How Dams Damned Thailand’s Birds

The Chiew Larn Dam Reservoir, constructed three decades ago, has had a negative impact on bird diversity, according to researchers in Thailand.

AsianScientist (Dec. 18, 2018) – A research group in Thailand reports that a dam built in Thailand 31 years ago has caused the local bird population to collapse. They published their finding in the journal Global Ecology and Conservation.

International entities, such as the World Bank, promote ‘good practice’ for reducing the impacts of hydropower on ecological systems. However, it can be a challenge to monitor biodiversity loss when dams are constructed.

In the present study, a team of scientists led by Dr. Gregory Irving of King Mongkut’s University of Technology, Thailand, studied how biodiversity around the Chiew Larn Dam Reservoir changed over time. They found that 24 square miles (61 square kilometers) of dry forest now surrounds the reservoir. The 63 square-mile (165 square kilometer) Chiew Larn Dam Reservoir inundated southern Thailand’s largest remaining tract of moist lowland rainforest—a unique habitat that was rich in biodiversity.

The researchers report that the area surrounding the reservoir is now permanently degraded due to deforestation and fire caused by humans. Hence, forest-dependent birds have largely vanished, as the once-contiguous rainforest has been replaced by isolated habitat patches overgrown with bamboo and vines.

Some native species are virtually missing from the area, including the rail babbler (Eupetes macrocerus), Malay peacock-pheasant (Polyplectron malaccense), straw-headed bulbul (Pycnonotus zeylonicus), Storm’s stork (Ciconia stormii) and the great slaty woodpecker (Mulleripicus pulverulentus)

More than half the birds recorded by the research team now consist of just a handful of wide-ranging and disturbance-tolerant species, including the pin-striped tit babbler (Mixornis gularis) and dark-necked tailorbird (Orthotomus atrogularis). Bamboo-loving species such as the bamboo bush-warbler (Abroscopus superciliaris), Indochinese blue-flycatcher (Cyornis sumatrensis), bamboo woodpecker (Gecinulus viridis) and white-browed piculet (Sasia ochracea) are also among the species that remain in the vicinity of the dam.

The authors noted that the results should serve as a cautionary tale as new hydroelectric projects are aggressively pursued in Asia. Without considering the potential for serious mainland edge effects and associated human disturbance of habitat, planners will underestimate the potential impact of hydropower development on bird biodiversity.

“Planning processes related to hydroelectricity development need to be undertaken based on a realistic understanding of the negative impacts that any proposed project would have on biodiversity, including irreplaceable loss of lowlands and degradation of mainland habitat induced by edge effects,” said Irving.

The article can be found at: Irving et al. (2018) Collapse of a Tropical Forest Bird Assemblage Surrounding a Hydroelectric Reservoir.


Source: Wildlife Conservation Society; Photo: Wich’yanan Limparungpatthanakij.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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