Figure 1 Schematic flowchart of the methodology

Analysis Of Gis
Analysis of GIS was performed under vector GIS of PC Arc/Info. Four main outputs were derived based on the complied and extracted geographic databases as follows:

1. land use and land cover in 1973, 1987, 1993 and 1998;
2. forest distribution in 1993, 1987, 1993 and 1998;
3. change in land use and land cover between 1987-1993 and 1993-1998;

The basic techniques employed in the GIS analysis were overlay operation where two layers were input to extract a new layer. For example, for change in land use and land cover change 1987 and 1993, "the two inputs layers were land use and land cover in 1987 and 1993". The new layer was " change of land use and land cover during 1987 and 1993".

Results
The major results are the compilation of relevant thematic databases, assessment of forest land use and forest distribution in 1973, 1987, 1993 and 1998, as well as change in land use and land cover between 1987-1993 and 1993-1998 and development of a proposed forest land use plan.

Assessment of land use/land cover The land use and land cover categories in 1987, 1993 and 1998 were extracted by visual interpretation of satellite images at a scale of 1:50,000. Categories consist of (1) agriculture area; (2) built-up area; (3) forest area; (4) water bodies; (5) wasteland; (6) wetland and (7) shrimp farms. For land use and land cover categories in 1973 directly interpreted from a topographic map at a scale of 1: 50,000 are composed of (1) agriculture area (2) built-up area (3) forest area (4) water bodies (5) wasteland and (6) wetland. The components of land use and land cover in 1973, 1987, 1993 and 1998 are summarized and compared as shown in Table 1.



Forest Distribution
Based on visual interpretation of satellite imageries at the scale 1:50,000, forest area was further classified into three classes according to the their signature appearance on the image and their characteristics. Major forest types are mangrove, evergreen and freshwater swamp forest. The distributions of forest in 1973, 1987, 1993, 1998 . In addition, mangrove forests are further classified based on crown cover into three classes, namely mangrove with more than 75 % coverage, mangrove with 50-75 % coverage and mangrove with less than 50 % coverage.

The component of forest distribution in 1987, 1993 and 1998 are summarized and compared as shown in Table 2. The characteristics and change of forest classes are described as follows:

• Mangrove with > 75 % coverage. These mangrove forests mostly consist of Rhizophora apiculata and R. mucronata situated along the river channels and behind the pioneer species zone(Figure 2). The extent of mangrove forest with density of more than 75 percent increased during 1987 to 1998 and covered an area of 290, 488 and 519 ha, in 1987, 1993 and 1989, respectively. The main cause of increasing area is natural succession and reforestation.
  
  
  Figure 2 Pioneer species profile
• Mangrove with 50-75 % coverage. These mangrove forests mostly consist of pioneer species, Avicennia alba and A. officinalis situated on the outer fringe facing the sea (Figure 3). The extent of mangrove with density more between 50 to 75 percent decreased slightly during 1987 to 1998. These areas covered an area of 1,267, 1,140 and 1,091 ha, in 1987, 1993 and 1989, respectively. The main cause of decrease is natural succession by Rhizophora spp. and die back by sand deposit.
  
  
  Figure 3 Rhizophora species profile
• Mangrove with < 50 % coverage. These mangrove forests mostly consist of mixed species including Bruguiera cylindrica, Ceriops tagal, Excoecaria agallocha, Ficus sp., Heritiera littoralis, Hibiscus tiliaceus, Intsia bijuga, Xylocarpus granatum, and X. moluccensis situated behind the Rhizophora species zone (Figure 4). The extent of mangrove with density of less than 50 percent decreased from 1987 to 1998, covering an area of 3,846, 1,900 and 1,696 ha, in 1987, 1993 and 1989, respectively. The main cause the decrease is the expansion of shrimp farms. Figure 3 Mixed species profile
  
  
  
• Evergreen forest. Evergreen forests situated on the mountainous area decreased from 1987 to 1998. These forests covered an area of 2,691, 2,583 and 2,565 ha, in 1987, 1993 and 1989, respectively. The main cause of the decrease is the expansion of agriculture areas.
• Freshwater swamp forest. This forest mostly consists of Melaleuca leucadendra situated on flat areas behind the mangrove forest. The extent of swamp forest increased during 1987 to 1993 and decreased between 1993 and 1998. This forest type covered an area of 517, 551 and 527 ha, in 1987, 1993 and 1989, respectively.