Sand mining threatens the way forward for essential SE Asian ecosystem

Published:


2025-11-11 10:23:00

Intense sand mining is placing the biggest freshwater lake in Southeast Asia liable to collapse with catastrophic penalties, a brand new examine has discovered.

The big Tonlé Sap Lake in Cambodia, a

UNESCO Biosphere Reserve

, is likely one of the world’s most ecologically numerous lake ecosystems, residence to endangered amphibians, reptiles, mammals and birds, with a various array of 885 species. It gives livelihoods for nearly two million fishers, and its fish feed hundreds of thousands extra.

But its future is at risk because the depth of the distinctive ‘reverse flow’ that feeds water into the lake has been declining year-on-year.

Scientists have now conclusively decided the reason for this decline to be sand mining within the Mekong River in Cambodia and Vietnam.

Sand mining is the observe of extracting sand from the riverbed, with the bulk used within the building trade.

Rates of sand mining within the Mekong have quickly elevated, with over 100 million tonnes of sand now being eliminated yearly.

Steve Darby, Professor of Physical Geography on the University of Southampton and co-author of the brand new analysis, mentioned: “There has been plenty of hypothesis as to why the depth of the reverse movement has been declining, with local weather change and damming on the Mekong upstream in China and Laos beforehand being recognized as doable causes.

“Our work demonstrates that, while climate change and damming are minor contributory factors, by far the dominant driver has been riverbed incision caused by largely rampant sand mining on the Mekong.”

The reverse movement system

Tonlé Sap Lake is sustained by an uncommon reverse movement system. The Tonlé Sap River usually drains the lake, flowing downstream to Phnom Penh, the place it joins the Mekong River.

But, through the monsoon season, the Mekong’s flood pulse rises excessive sufficient to power the Tonlé Sap River to reverse for a number of months, filling the lake.

The Tonlé Sap Lake shops a lot water throughout this seasonal flood pulse that it acts as a large ‘flood capacitor’, regulating flood water ranges down throughout the Mekong Delta – residence to 23 million folks – earlier than releasing the saved freshwater again downstream to the Delta through the dry season.

The examine, printed in

Nature Sustainability

, reveals that between 1998 and 2018, riverbed decreasing of the Mekong River mainstem, pushed by sand mining and upstream sediment trapping, has diminished the reverse movement volumes by between 40 and 50 per cent.

Projections to 2038, with further riverbed decreasing pushed by ongoing sand mining, recommend that the reverse movement might decline by as much as 69 per cent in comparison with 1998.

Dr Quan Le, Research Associate in Delta Flood Risk at Loughborough University and lead writer of the examine, mentioned: “Rapid city development has fuelled a worldwide surge in a requirement for building sands, rising river sand mining charges.

“Our study finds that this intensive sand extraction, combined with sediment being trapped by dams in the Lower Mekong basin, has already weakened the Tonle Sap lake’s flood pulse, causing lasting environmental harm and underlining an urgent need for sustainable sediment management to ensure that these future projections are not realised.”

On common, riverbed ranges throughout a lot of the Lower Mekong’s course in Cambodia and Vietnam have dropped by two to 3 metres within the final 20 years.

“At this rate, within 10 years the system is at risk of a near total collapse,” mentioned Professor Darby. “The Mekong is the second most biodiverse aquatic ecosystem in the world, after the Amazon, and its health depends on the normal functioning of the Tonlé Sap Lake. A collapse of the lake system would have catastrophic consequences for the biosphere, for millions of people’s livelihoods and food sources, and for flooding in the region.”

Understanding and mitigating the affect

Scientists are persevering with to evaluate the implications of sand mining within the area.

A undertaking known as

Hidden Sands

, led by Professor Julian Leyland on the University of Southampton, is investigating the affect of sand mining on the surroundings and on communities in Cambodia. The workforce has additionally been working with companies in Vietnam to offer a extra risk-based method to the governance of sand mining.

Along with the above researchers, Craig Hutton, Professor of Sustainability Science and director of the Sustainability and Resilience Institute, and Paul Kemp, Professor of Ecological Engineering, each on the University of Southampton, are embarking on a brand new undertaking to completely perceive the ecological affect on Tonlé Sap Lake, significantly the affect on fish.

Professor Hutton mentioned: “The lake is estimated to feed about six million people and provide as much as 60 per cent of Cambodia’s protein. The disruption in lake levels from sand extraction along with deforestation, illegal fishing and extreme pesticide and fertiliser use are exacting a heavy toll on fish production. This decline is threatening both food security and livelihoods.”

Professors Hutton and Kemp interviewed fishing communities in a current go to to the area.

“Struggling fisher folk have seen as much as an 80 per cent mortality in aquaculture fish, declines in wild catch and mounting household debt,” mentioned Professor Hutton. “One interviewee told us, ‘We just want another life for our children now. Anything but fishing’.”