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Likely impact of destruction of rocky rapids and bedrock along the Mekong River in Thailand upon birds.

Philip Round

Conservation Committee

Bird Conservation Society of Thailand

July 2002


Large riverine ecosystems support an important array of species which are scarce and absent from other wetlands.  The Mekong River is well known in supporting the Mekong Giant Catfish Pangasianodon gigas, the Giant Carp Catlocarpio siamensis and in sustaining important fisheries for a great range of smaller species.

The importance of the Mekong River for birds and other wildlife is much less known, but is beginning to be addressed.  Rivers present particular conservation problems since, as linear habitats, they are not easily amenable to designation as protected areas. Management of riverine ecosystems is complicated by the fact that rivers are usually settled along their banks, and subject to a great array of human uses.  In addition, human activities upstream can affect large areas downstream, remote from the original disturbed areas.  In particular, gross alterations to hydrography and water quality, rate of flow, etc. as will be caused by major river works such as dams and dredging of sand-bars or destruction of rocky outcrops. 

This paper considers the likely effects upon the bird community of the Mekong River of blasting and river dredging, aimed at increasing the draft of boats which will ply their trade between China, Thailand, Laos and points downstream.

The Thai Government apparently signed an agreement for significant blasting of riverine rapids along the Mekong to take place during January 2002.  This agreement was signed without consulting any of the local communities who live along the river, and so far as known, no environmental impact assessment (EIA) was carried out.  When BCST representative approached a member of the Biological Resources Section, Natural Resources and Environmental Management and Coordination Division, Office of Environmental Policy and Planning to express our concern about these activities, we were informed that OEPP was not involved in assessing impacts from these activities as OEPP was not a “focal agency” for the Mekong River.  As usual, therefore, there is a deafening silence and apparent lack of concern from those government agencies whose responsibilities at least nominally cover environmental matters in general, and wetland habitats in particular. 

The only section of the river bordering Thailand which will be directly affected by the blasting is that upstream of Chiang Saen, where the river enters Thai territory, downstream to Wiang Khen district, where the river enters Laos again (approx 100 km).  However, a very long stretch of river in Luang Namtha and Bokeo Province, Laos (450 km) will be dynamited or dredged so the overall impact from work conducted in Laos may be greater than that in Thailand.  Subsequently in this paper, this is referred to as the “Upper Lao Mekong” following Duckworth et al. (in press) who surveyed birds along this section in 2000.  However, the comments made in this assessment for Thailand will broadly apply in Laos, where the same range of species and habitats will be affected. 

Duckworth et al.(1999, in press) have found that many of the most threatened birds in Laos, including species which have disappeared, not having been recorded for decades, are associated with riverine ecosystems.

The Mekong is far from being a pristine river.  On the contrary, a high level of human use over many centuries has gradually eroded its biodiversity.  Some birds, such as Indian Skimmer Rynchops albicollis have long gone: the last known records from the Lao-Thai Mekong seem to have been around 1930 (Duckworth et al., 1999). Nonetheless, in comparison with its surroundings (mainly arable farmland on the banks), it is still very rich in birds, and continues to support many species which are scarce or absent elsewhere.

Notes on threatened species

Some important and threatened bird species still found on the Mekong River are listed below.  National threat levels in Thailand follow Round (2000) and those for Laos follow Duckworth et al., 1999).  Globally threatened and near-threatened species are those listed by BirdLife International (2001). 


Blyth's Kingfisher  Alcedo hercules (Status: Thailand, Critical. Laos, Potentially at Risk. Global, Near-threatened)

In Thailand, this species is only known from a single specimen collected at Ban Phaeo, downstream of Chiang Saen, probably on a small tributary of the Mekong, in 1972 (Round, in prep.).  It would be unlikely to be directly affected by developments on the mainstream Mekong, but more vulnerable to deforestation and siltation along the tributarty streams on which it occurs.


Crested Kingfisher  Megaceryle lugubris (Status: Thailand, Vulnerable. Lao, Not at Risk)

This species is scarce and mostly on fast-flowing forest rivers with steep banks.  It was recorded at Chiang Saen by king (1966) and seen here again.  It may well be present, and undetected, along the section of river downstream from Chiang saen to Chiang Khong and would be vulnerable to large scale disturbance caused by blasting of rapids


Great Thick-knee Esacus recurvirostris  (Status: Thailand, Critical; Laos, At Risk)

Great Thick-knee is scarce and probably overlooked resident.  The only records of apparently breeding birds in Thailand or Laos in recent decades have come from the Mekong River, where it has been recorded on sandbars upstream of Chiang Saen, between Chiang Saen and Chiang Khong (the latter site as recently as December 2001; BCST Bulletin), near Pakchom (Loei province; more or less opposite Sangthong, where recorded in Laos; BCST Bulletin; Duckworth et al, in press) and at Khemmarat (Amnat Charoen Province) and along the Mekong in the far south of Laos (Duckwoth et al., 1999).  It occurs in association with sandbars and also areas of exposed bedrock with bushes and scrubby growth.  The small populations remaining would therefore be directly affected by blasting or bedrock or dredging of sandbars to deepen river channels, which would destroy their habitat.


Long-billed Plover  Charadrius placidus  (Status:  Thailand, Near-threatened. Laos, Little known)

This very scarce winter visitor was recorded along the Mekong between Chiang Saen and Chiang Khong during winter 2001-2002 (BCST Bulletin), and has also been recorded upstream of Chiang saen  It frequents sand and shingle bars and could be affected by planned developments.  However, since the Thai wintering population is small this is unlikely to have a major global impact.


River Lapwing Vanellus duvaucelii(Status: Thailand, endangered.  Laos, At Risk)

Found in small numbers throughout all sections of the Thai-Lao Mekong. Duckworth et al. (in press) recorded a total of 130 on the upper Lao Mekong, but River Lapwing is already scarce, and much less numerous on those sections of the river in Thailand, due mainly to direct and indirect human disturbance of its riverine sandbar and shingle bar nesting habitat, and collection of eggs and young as food by fishermen.  Found upstream and downstream of Chiang Saen, and between the latter and Chiang Khong (up to 11, December 2001: BCST Bulletin) it would be adversely affected by additional disturbance caused by blasting of rocks and rapids.


Grey-headed Lapwing  Vanellus cinereus (Status: Thailand, Near-threatened. Laos, Potentially at Risk)

A few tens of birds winter on sandbars downstream of Chiang Saen and might be displaced by blasting activities.  However, since these species also winters widely on rice paddies, grazing marshes, this is unlikely to have major impact on the Thai wintering population as a whole.

Duckworth et al. (in press) considered the upper Lao Mekong to be an important wintering area for this species, which would be very badly impacted by blasting.


Black-bellied Tern  Sterna acuticauda  ( Status: Thailand, Critical.  Laos, At Risk Global, Near-threatened).

There is only one recent record of this species on the Thai-Lao Mekong, from Chiang Saen, in 1996 (BCST Bulletin; Thewlis et al., 1998). It formerly nested on riverine sandbanks, but is probably now close to being extirpated on the Mekong, and is therefore of critical conservation concern.  Any additional disturbance, such as alterations to riverine hydrology and perhaps also food supply caused by blasting could hasten the extinction of this species


River Tern  Sterna aurantia ( Status: Thailand  Critical. Laos, At Risk)

This species is already very scarce due to human disturbance of the sandbanks on which it nests.  There are recent records along the Mekong in Thailand from Chiang Saen, Vientiane) and from near Khemmaraj (BCST Bulletin; Duckwoth et al, 1999, in press).  Duckworth et al. did not record any on those sections of the upper Lao Mekong in Bokeo and Luang Namtha, reflecting the present extreme scarcity of this species in areas where formerly present or reasonably abundant. Most recent records from the Mekong are in S Laos, in the vicinity of Khone Falls (Duckworth et al., 1999).

Any additional disturbance, such as alterations to riverine hydrology and perhaps also food supply caused by blasting could prevent any possibility of recovery in numbers hasten the extinction of this species.


Great Cormorant Phalacrocorax carbo  (Status: Thailand, Critical. Laos, At Risk)

A single bird was present on sandbars upstream of Chiang Saen in early 2000 (BCST Bulletin, Duckworth et al., in press). This species is more threatened throughout SE Asia than its status elsewhere might suggest. It was once locally numerous, but populations everywhere have collapsed, possibly due to a combination of factors.  Along with other large waterbirds, both resident and migrant, it would be at risk from loss of habitat due to dredging or removal of sandbars, and possibly also reduction in its food supply (mainly fish).


Black Stork Ciconia nigra (Status: Thailand, endangered. Laos, At Risk)

This species is an occasional, and probably declining winter visitor to sandbars on the upper and middle stretches of the Mekong River, resting or loafing, and perhaps feeding on sandbars.  One was seen upstream of Chiang Saen in December 1983 (Duckworth et al., 1999) and three more close to the Mekong River at Nong Bong Kai in October 2001 (BCST Bulletin). As a large bird, there are few areas other than rivers where it can escape direct human persecution


Jerdon's Buschchat Saxicola jerdoni (Status: Thailand, Endangered. Lao, Not at Risk)

The largest population of this species known is on the middle Mekong around and upstream of Pakchom District in Thailand (opposite Sangthong District, Laos) estimated by Duckworth (1997) at 100 + pairs.  Birds occur in association with Homonoia riparia bushes (Duckworth et al., in press) on riverine sand and single bars and exposed bedrock in “braided channel” habitat. Jerdon's Bushchat apparently does not extend anywhere further downstream along the Mekong.

Jerdon's Bushchat is present around Chiang Saen in very small numbers. However, the area of scrubby sand and shingle bars and exposed bedrock from Chiang Saen downstream to Chiang Khong, which has never been properly surveyed for this species, almost certainly supports a sizeable population of Jerdon's Buschchats, as the habitat appears closely similar to that at Pakchom. It is likely, therefore, that a sizeable population occurs of at least national and probably regional conservation importance and would be directly damaged by blasting or destruction of riverine bedrock.  Moreover, the population at Pakchom is already possibly at risk due to dredging of sand for construction.


Plain Martin  Riparia paludicola (Status:Thailand: Endangered. Laos, At Risk)

Plain Martin is very scarce along the Mekong River, where it nests in vertical earth banks.  One such colony at the confluence of the Nam Ruak and the mainstream Mekong, upstream of Chiang Saen, has already been lost due to the banks being concreted and graded.  Elsewhere only a few individuals have been recently reported at Thai Mekong sites such as Pakchom.  However, Duckworth et al. (in press) recorded numbers in the low hundreds on the Upper Lao Mekong, the pricincipal area that might be affected by blasting and dredging


Wire-tailed Swallow  Hirundo smithii (Status:Thailand: near-threatened. Laos, Potentially at Risk)

This swallow is mainly associated with river rapids.  Numbers at Pak Mun are believed to have declined due to demolition and submersion of the rapids there resulting from construction of the Pak Mun dam.  Though widely distributed along rocky sections of the Mekong, numbers are small, having presumably declined since “thousands” were reported ca. 50 years ago (Duckworth et al, 1999).  Although this species disperses widely over cultivated land, nesting under (e.g., roadside culverts, rivers constitute its core habitat, and dynamiting of bedrock would directly affect numbers.

Other bird species

In addition to the above threatened species, there are a great number of other, primarily wetland birds, which occur along the Mekong River in significant numbers and are scarce elsewhere.


Spot-billed Duck  Anas poecilorhyncha

This bird is widely distributed in small numbers on many sections of the Mekong, where it is thought probably to be a breeder.  Apparent pairs are mostly in areas of braided stream channels, interspersed with bedrock, single bars, islands and scrub since these provide terrain in which human disturbance is minimized. 

Significant wintering concentrations are usually present on sandbars at Chiang Saen (largest flock 64 birds, February 2002; BCST Bulletin) and move between the river and nearby Nong Bong Kai.


Little Ringed Plover  Charadrius dubius

Small numbers nest widely on sandbars on the Mekong, including around Chiang Saen and would be directly affected by disturbance through dredging of removal of this habitat.


Small Pratincole  Glareola lactea

This species nests exclusively on riverine sandbars, and is the most numerous and abundant riverine nesting bird remaining.  Though widespread on the Thai-Lao Mekong, the largest single concentrations known are around Chiang Saen, with at least 840 upstream of the town in early 2000 (Duckworth et al., in press) and a further 1,600 between Chiang Saen and Chiang Khong in February 2002 (BCST Bulletin).  Numbers elsewhere are apparently much less.  This species would be directly affected by dredging of sandbars and blasting of bedrock, and numbers possibly much reduced.


Miscellaneous waterfowl

The Thai sections of the Mekong River support large numbers of wintering waterfowl of a great range of species.  In addition to those already listed these include herons (especially นกกระสานวล  Grey Heron Ardea cinerea); ducks (เป็ดหางแหลม  Northern Pintail Anas acuta; occasional เป็ดพม่า Ruddy Sheduck Tadorna ferruginea); นกชายเลนอื่นๆ  waders (up to 350 นกทะเลขาแดงลายจุด Spotted Redshanks Tringa erythropus recorded wintering at Chiang Saen; and a great range of other wader species including นกหัวโตขาดำ  Kentish Plovers Charadrius alexandrinus, นกสติ๊นท์อกเทา  Temminck's Stint Calidris temminckii, and occasionally a few นกชายเลนท้องดำ  Dunlin Calidris alpina, a nationally scarce species in Thailand).  The only records of three species of geese, ห่านหัวลาย  Bar-headed Goose Anser indicus, ห่านเทาปากสีชมพู  Greylag Goose A. anser and the globally threatened ห่านคอขาว Swan Goose A. cygnoides in Thailand have come from this area.

Important Bird Areas

At least five sites along the Mekong River, where it forms the border with Thailand and with Laos, are considered to be Important Bird Areas (IBAs) by BCST-BirdLife Thailand and BirdLife International. These are areas which are thought to be especially good examples of Indo-Gangetic plains riverine habitat and which support nationally or globally important concentrations of species, and which are therefore worthy of conservation (Table 1). Two of these (upstream of Chiang Saen to the Golden Triangle, and downstream of Chiang Saen to Chiang Khong) would be directly affected by blasting and dredging of riverine rapids.  The three others could well suffer indirectly from downstream effects

Key Bird habitats

Some important riverine habitats for birds are listed below.

1)  Open sand-bars: these support nesting species (นกนางนวลแกลบท้องดำ Sterna acuticauda,. นกนางนวลแกลบแม่น้ำ S. aurantia, นกนางนวลแกลบเล็ก S. albifrons, นกกระแตหัวเทา Vanellus duvaucelii, นกหัวโตเล็กขาเหลือง Charadrius dubius, นกแอ่นทุ่งเล็ก Glareola lactea) and a great range of wintering species: many นกเป็ดน้ำ ducks, นกชายเลน waders, เหล่านกยางและกระสา herons, cormorants, นกเด้าลม wagtails, นกเด้าดิน pipits, etc., including species nationally at risk such as นกกระสานวล Grey Heron and นกกระแตหัวเทา Grey-headed Lapwing.  Large and significant sandbars occur upstream of Chiang Saen, at Sob Ruak are probably the single most important area of the upper Mekong for numbers นกน้ำอพยพในช่วงฤดูหนาว wintering waterfowl.

2) Beds of tall grasses on sandbars (usually associated with sandbars) support many small birds, including นกพง warblers, นกจาบปีกอ่อน roosting buntings, and nesting นกกระติ๊ดแดง Red Avadavats Amandava amandava.  A few นกยอดหญ้าหลังดำ Jerdon's Bushchats nest in such habitats, and the very scarce wintering chat นกคอทับทิมอกดำ White-tailed Rubythroat Luscinia pectoralis has also been recorded in similar reed or can-grass habitat from marshy areas around Chiang Saen.  Significant areas of this habitat occur all the way along the Thai section of the Mekong from the Golden Triangle downstream at least as far as Chiang Khong.

3) Exposed bedrock and so called braided channels, alternating with small sandy/shingly patches often occurs in association with Homonoia riparia scrub. 

This is probably the most diverse riverine habitat for birds, important for a range of species:  เป็ดเทา Anas poecilorhyncha (possibly breeds); นกกระแตผีใหญ่ Esacus recurvirostris (nationally endangered, but still breeds); นกนางนวลแกลบแม่น้ำ Sterna aurantia, นกนางแอ่นหางลวด Hirundo smithii and นกยอดหญ้าหลังดำ Saxicola jerdoni  (large, little appreciated populations still occur in this habitat) and both resident and migrant warblers, นกกินแมลงตาเหลือง Yellow-eyed Babbler Chrysomma sinense and นกกินแมลงกระหม่อมแดง Chestnut-capped Babbler Timalia pileata.

Extensive tracts of this habitat occur downstream of Chiang Saen, to Chiang Khong.  This seems to be the section of the Thai –Lao Mekong which would be badly damaged by blasting.

4) vertical earth banks

These constitute nesting habitat for colonies of นกนางแอ่นทรายสีน้ำตาล Plain Martins, and probably also นกจาบคาหัวเขียว Blue-tailed Bee-eater Merops philippinus.  Vertical earth banks of > 1 m height occur both along the main stream banks and on offshore islands.

Downstream affects

The downstream effects of blasting rocks on the upper Mekong are hard to predict, but could be very considerable through altered hydrology (flow rates, sedimentation, changes in sedimentation patterns) and could drastically affect the ecology or the river many hundreds of kilometres downstream of where the blasting is carried out.  This could worsen bankside erosion, and wash away sandbars and islands which are important for birds. 

Rocky and shingly reaches of the Mekong River, and some major tributaries in southern Laos and northern Cambodia support a newly discovered endemic bird species, นกเด้าลมแม่น้ำโขง the Mekong Wagtail Motacilla samveasnae (Duckworth et al., 2001).  The first two specimens of this were collected near Pak Mun, in Khong Chiam District, Ubon Ratchathani Province.  It is virtually certain that this species does not extend on to the upper Mekong, but nevertheless it might be vulnerable to changed river flow and siltation resulting from upstream blasting works.

Costs and benefits

As is usual with developments of this nature. no significant effort has been given to appraising the likely environmental costs, or the social and economic impacts on local people.

The precise impacts may be hard to judge, and will depend partly upon the scale of the work to be conducted.  However, since authorities have not released any information on this, NGOs and environmental and social bodies are justified in assuming a worst-case scenario.  The difficulty of judging precise environmental impacts should not be used as a justification for going ahead and seeing what happens.

The sole benefit of the proposed developments on the Mekong would be to improve transport of goods between China and Thailand.  The major beneficiary of this would be China, which seeks to expands its economic dominance over SE Asia. It is unlikely that reciprocal benefits will accrue to Thailand from trade, since Thailand is less able to compete in either volume of cost of agricultural produce (Thai labour costs are much higher).  In addition, any possible benefit to trade from the river would likely be overshadowed in a few years when the highway extending from North Thailand to Kunming (already under construction) is completed

The potential benefits, therefore are questionable, especially to those countries who will bear most of the environmental impact (Thailand and Laos).

The costs are likely to be very considerable.  They are likely to result in the disappearance or gross degradation of diverse riverine bird communities and ecosystems which are not found anywhere else in Thailand.  Already endangered species such as นกกระแตผีใหญ่ Esacus recurvirostris and นกนางนวลแกลบแม่น้ำ Sterna aurantia may go extinct, while the numbers of a great range of other species, including นกแอ่นทุ่งเล็ก Glareola lactea and นกยอดหญ้าหลังดำ Saxicola jerdoni will be greatly reduced. In addition, the value of the existing Ramsar site at Nong Bong Kai seems likely to be reduced.  At the present time, part of the richness of Nong Bong Kai is due to the presence of suitable loafing and feeding areas on the Mekong River, to which ducks and herons from the lake may commute.  Removal of riverine sandbars upstream of Chiang Saen may prevent such traffic between lake and river.

The effects on the Mekong river are likely to be considerable, through removal of feeding and or spawning areas for a range of fish species.  Changes in (e.g.) flow rates could lead to a cascade of changes that will greatly diminish the volume and richness of the present fishery.

Changes in hydrology may well also exacerbate problems of bankside erosion.  This will necessitate building expensive concrete embankments, at cost to the taxpayer.  These will destroy present bankside nesting habitat for hole-nesting species such as นกนางแอ่นทรายสีน้ำตาล Plain Martins and นกจาบคาหัวเขียว Blue-tailed Bee-eaters.

To summarise, therefore, while profits, if any, accrue to businessmen, the environmental and lifestyle costs will be borne by the many tens of thousands of lower income people who depend on their river for fisheries and other small scale uses.  In addition, the richness and diversity of Mekong river riparian community will be greatly diminished.


BirdLife International  2001.  Threatened birds of Asia: The BirdLife International Red Data Book.  Birdlife International, Cambridge, U.K.

Duckworth, J.W. 1997.  Observations on a population of Jerdon's Bushchats Saxicola jerdoni in the Mekong Channel.  Bull. Brit. Orn. Cl. 117: 210–220

Duckworth, J.W., Salter, R.E.,  and Khounboline, K. 1999.  Wildlife in Lao PDR: 1999 Status Report. IUCN- The World Conservation Union, Wildlife Conservation Society and Centre for Protected Areas and Watershed Management, Vientiane

Duckworth, J.W., Alstrom, P., Davidson, P., Evans, T.D., Poole, C.M., Tan Setha and Timmins, R.J. 2001.  A new species of wagtail from the lower Mekong basin.  Bull. Brit. Orn. Cl. 121(3): 152–182.

Duckworth, J. W., Davidson, P., Evans, T. D., Round, P. D. and Timmins, R. J. (in press)  Bird records from Laos, principally the upper Lao Mekong and Xiangkhouang Province, in 1998–2000.

Round, P.D.  2000 Field Check-List of Thai Birds.  Bird Conservation Society of Thailand, Bangkok.

Thewlis, R.M., Timmins, R.J., Evans, T.D. and Duckworth, J.W. 1998.  The conservation status of birds in Laos.  Bird Conservation International 8: (Supplement) 1–159.


Table 1. List of Mekong River Important Bird Areas (IBAs) in Thailand

Name of site Habitat Nationally and regionally Rare species Significance
1. Chiang Saen (Golden Triangle) Broad riverine sandbars Phalacrocorax carbo Ciconia nigra Vanellus duvaucelii, Esacus recurvirostris, Sterna aurantia, S. acuticauda, Saxicola jerdoni Major site for wintering waterfowls and nesting Vanellus duvaucelii and Glareola lactea
2. Chiang Saen- Chiang Khong Riverine sandbars and bedrock Vanellus duvaucelii, Esacus recurvirostris, Sterna aurantia, S. acuticauda, Saxicola jerdoni


Important area for wintering waterfowl; over 100 species of birds recorded; important nesting area for Glareola lactea (>1,000 breeding pairs)
3. Pakchom Riverine sandbars and bedrock Esacus recurvirostris, Saxicol jerdoni Largest known population of Saxicola jerdoni in Se Asia
4. Hat Sung-  Khemmeraj Rocky rapids/bedrock Esacus recurvirostris, Sterna autantia Regular site for Esacus recurvirostris
5. Pak Mun Rocky rapids and shingle bars Haliastur indus, Hirundo smithii, Motacilla samveasnae Only known Thai site where Motacilla samveasnae occurs


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