The IBA comprises the entire Cambodian stretch of the Sesan River and associated riverine vegetation, from its confluence with the Sekong River to the international border with Vietnam. The Sesan River is relatively wide, averaging c.150 m wide in the upper reaches and c. 300 m wide lower down. Most sections of the river are dominated by sand and gravel bars, apart from the lowest section, below Phum Khsach Thmei, which is much more rocky. In the upper reaches of the river, bars comprise mostly gravel, often with low shrub growth, while those in the lower reaches are almost entirely sand, with little or no shrub growth. The riverine vegetation is dominated by semi-evergreen and mixed deciduous forest, which grades into deciduous dipterocarp forest away from the river. The riverine vegetation is generally degraded throughout, mainly as a result of shifting cultivation.The IBA supports one of the best remaining examples of the riverine bird community that was once widespread along wide, lowland rivers in Indochina. This community includes River Lapwing Vanellus duvaucelii, Small Pratincole Glareola lactea, Great Thick-knee Esacus recurvirostris and River Tern Sterna aurantia, of which the IBA supports over 1% of the Asian biogeographic population of the former two. In addition, the IBA supports Mekong Wagtail Motacilla samveasnae, a recently described species, which is thought to be endemic to the Mekong River and its major tributaries. Furthermore, the IBA may be one of the last remaining sites in Indochina to support a breeding population of Black-bellied Tern Sterna acuticauda, although this is probably now limited to one or two pairs, and with changes in flow regime following the development of hydropower schemes upstream, on the verge of extinction.
Other regionally significant birds recorded: Grey Heron, Purple Heron, Woolly-necked Stork, Cotton Pygmy-goose, Brahminy Kite, Great Thick-knee (13 recorded in May-June 1998 by Timmins and Men Soriyun in prep.), River Tern (47 recorded by Timmins and Men Soriyun in prep. In May-June 1998), Green Imperial Pigeon, Alexandrine Parakeet, Pied Kingfisher (36 recorded by Timmins and Men Soriyun in prep. May-June 1998), Golden crested Myna, Great Slaty Woodpecker, Black Eagle.
Non-bird biodiversity: Timmins and Men Soriyun (in prep.) recorded Long tailed Macaque (Macaca fascicularis) Near- threatened, and Otter sp. Possible Smooth-Coated (Lutra perspicillata) Vulnerable. Baird (1997) reported Irrawaddy Dolphin (Orcaella brevirostris) (data deficient) to have much declined, documenting only a population of 2-5 animals near the confluence with the Sre Pok River. The following red listed fish species presumably occur: Probarbus jullieni, P. labeamajor, Pangasius sanitwongsei, and possibly Pangasianodon gigas. (Rainboth 1996).Long-tailed Macaque (Macaca fascicularis), ang Silvered Langur (Semnopithecus cristatus).Giant Asian Pond Turtle (Heosemys grandis), Siamese Crocodile (Crocodylus siamensis).
Pressure/threats to key biodiversity
Major threats to biodiversity at the IBA include hunting and, more importantly, egg collection and disturbance due to human activities on sandbars, which is likely to negatively affect the breeding success of sandbar-nesting birds. Another threat is posed by degradation and loss of riverine forest, due to cutting of trees and clearance of land for agriculture. A further major threat comes from the existing and planned development of hydropower schemes upstream in Vietnam. There is some evidence that the changes in flow regimes due to existing hydropower dams are already negatively affecting nesting riverine birds, by both sudden flash floods destroying nests and changes in the process nameof sedimentation leading to a reduction in the availability of nesting sites.
Conservation responses/actions for key biodiversity
Recommendations; Efforts must be made to protect sandbar-nesting bird species while they are breeding. Community agreements could be set up with individual villages so that the nest areas will not be disturbed. - Conservation of the Sesan River should be at the scale of the complete length of the river system as focusing on just a small stretch in isolation could have disastrous consequences. - New villages and agricultural development along the river should be discouraged and key stretches of riverine forest identified should be strictly protected from logging and shifting cultivation. - Research should be carried out focusing on the effects of the Sesan Dam HEP development on the bird communities, particularly the breeding success of sandbar-nesting species.
BirdLife International (2022) Important Bird Areas factsheet: Sesan River. Downloaded from
http://www.birdlife.org on 19/08/2022.