The dams built along Mekong River and its tributaries are posing a threat to the survival of bird species. Unnatural flooding and erratic river flow of Mekong caused by these hydropower dams, have resulted in loss of habitats, making it difficult for the birds like the Saurus cranes and Bengal Floricans to breed.
Since 1995, there are 11 hydropower dams along upstream Mekong within China’s borders and another 11 in Laos and Cambodia on the mainstream, along with hundreds of dams on its tributaries.
Hydropower dams have had a drastic effect on the Mekong River: unseasonable flooding and droughts, low water levels in the dry season, and drops in the amounts of sediment carried by the river, with extreme consequences for biodiversity.
“Any changes to the Mekong River will definitely affect the river’s tributaries and wetlands adjacent to it,” says Pianporn Deetes, communications director for Southeast Asia at International Rivers. She adds that the Mekong is a complex system in which different ecosystems are connected. “As the river is dammed upstream, the entire ecosystem is cut off and disrupted.”
The “Bastards of Asia”
Every year, the Mekong floods forces the Tonle Sap Lake in Cambodia to swell five times its low-water size and thus creating the largest lake in Southeast Asia. However, in 2019, a combination of climate change, El Niño and dam operations left the lake with record low-level of water, warm, shallow and oxygen starved.
Combined with the practice of burning surrounding scrubland and grassland for farming, the loss of habitat in Tonle Sap Lake endangers a number of bird species which breed in the area, such as the Bengal florican.
The Bengal Florican, also known as the “Bastard of Asia”, is considered critically endangered by the International Union for Conservation of Nature (IUCN). “This species is considered critically endangered and is now almost entirely restricted to the Tonle Sap floodplain,” the IUCN stated.
Cambodia’s population of Bengal florican has sharply declined since 2012, according to a survey conducted by the Wildlife Conservation Society (WCS) and the Ministry of Environment.
The Bengal Florican’s fate has been closely tied to the beating heart of Mekong, the Tonle Sap floodplain. In dry season, the northern Tonle Sap is very important for the Bengal Florican hatchery area, while the northern forest of Tonle Sap is the main habitat areas during the rainy season.
According to the Environment Ministry spokesman, Neth Pheaktra, “the Bengal Florican are regarded as one of rarest species in the world and the drop in the population in Cambodia is very worrying. We need to enforce protection measures in conservation areas from every relevant sector. It is essential to the survival of this species.”
Sum Phearun, Technical Advisor at Wildlife Conservation Society (WCS), said: “We need to do everything we can to save the Bengal Florican in Cambodia. Protecting inundated natural grassland in the Tonle Sap floodplains is the key action to ensure species recovery and its long-term survival.”
Decline of the tallest bird in the world
One of the most iconic bird species of the Mekong floodplains would be none other than the Saurus crane. At 176 cm (just under 6ft), the Sarus crane is the tallest flying bird and is classified as vulnerable on the IUCN’s red list of threatened species.
According to the World Wildlife Fund (WWF), the Indochinese subspecies has declined dramatically, and less than 1,000 birds are now confined to Cambodia, extreme southern Laos, southern Vietnam, and Myanmar.
According to WCS Cambodia, Sarus cranes were previously widely distributed across South and Southeast Asia but have undergone rapid population declines due to widespread hunting, egg collection and habitat loss.
Sarus cranes in Cambodia are highly vulnerable. They breed in the dry deciduous forests and associated wetlands along the floodplains of the Mekong and its tributaries during the monsoon. Towards the dry season, they move downstream to settle in the wetlands along Tonle Sap Lake, as well as several wetlands on the upper Mekong delta spanning the Cambodia-Vietnam frontier.
Other than the iconic Mekong birds, other lesser-known bird species such as the Grey-throated martins, a swallow species, have also been on the decline. The swallows used to make their home in the fertile area where the Ruak River meets Mekong, the border between Thailand and Myanmar.
“It still really depends on investors or developers (of dams) to address the problem and solve it,” says Deetes. “They need to understand the nature of the river, its system, and the impacts they can cause.”
“The fact is the dams are far away, but their impacts are here and real,” says Chanruang, Chair of Boon Rueang Wetland Forest Conservation Group. “We are always concerned about them but we can never reach them and deal with them directly.”
Photo credit: iStock/Tanes Ngamsom