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The Mae Chan River, a tributary of the Upper Kwae Yai, which would be flooded by the Nam Choan's reservoir.

Thailand's Nam Choan Dam:

A Disaster in the Making by Belinda Stewart Cox

The Electricity Generating Authority of Thailand (EGAT) is currently canvassing for permission to build a huge hydro-electric dam in Thailand's western province, Kanchanaburi. The dam, the Nam Choan, would be the fourth large hydro-electric dam to be built in the province, all of them impounding the River Kwai of bridge fame. The Nam Choan Dam would harness the upper reaches of the river and would inflict irreparable damage on the Thung Yai Wildlife Sanctuary—the single most important conservation area in the whole of Thailand, Indo-

China and mainland South-east Asia.

A quick glance at any road map of Thailand wil l reveal that the far western region has fewer roads, fewer urban or rural settlements and fewer people than any other part of the country. That being so, i t wil l be no surprise to learn that the region is also guardian to Thailand's largest and finest conservation area, the Thung Yai and Huai Kha Khaeng Wildlife Sanctuaries.

These two sanctuaries form a contiguous block of almost 6,000 square kilometres (km2)—twice as large as any other conservation area i n Thailand, four and half times as large as any other legally protected area i n Indo-China, and almost 30 per cent larger than the rainforest reserve of Taman Negara i n Peninsula Malaysia, the closest rival i n size though not i n forest type 12 . Thus by virtu e of thei r size, these tw o sanctuaries can be regarded as the single most important conservation area i n Thailand, i n Indo-China and i n mainland South-east Asia.

Size is not their only distinction however. The two sanctuaries are also important by virtu e of their vegetation types and the number of endemic tree species occurring there3. The largest proportion of forest cover is mixed deciduous forest (also known as tropical

Belinda Stewart Cox, a graduate of Oxford University, has been studying the behaviour and ecology of the Green peafowl in Thailand's Huai Kha Khaeng Wildlife Sanctuary. She has recently joined a team of researchers from Kasetsart and Mahidol Universities to undertake a basic survey of bird species occurring in the Mae Chan valley of Thung Yai Wildlife Sanctuary. 212

monsoon forest), wit h large areas of dry deciduous dipterocarp forest and dry evergreen forest (also known as tropical semi-evergreen forest)45 . Dry tropical forest is now rarer than true tropical rainforest67. Large tracts of relatively undisturbed dry tropical forest are rarer still 8 . Therefore, the singular importance of Thung Yai and Huai Kha Khaeng Wildlife Sanctuaries lies not simply i n their being the largest conservation area i n mainland South-east Asia, but i n their being the largest single tract of protected dry tropical forest i n mainland South-east Asia9. That invests them wit h global as well as regional significance.

Rarity is one thing , diversity another. Wit h an altitudinal range from 250 metres above sea level to 1,811 metres, Thung Yai and Huai Kha Khaeng Wildlife Sanctuaries provide the topographic conditions for great floral diversity. Not surprisingly, that diversity is there. Withi n thei r boundaries, these sanctuaries support seven vegetation types; the three dominant forest types already mentioned (mixed deciduous forest, dr y deciduous dipterocarp forest and dr y evergreen forest) together wit h tropical lower montane rainforest on the heights, gallery evergreen forest along enclosed watercourses, patches of bamboo forest and the savannah or grassland forest from which Thung Yai takes its name (Thung Yai means "Bi g Field") 1011 . The presence of so many undisturbed habitat types i n one region is very rare indeed.