Rail babbler perched on a tree stump in a flooded forest, symbolizing habitat loss due to dam construction.

Thailand's Dams: A Looming Threat to Forest Bird Biodiversity?

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Theo Raines in Climate & Environment October 2026 • 4 min read.

"Study reveals the impact of dam construction on bird populations in Thailand's lowland forests, highlighting the urgent need for sustainable development practices."


Southeast Asia's rich biodiversity is increasingly threatened by rapid development, and dam construction stands out as a particularly disruptive force. While dams provide essential resources like water and electricity, their ecological impact can be severe and far-reaching.

A recent study published in Global Ecology and Conservation sheds light on the impact of dam construction on forest bird communities in Thailand. The research focuses on the Khlong Phrasaeng River in southern Thailand, where a dam built in 1986 has dramatically altered the landscape.

This article explores the findings of this crucial study, revealing how dam construction transforms ecosystems, displaces unique bird species, and underscores the urgent need for sustainable development practices in Asia and beyond. We'll examine the specific impact on bird populations, the broader implications for biodiversity, and potential strategies for mitigating these environmental consequences.

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Dam-Driven Changes to Bird Breeding

A 2018 study by an international team of conservation scientists reported that a dam built in Thailand 31 years earlier had caused the local bird population to collapse. Research published in 2022 examined water-level changes controlled by upstream dams and their effects on breeding success of sandbar-nesting birds in Bueng Kan Province, Thailand. The study describes dam-related water fluctuation as a threat to downstream biodiversity, including these birds.

Evidence of a Local Bird Decline

A study of a hydroelectric dam built in Thailand in the 1980s found that construction devastated the area's wild birds, leaving only a few of the many species that had once inhabited it. The report presents a documented local decline, but the supplied source does not describe a standard assessment method or compare methods and their limitations.

The Khlong Phrasaeng Dam: A Case Study in Ecological Disruption

Rail babbler perched on a tree stump in a flooded forest, symbolizing habitat loss due to dam construction.

Thirty years after the Khlong Phrasaeng Dam's construction, the surrounding environment has undergone a significant transformation. The damming of the river flooded 165 square kilometers of forest, creating approximately 100 islands within the reservoir. This dramatic change in landscape has had a cascading effect on the region's flora and fauna.

Researchers, led by Gregory Irving at King Mongkut's University of Technology Thonburi, investigated the dam's impact on bird communities. Their study compared bird species on land around the reservoir with those on 23 of the reservoir's islands. The findings revealed a concerning trend: the reservoir is now surrounded by at least 61 square kilometers of degraded habitat.

  • Habitat Loss: The flooding of forests directly eliminates habitat for forest-dependent bird species.
  • Species Displacement: Many specialized bird species are unable to adapt to the altered environment, leading to their displacement or local extinction.
  • Increased Competition: Common, adaptable species thrive in the degraded habitat, often outcompeting native birds.
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Research on Dam and Biodiversity Impacts

A 2024 review in Nature Reviews reports that more than 60% of rivers longer than 500 km are already fragmented, while thousands of dams are proposed on rivers in biodiversity hotspots. A separate source says a recent study published in Global Ecology and Conservation examines dam construction's impact on forest bird communities in Thailand, but the supplied snippet gives no study findings or figures. Research on large-scale hydropower development in tropical countries also highlights land-use change and biodiversity impacts, with Malaysia identified as a megadiverse example.

A Broad Review and Regional Knowledge Gaps

A 2019 review notes that many studies have examined dam construction's effects on biodiversity, while a review bringing that evidence together had been missing. Reporting from 2021 describes threats to otters, fish and birds along Thailand's Ing and Ruak rivers from hydropower dams on the Mekong. That report also says understanding of the dams' true ecological impacts on these tributaries remains lacking.

The study revealed that just nine common bird species accounted for half of all birds recorded in the degraded areas. More alarmingly, over a quarter of the bird species found in untouched habitat upstream of the reservoir have disappeared from the area since the dam's construction. The rail babbler (Eupetes macrocerus), once seen in the area, is a prime example; the last individual was rescued in the late 1980s as the reservoir filled.

The Future of Bird Conservation in Asia's Lowland Forests

The Khlong Phrasaeng Dam case study serves as a stark reminder of the ecological consequences of large-scale development projects. With thousands of new dams planned across Asia, the threat to bird biodiversity in lowland forests is only set to intensify.

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A Dam's Reported Impact on Local Birds

A study by an international team of conservation scientists reported that a dam built in Thailand 31 years earlier had caused the local bird population to collapse. This finding links dam development to a severe local wildlife impact, although the supplied source does not give a population count or identify the affected bird species. The report is evidence of an impact on birds near a dam, rather than a quantified estimate for Thailand as a whole.

The authors of the study emphasize the urgent need for careful planning and mitigation strategies to minimize the environmental impact of future dam projects. This includes conducting thorough environmental impact assessments, preserving critical habitats, and implementing conservation programs to protect threatened species.

Ultimately, balancing development needs with environmental protection is crucial for ensuring the long-term sustainability of Asia's rich biodiversity. By learning from the mistakes of the past and embracing sustainable practices, we can safeguard the region's unique ecosystems and the countless species that call them home.

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

Everything You Need To Know

1

How does dam construction affect bird habitats?

The construction of dams, like the Khlong Phrasaeng Dam, leads to significant habitat loss. When a river is dammed, the resulting reservoir floods large areas of forest. In the specific case of the Khlong Phrasaeng Dam, this flooding submerged 165 square kilometers of forest. This direct habitat loss is a major cause of the decline in forest bird populations because it removes the places where they live, breed, and find food. Forest-dependent species, those specifically adapted to the forest environment, are particularly vulnerable, leading to their displacement or even local extinction.

2

What is species displacement, and why is it a problem?

Species displacement is a critical consequence of dam construction and environmental transformation. Many bird species are adapted to specific ecological niches within the forest. When the environment changes due to factors like flooding and habitat degradation, these specialized species may not be able to adapt. The research, as demonstrated at the Khlong Phrasaeng Dam, shows that some bird species found in undisturbed upstream habitats have disappeared from the area after the dam's construction. Common, adaptable species often thrive in the altered environment, leading to increased competition that further threatens native birds. The rail babbler is an example of a species that has been lost due to these environmental changes.

3

What specific impact did the Khlong Phrasaeng Dam have on the environment?

The Khlong Phrasaeng Dam serves as a clear illustration of the impact that these development projects can have on bird biodiversity. The dam, constructed in 1986, caused significant ecological disruption, including habitat loss, species displacement, and increased competition among bird species. The study compared bird populations in the areas around the dam, and those on the reservoir islands. It revealed a decline in the diversity of birds in the degraded habitat. The impacts are particularly concerning when considering the numerous dams planned throughout Asia, and the potential for widespread ecological consequences.

4

What are sustainable development practices?

Sustainable development practices are essential to protect bird biodiversity in areas undergoing rapid development. The study underscores the need for developers and governments to consider the environmental impact of their projects. This could involve measures such as comprehensive environmental impact assessments before dam construction, the implementation of mitigation strategies, and the preservation of critical habitats. Given that thousands of new dams are planned across Asia, adopting sustainable practices is important to minimize the impact on bird populations and other wildlife.

5

What can be done to conserve bird populations in the face of development?

The research highlighted the urgent need for conservation efforts to protect forest bird biodiversity. It is important to mitigate the negative impacts of dam construction and broader development. Conservation can take many forms, including habitat restoration, protected areas, and strategies to reduce competition between bird species. Studying the consequences of projects like the Khlong Phrasaeng Dam provides insights for future conservation strategies. The aim is to protect vulnerable bird species and the ecosystems they depend on, given the increasing pressures from development across Asia's lowland forests.

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