The Study on Coastal Zone Environment Management with Emphasis on Mangrove Ecosystem to Assist in Poverty Alleviation project involved four countries of the region, namely China, the Philippines, Thailand and Viet Nam. The project aims to facilitate the regular updating and appraisal 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 be useful for relevant agencies to carry out integrated coastal zone development planning.

A particular interest of the project lies in the construction of a report, comprising of a set of guidelines with pilot studies as case studies. The major aims of the report are to:

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

o the monitoring of changes in mangrove ecosystems;

o 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.

The report is seen as having the potential to be a valuable tool for educational purposes as well as to promote the awareness of policy and decision makers on the use and potential of remote sensing and GIS technology for coastal zone environment management.

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 national focal points of the Regional Space Applications Programme for Sustainable Development (RESAP) of ESCAP, and their research teams in the four countries. The initial study provided an overview of the status of mangroves in each country.

In China, the mangrove forest 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.

In the Philippines, mangroves were estimated to cover as much as 400,000-500,000 hectares in 1918, 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.

In Thailand, mangrove forests 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; and South Thailand - West Coast (six 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.

In Viet Nam, a 3,200-km-long coastline 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 1962, 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. The quantity, quality and composition of mangroves have changed dramatically due to the use of herbicides and napalm during the Viet Nam war, resulting 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.

The project also developed guidelines on the procedures/methods to be followed by the principal investigators in producing their results. The countries worked following this common core methodology. The results of the study in pilot areas in Thailand and Viet Nam are reproduced in this report for dissemination to relevant institutions/agencies of other countries of the region confronted with coastal zone/mangrove management and protection.

The Ao Sawi-Thung Kha pilot area in Thailand 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.

The Can Gio pilot area in Viet Nam is located in the periphery of Ho Chi Minh City. Can Gio extends over 680 km² and has a population of 58,000 inhabitants. Can Gio is one of the two protected mangrove areas in Ho Chi Minh City. 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 No. 51. 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 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 Ho Chi Minh City 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.

The activities undertaken by ESCAP under the Regional Space Applications Programme for Sustainable Development and leading to the preparation of this report have been undertaken with financial assistance of the Government of France. The contribution is greatly acknowledged.