The IBA is located on the Nakai plateau, in central Lao P.D.R., and is partly included within Nakai-Nam Theun National Protected Area. The topography of the IBA is largely flat, at elevations between 500 to 600 m asl. The vegetation of the IBA is dominated by a mosaic of old-growth pine forest and semi-evergreen forest (Evans and Timmins 1998). The IBA is drained by the Nam Theun and its many tributaries, which support riverine dry evergreen forest (Thewlis et al. 1998). Pools and marshes are numerous in the centre of the IBA, although many have been the focus of human settlement and are degraded (Thewlis et al. 1998). The rivers within the IBA are important for the conservation of a number of species, including White-winged Duck Cairina scutulata, Blyth's Kingfisher Alcedo hercules, River Lapwing Vanellus duvaucelii and Lesser Fish Eagle Ichthyophaga humilis (Evans et al. 1997, Duckworth et al. 1998a, Evans and Timmins 1998). Of these, the population of White-winged Duck is the most significant, as it is one of the largest known populations of this globally endangered species in Lao P.D.R. (Evans et al. 1997, Thewlis et al. 1998). The IBA, together with contiguous forested lower mountain slopes, supports an important population of Brown Hornbill Anorrhinus tickelli (Evans and Timmins 1998), although the forests of the IBA do not, by themselves, have an exceptional bird fauna (R. J. Timmins in litt. 2002). In addition, the IBA is the only site in Lao P.D.R. from where there are recent confirmed records of Wood Snipe Gallinago nemoricola and Grey-sided Thrush Turdus feae, although, at least in the case of the latter species, which is known to be irregular in non-breeding occurrence, the IBA may not be of great importance for their conservation. Finally, the IBA supports part of one of the two largest populations of Asian Elephant Elephas maximus remaining in Lao P.D.R. (Duckworth et al. 1999).
The IBA supports population of at least 10 Key sepcies of bird including very rare species in Laos such as White-winged Duck, Wood Snipe and Grey-sided Thrush. Inspite of this so importance, the site was set aside for The Nam Theun 2 Hydro-electric Project and the three species of birds as well as other IBA Key species in the area are epected to have been affected severely.
Non-bird biodiversity: Timmins and Evan (1996) recorded five species of other important fauna: Sunda Pangolin M. javanica, Dhole C. alpinus, Asiatic Black Bear U. thibetanus, Sun Bear U. malayanus and Oriental Small-clwed Otter A. cinerea.Timmins and Evans (1996) recorded three species of primate: Slow Loris Nycticebus coucang, Pig-tailed Macaque Macaca nemestrina and a gibbon species Hylobates sp.Timmins and Evans (1996) recorded three species of elephant and ungulate: Asian Elephant Elephas maximus, Gaur Bos gaurus and Banteng B. javanicus.
Pressure/threats to key biodiversity
The biggest threat to biodiversity at the IBA is the planned Nam Theun 2 hydropower scheme, which is scheduled to inundate a third or more of the plateau, including all larger and most smaller streams (Thewlis et al. 1998). This would have significant impacts on a number of species, including White-winged Duck and River Lapwing (Evans and Timmins 1998), all of which are dependent on riverine habitats. However, even if the hydropower scheme goes ahead, the river system within the IBA may remain one of the most important in Lao P.D.R., particularly for fish eagles and otters (R. J. Timmins in litt. 2002).