The downstream impacts of dams on the seasonally flooded riverine forests of the Mekong River in northeastern Cambodia

ABSTRACT

On the Mekong River, north of Stung Treng town in northeastern Cambodia, and below the border with Laos, lies an area of riverine seasonally flooded forest designated as an internationally significant Ramsar wetland site because of its exceptional biodiversity and importance to livelihoods. This article reports on the cumulative and cascading impacts of numerous upstream hydropower dams in China and Laos on this vital ecosystem due to the release of water during the dry season, which prevents the flooded forest from undergoing its critically important drying out period. In particular, we investigate the damage being wrought on these flooded forests and on the various species dependent on them. Different species have been variously affected, but some have been largely destroyed. Others are being increasingly impacted. This habitat loss is negatively affecting fisheries, especially for a number of Pangasiidae catfish and Cyprinid carps, which is having an adverse effect on local livelihoods. New dams upriver, and continued high dry-season water from existing dams, are likely to lead eventually to the increased degradation and possibly the eradication of the flooded forests along the mainstream Mekong River, unless measures are taken to address the problem.

KEYWORDS:

• Mekong river
• Flooded forests
• Hydropower dams
• Downstream impacts

Acknowledgements

Thank you to Bun Sithon for assisting us with fieldwork in 2022 and to other villagers who supported our research in Stung Treng Province. Brian Eyler, Jake Brunner, Andrea Claassen and Zeb Hogan provided some useful information and comments on earlier drafts. Ratha Sor helped identify one of the molluscs reported on in this article. This research was funded by the Center for Khmer Studies, and the project, Tracking Change: Local and Traditional Knowledge in Watershed Governance, which was funded by the Social Sciences and Humanities Research Council (SSHRC) of Canada in a grant to Parlee-University of Alberta (SSHRC PG 895-2015-1024 Parlee). Thanks to Bryce Linden from the Cartography Lab in the Department of Geography, University of Wisconsin–Madison for helping prepare the map.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 Energy Consumption in Laos https://www.worlddata.info/asia/laos/energy-consumption.php, accessed 16 May 2023.

2 There is potential to use remote sensing to estimate the amount of flood forest that has died, but this research has so far not been conducted.

3 Although the hydrological data collected today is likely to be more accurate than that collected during the French colonial period and the early post-colonial period, the data presented have not been reported to be egregiously inaccurate.