Hydropower dams planned for the lower mainstem of the Mekong River could decimate fish populations and with them the primary source of protein for 60 million people. The impact of the dams would extend far beyond the river, as people turn to agriculture to replace lost calories, protein and micronutrients, according to a new study by WWF and the Australian National University.
There are 11 planned dam projects on the Mekong mainstem, and another 77 dams planned in the basin by 2030. The study, “Dams on the Mekong River: Lost fish protein and the implications for land and water resources”, looked at two scenarios: replacement of lost fish protein directly attributable to the proposed 11 mainstem dams, and replacement of the net loss in fish protein due to the impact of all 88 proposed dam developments.
If all 11 planned mainstem dams were built, the fish supply would be cut by 16 per cent, with an estimated financial loss of US$476 million a year, according to the study. If all 88 projects were completed, the fish supply could fall 37.8 per cent.
Study co-author Stuart Orr, freshwater manager at WWF International, says policymakers often fail to recognize the crucial role of inland fisheries in meeting food security. “The Mekong countries are striving for economic growth, and they see hydropower as a driver of that growth. But they must first fully understand and take into account the true economic and social value of a free-flowing Mekong,” says Orr.
The lower Mekong, flowing through Cambodia, Laos, Thailand and Viet Nam, is renowned for its biological diversity, with more than 850 freshwater fish species. These fish are fundamental to diets and economies in the region, with 80 per cent of the 60 million inhabitants relying directly on the river for their food and livelihoods.
The report also looks at the effects on land and water as people are forced to shift to cows, pigs, poultry and other sources to meet their protein requirements. On top of 1,350km2 of land lost to dam reservoirs, the countries would need a minimum of 4,863km2 of new pasture land to replace fish protein with livestock. The high end of the estimate if all dams were built is 24,188km2 – a 63 per cent increase in land dedicated to livestock.
Water requirements would jump on average between 6 and 17 per cent. But these averages mask the considerably higher figures for Cambodia and Laos. Under scenario one, with 11 dams on the mainstem, Cambodia would need to dedicate an additional 29-64 per cent more water to agriculture and livestock; Laos’ water footprint would increase by 12-24 per cent. Under the second scenario, with all 88 dams, these numbers shift dramatically, with an increase of 42-150 per cent for Cambodia and 18-56 per cent for Laos.
“Policymakers in the region need to ask themselves where they are going to find this additional land and water,” says Orr. “The Mekong demonstrates the links between water, food and energy. If governments put the emphasis on energy, there are very real consequences for food and water – and therefore people.”
The report, published in the journal Global Environmental Change and presented during World Water Week in Stockholm, comes at a critical time in the debate over hydropower development in the region. Construction work appears to be moving ahead on the controversial Xayaburi dam in Laos, despite a decision by the intergovernmental Mekong River Commission to halt the project pending further studies. It would be the first of the planned dams to span the lower Mekong mainstem.
“We hope this study can help fill some of the knowledge gaps about the effects of the proposed dams,” says co-author Dr Jamie Pittock from the Crawford School of Public Policy in the Australia National University.
WWF urges the lower Mekong countries to defer a decision on the mainstem Mekong dams for 10 years to ensure critical data can be gathered and a decision can be reached using sound science and analysis. WWF further advises lower Mekong countries considering hydropower projects to prioritize dams on some Mekong tributaries that are easier to assess and are considered to have a much lower impact and risk.
An abstract of the study, with the option to download the full text, is available here: