Pilot area

The pilot area is Can Gio, one of six districts in the periphery of Ho Chi Minh City (HCMC). Can Gio extends over 680 km2 and has a population of 58,863 inhabitants (according to statistical data of 1993). Can Gio is one of the two protected mangrove areas in HCMC.

Three decades ago, mangrove forests covered all of Can Gio District and much of the land to the west of what was then National Road N51. Mangrove reforestation efforts began in 1975 and continue to this day. At present, about 21,000 ha in Can Gio District have been replanted and 9,000 ha have been allowed to generate naturally.

The topography is simple and flat with a slope of less than one degree. Mean temperature ranges from 25.7 to 28.8°C. The annual rainfall ranges from 1,300 to 2,100 mm. All the rivers and canals inside HCMC are affected by an unequal semi-diurnal tidal regime with a tidal amplitude ranging from 0.3 to 3.5 m.

There are 32 mangrove species growing in the Sai Gon River estuary/Ba Rial/Vung Tau area: Bruguiera gymnorrhiza, Acgiceras spp. Ceriops spp., etc. The mangrove in the area, particularly in Can Gio District, Rhizophora apiculata; have been recently affected by upstream industrial pollution. An oil spill from a ship in the Long Tau River in 1994 damaged the mangrove plantations growing in the north part of the district.

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3. Proposed methodology

One of the important objectives of the project is the definition of a methodology that can be followed by the four project teams and, at the same time, can be adapted to the specific conditions of the four study areas. This is meant, in particular, to set up the basis for increased cooperation among the four designated agencies in tackling important coastal zone environment management issues. It will also be useful for the construction of the integrated report, which is another important objective of this project.

The report will contain the results of the pilot studies carried out by the four participating countries and would be eventually disseminated to relevant institutions/agencies of countries of the region confronted with coastal zone/mangrove management and protection, including Bangladesh, Fiji, India, Indonesia, the Islamic Republic of Iran, Malaysia, Pakistan and Sri Lanka.

The major aims of the report are the following:

(a) illustrate the usefulness of remote sensing and GIS technologies for:

• The monitoring of changes in mangrove ecosystems;
• Coastal zone environment management and sustainable natural resource development (including the updating of existing information on coastal zone environments and resources);

(b) Promote data/information exchange among participating countries in an effort to increase regional cooperation;

(c) Assist in further capacity-building of developing countries of the region in coastal zone/mangrove management and protection through the distribution of the report to coastal zone/environment management agencies in those countries.

Although some coastal zone environment management problems in the participating countries may differ and therefore require different types of data processing/analysis, a basic or core methodology needs to be followed to ensure data comparability and compatibility and facilitate the integration of the data/information from different environmental and socio-economic sectors to be included in the report. A common core methodology and set of guidelines to carry out the four pilot projects will also result in a more meaningful product.

The components of the methodology presented below refer to the nature of the contents of the digital database, the structure of the database files, and data exchange formats. More detailed information on details of digital image processing and GIS analysis will be discussed during the meeting of principal investigators.

3.1 Contents of the databases for the pilot areas

Some data are fundamental to nearly any environmental management issue. These include the basic topography, climate, soil, land cover, infrastructure such as roads, and administrative subdivisions. These form the foundation upon which environmental management decisions are usually based.

The suggested contents of the digital databases to be constructed for each pilot area, and eventually included in the report, comprise base maps, satellite imagery in various forms, various types of point data, ground truth photographs and text. These are described in the following paragraphs. A flowchart of the various types of data to be found in the database is provided in figure 1.

3.1.1 Base maps

Base maps, already in digital format, will be included in the database after conversion, if necessary, into Arc/Info format. Other useful maps in analogue format will need to be digitized accordingly. The data layers, which can be obtained from base maps, that will make up the database include:

• Administrative boundaries (political and forest/environmental related protected areas) (1:50,000 or larger)
• Elevation contours (1:50,000 or larger)
• Road network and other infrastructure (1:50,000 or larger)
• Underwater topography (1:50,000 or larger)
• Water drainage and water bodies (1:50,000 or larger)
• Tide limits
• Geology (1:100,000 or larger)
• Soil type (1:50,000 or larger)
• Land use/cover (1:50,000 or larger) as obtained from most recent land-use maps available
• Demography (associated with administrative boundaries)
• Resource harvesting activities (administrative area, type and quantity)
• Other relevant information in map form (water quality parameters, etc.)

3.1.2 Remote sensing imagery

Three satellite images will be provided for each pilot area. Two of them will correspond to SPOT-HRV data acquired any time between the launch of SPOT in 1986 and the present. These two SPOT images will be provided to each study team free of charge by the Government of France, which is funding the project. The third image may be from any of the higher-resolution sensors of SPOT, Landsat (TM) or IRS (LISS-II) depending on the availability of a suitable cloud-free image. This third image will be provided by the project.

Satellite imagery (already in digital format) and aerial photographs (which need to be digitized) will be included in the database in both original/raw format and processed through image analysis techniques (thematic maps obtained through classification, principal components, vegetation indices, etc.). All images (raw and processed) will have been previously geometrically rectified to a common geographic coordinate system. These include:

(a) SPOT XS bands 1, 2 and 3 of DATE 1 (preferably cloud-free image acquired between 1986 and 1989);

(b) SPOT XS bands 1, 2 and 3 of DATE 2 (preferably cloud-free image acquired between 1989 and 1993);

(c)SPOT XS, Landsat TM or IRS LISS-11 image of DATE 3 (preferably cloud-free image acquired between 1993 and present);

(d) Aerial photographs at 1:10,000-1:25,000 scale acquired after 1992.

Digital processing and/or visual interpretation of the satellite images should aim to delineate the following land-use/land-cover classes:

• Industry
• Agriculture
• Fish pond
• Inland forest
• Residence/built-up area
• Waste land
• Roads and other infrastructure
• Mangrove
• Underwater vegetation
• Other

and the following mangrove categories:

• Homogeneous mangrove forest
• Mixed dense mangrove forest
• Mixed open mangrove forest
• Other classification system (species association, etc.) if available

Graphic layers resulting from the thematic interpretation of the satellite images will include at least the following:

• Land cover DATE 1
• Land cover DATE 2
• Land cover DATE 3

3.1.3 Point data

Some useful information may be available from data collection platforms or measurement stations located in and around the coastal zone/mangrove area. When useful, these can be included in the database as point files which may be used to generate maps through various interpolation algorithms. These may include:

• Water temperature
• Salinity
• pH
• Concentration of suspended solids
• Other water quality parameters.

3.2 Database files and structure

The recommended database file structures and field descriptions are described in the following paragraphs.

3.2.1 Graphic database

The graphic database should be constructed from input maps at a scale of 1:50,000 for the pilot area and, if possible, at the scale of 1:25,000, for the sub-area where mangroves are found.

The graphic layers such as administrative boundaries, soil type, land-use type, mangrove category, and others should be identified with the same code number that they have in the attribute database, described in the following section.

3.2.2 Attribute database

The attribute database constructed for each of the four pilot areas will consist of four files, i.e. XXSBPHID relating to physical data, XXSBPOEC relating to socio-economic factors, XXSBROWA relating to infrastructure and waterways, and XXSBMANG relating specifically to mangroves.

The XX characters correspond to country codes:

• CN for China
• PH for the Philippines
• TH for Thailand
• VN for Viet Nam

The four files can be linked through Location-ID, which is unique to each pilot area. The identity consists of nine characters (XXYYYYZZZ):

• XX for country code (CN, PH, TH or VN)
• YYY for pilot area code
• ZZZ for land use and mangrove category code

The code number must be the same as the number of the graphic feature code

The XXSBPHID file will contain a collection of records of physical data in the pilot area. Its proposed structure is detailed below.

The XXSBPOEC file will contain a collection of records of socio-economic data over the pilot area. Its proposed structure is detailed below.

The XXSBROWA file will contain records of road and water data in the pilot area. Its proposed structure is detailed below.

The XXSBMANG file is designed specially for mangrove ecology and management. Its proposed structure is detailed below.

3.3 Data exchange formats

Part of the methodology involves the consideration of data exchange formats. The use of a common format or "standard" will facilitate data exchange and integration and will increase the value of the data through improved meaningfulness.

Arc/Info, the GIS software common to all four designated agencies, is also common to the largest number of user agencies in the Asia-Pacific region and has input/output tools which are very effective for transferring data between like systems. Arc/Info Export is therefore an easy solution for the exchange of data within this project and for the construction of the report. Arc Export is a standard which is produced by all versions of Arc/Info software running on all platforms.

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4. Conclusions and recommendations

Management of the coastal zone environment and, in particular, mangroves is a big concern in all four countries participating in this project. The rapid degradation of this resource over the past 25 to 40 years in each of these countries has left but a small fraction of the coastline that used to be sheltered by mangroves. Coastal zone environment management is a priority and several projects making use of remote sensing and GIS technologies have already been carried out by a number of national agencies, including the four agencies designated for this project.

The interest of this particular project lies, for many, in the construction of a report that will integrate the results of all four countries. This package is seen as having the potential to be an extremely valuable tool for educational purposes as well as to promote the use of the technology to policy and decision makers who, in many cases, still know little about its vast potential for coastal zone environment management. The opportunity to work in cooperation with specialized agencies from other countries facing similar coastal zone management problems is also regarded as a very attractive component of the project.

4.1 Approach recommended for the project

As a TCDC project with limited funding availability, a very pragmatic approach was emphasized in discussions with the principal investigators during this initial assessment study. In all cases, pilot areas were determined, taking into account the existence of substantial amounts of data, preferably in digital form, and/or the current involvement of the designated agencies and/or collaborative agencies in related projects in the pilot area, and/or the high priority already assigned to the area.

Existing facilities are considered adequate in all four countries, whether inside the designated agencies or in cooperating institutions. High-power PCs and relevant software for digital image analysis and GIS functions are already available in all cases and can produce output that will be easily integratable in the report. Arc Info, the workstation or the PC version, is common to all four agencies. The PC versions of either PCI-EASI/PACE or ERDAS, two powerful image analysis software with similar capabilities, are also common to the four. In most cases, therefore, the requirements for equipment using the budget available for the project were rather small.

The greatest common requirement for assistance for this project related to the need to carry out field work in relatively far away areas. In three of the four countries, the pilot area is located between 300 and 600 km from the designated agency's headquarters. Transportation costs, daily allowances and logistics were seen as a burden for which it could be difficult to obtain in-house funding.

All principal investigators and research teams were enthusiastic about the project and confident that the human and material resources needed to fulfill the study objectives could be mobilized, especially if some seed were available from the project/ESCAP. GIS experts and/or experienced operators were part of the project team in each country, and the construction of digital geo-referenced databases using GIS had been performed on a number of previous occasions.

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