1.1 General

This project is directed in providing information about land cover at a regional scale for selected countries in the Asian region (e.g., Cambodia, Vietnam, Lao P.D.R., Myanmar, Bangladesh and Nepal). The investigation of the NOAA AVHRR satellite data is directed towards the detection and monitoring of ecologically important vegetation types at the national level. This similar activity also highlights the areas where there is a major change of land cover (i.e. "hot spots"), both in temporal and spatial aspects.

The use of remotely sensed data particularly the NOAA AVHRR data was considered a major tool for such purpose. On a much wider scale, this kind of information could also be useful for global research and modelling, macro-economic studies, and assessment of the earth's state of environment. The harmonization of land cover categories was adopted in the interpretation of satellite data for these countries towards a comprehensive regional resource assessment and information aggregation, an important decision input for the regional and national context.

Under this volume, the land cover of Cambodia and its related information have been presented while the overall rational behind this activity and its associated methodology appeared in Volume 1-A. It is envisioned that such results will serve as a valuable information for a more direct and appropriate formulation of policies and sensible resource management strategies.

1.2 Cambodia: Study Area

1.2.1 Location and Physical Characteristics

Cambodia occupies a compact territory covering 181,035 sq.km. in the southwestern corner of Indochina, bordered by Thailand to the west, Lao P.D.R. to the north, Vietnam to the east and Gulf of Thailand to the south. The central plain which is frequently flooded spreads along the Mekong River and Tonle Sap (Great) Lake. The rich sediment deposited during the Mekong's annual wet season flooding has made the agricultural lands highly fertile. In the south-west, much of the area between the Gulf of Thailand and the Tonle Sap is covered by a highland region formed by two distinct upland blocks, the Cardamom Mountains and the Elephant Mountains. About two-thirds of the total population lives in the central plain. Elevations exceed 1,500 m only in the Cardamom range in the southwest and in the Annamite range on the Lao P.D.R. and Vietnamese borders in the northeast.

Cambodia is part of the monsoon Asia and tropical climatic zones, with pronounced wet and dry seasons. The dry season is between November and April. Rain falls mainly in May-June and around September-October. The heaviest precipitation is recorded along the coast, where it averages between 2,000 and 3,800 mm/year. In the central plain, annual precipitation is between 1,000 and 1,400 mm/year.

1.2.2 Present Land Cover

Cambodia has the largest intact deciduous forests remaining in Southeast Asia. Deciduous monsoon forest, including dry dipterocarp and semi-evergreen dipterocarp forest, is found mainly in the north along the border with Thailand. Hill evergreen rainforest remains along the southern uplands and the Annamite chain in the east. Freshwater permanent and seasonal swamp forest are found in the area surrounding the Tonle Sap. The same vegetation formation, dominated by Melaleuca, is located in the Mekong delta on the southeast frontier adjacent to Vietnam. Only discontinuous bands of mangrove now remain around Veal Renh and Kompong Som bays, and in the north of Kas Kong, up to the border with Thailand (IUCN, 1991).

The 1991 Reconnaissance land use map of Cambodia indicates 68.8% of the country is forests and woodland while 20.9% is arable and permanent crop land. The forest areas are classified as closed forest, permanent swamp forest, mangrove forest, mosaic of evergreen or deciduous forest/secondary vegetal formation, mosaic of flooded forest/swampy vegetation/fallow land, secondary vegetal formation, pine forest, deciduous forest, thickets and scrub.

The most serious cause of deforestation has always been shifting cultivation and fire. Deforestation intensified during 1979-1992 which was a period of unsettled political situation in the country. The FAO (1991), as cited by Woodsworth (1991), reported that 85% of the calculated woodlands is used for shifting cultivation and is subject to widespread fires on an annual basis.