Photo: Éric Desrosiers Le Devoir Uncle Hai in his rice field
Born from the union of land and water, the Mekong Delta is today threatened with disappearance, victim of the lack of attention paid to the fragile and complex functioning of nature. First article in a series of four.
Today, motorcycles, cars and trucks have replaced boats as the main means of transportation in the Mekong Delta in southern Vietnam. The increasingly wide and numerous roads, however, must constantly span the thousand and one streams, rivers and canals which streak the landscape through palm trees, plains and fields. In fact, when you look closer, you realize that even where you see all kinds of shades of green, water is also omnipresent, since there are also flooded aquaculture farms and rice fields.
While there are still a few fields with long, golden rice plants waiting to be harvested at the end of the rainy season, most of the rice fields have already restarted a new life cycle and are covered with small shoots of a soft green. Knee-deep in water at the end of a long field in the humid heat of December, Uncle Hai grabs plants with their clods of mud to throw them gently a little further away where they will have more 'space to flourish.
“Last year was bad, with all the floods,” said the middle-aged man with the sun-burnt face. This year promises to be much better thanks to the food crisis which has driven up world prices. Now let's hope there is no rain for the next three months. »
A delta threatened with disappearance
This peaceful spectacle, in the middle of lush nature, hides a drama with potentially catastrophic consequences. Indeed, the entire region is threatened with disappearance by the end of the century.
Built over millennia by the accumulation of sediments transported and deposited by the Mekong River and its tree structure of waterways, at the end of a long journey across six countries from the heights of the 'Himalayas, in China, to the South China Sea, in the south of Vietnam, the Mekong Delta is a fertile land where nearly 18 million people live.
- Overexploitation of sand resources in the Mekong Delta risks making it disappear
- Hard times for environmentalists in Vietnam
Nicknamed the “rice bowl” of Vietnam, with more than half of the national production on only 12% of the territory, it helps to feed the population of nearly 100 million inhabitants in addition to making it the third largest exporter of rice in the world, behind India and Thailand. Fruits and vegetables are also abundant there. Its rivers, coast and aquaculture farms have the second highest species diversity on the planet after the Amazon basin, with around a thousand different species, and give Vietnam the third largest species diversity in the world. shrimp exports and the first for pangasius exports.
But this Eden is, on average, less than a meter above sea level. And at the rate things are going now, 90% of its territory will have disappeared under the waters of 'by the end of the century, experts warned in 2022 in the scientific journal Science.
The fault of humans
It is the fault, of course, of climate change, with rising sea levels, erosion, flooding and destruction caused by increasingly frequent and violent typhoons , not to mention ever more extreme rainy and dry seasons. But it's mostly the fault of humans who do everything wrong, sometimes even when they try to fix things.
Indeed, if it is true that sea levels rise, on average, by around four millimeters each year, you should know that at the same time, “the Mekong Delta is sinking” 5 to 10 times faster depending on the location (from 1.2 cm to 2.5 cm), explains Brian Eyler, specialist in these questions at the research and action organization Stimson Center.
This is because, to go from a single rice harvest to three per year, we surrounded the fields with dikes to better control irrigation and protect against damage inflicted by seasonal floods and floods. The problem is that these floods also deposited a layer of sediment throughout the territory, raising the delta compared to sea level, in addition to acting as fertilizer. This great coming and going of the water also served as a natural mechanism for cleaning and disinfecting the soil which, like the sediments, had to be replaced by chemicals which inevitably ended up polluting the waterways.
It is also that this “pulse of the Mekong”, which beats to the rhythm of seasonal floods, is in the process of dying out with the proliferation of hydroelectric dams in China and elsewhere which regulate the flow upstream. What's more, these dams already retain in their reservoirs 50% to 70% of the sediments that once flowed down the current to be deposited in the delta and this proportion could reach 96% if nothing is done and the approximately 150 new dams under construction or planned are added to the fifty already existing.
“China argues that this is helping to reduce the damage inflicted by flooding downstream, but all the research shows that this damage was far less than the environmental and human damage caused by dams currently “, explains Brian Eyler.
To complicate matters a little more, Cambodia is toying with the project of digging a canal that would connect its capital, Phnom Penh, to the Gulf of Thailand, to the west. This would prevent these boats from having to go down the Mekong through Vietnam, but would also divert yet another part of the river's water.
Hungry water and fish
Fish are also affected. Dams not only prevent the migration of several species, they also retain sediments on which fewer and fewer wild fish can feed. The lowering of river beds with sand extraction and the reduction in their flow also allows seawater to enter deeper and deeper inland, disrupting the ecosystem.
It’s not just the fish that are hungry, explains Nguyen Huu Thien, an international expert and consultant on these issues for around thirty years. Freed from these sediments, the water flows down the current with more force and speed, which accelerates the erosion of the banks and carries away a growing number of houses and riverside infrastructure. “We call it starved water.”
An acceleration of erosion is also occurring along the coast. Indeed, the sediments and sand that were formerly transported to the sea not only contributed to an abundance of marine life and to the maintenance of the mangrove, they also created a sort of protective cushion around the delta capable of absorb part of the shock of typhoons, recalls Nguyen Huu Thien.
But all this fragile and complex balance is about to go out of whack, says with a sigh this son of a farmer who remembers the time when, as a child, he still dared to bathe in the stream next to his home and came out again. a fish for supper.
Today, wild fish fishing has largely been replaced in the Mekong Delta by aquaculture and land yield continues to decline. Fishermen like farmers who were unable to increase their production volume enough to earn a living sold everything to others and went to work in factories in the Ho Chi Minh City region.
“We had inherited a paradise. And we found a way to lose it within a generation. »
Solutions that complicate things
Engaged in increasingly intensive production at the same time as having to deal with a reduction, pollution and salinization of waterways, farmers began to frantically pump the water table. “The Mekong Delta is like a melon that is hollowed out from the inside. As it is emptied, it sinks,” bringing dangerously closer to the time when it will be lower than sea level, explains Nguyen Huu Thien.
To protect itself from this threat, Vietnam has already built a set of 10,000 dikes and is increasingly isolating its delta from the sea. This is what was done in the Netherlands and in the Mississippi delta, in the USA. But it is a solution that is excessively expensive, particularly for a developing country, says the expert. Furthermore, we would end up completely cutting off any supply of sediment and sand to the coasts, which would thus find themselves bathed in “desert water. »
“For a long time, we have attributed the problems of the Mekong Delta to climate change,” observes Marc Goichot, head of the water program of the World Wide Fund for Nature (WWF) for Asia-Pacific. “It was very practical, because it was an external phenomenon. It becomes more complicated when we admit that climate change is only one of the causes of the problem, but also simply an indicator of other human factors. »
“We must start by recognizing our mistakes, discarding this image of humans in control of nature, and looking for ways to rebuild the resilience of the system we have weakened,” says Nguyen Huu Thien.
This will have to involve, among other things, stopping the unbridled construction of dams and better management of those that already exist, indicates Marc Goichot. The matter will not be easy, because it will require cooperation between six countries with not always concordant interests and problems.
The Franco-Canadian based in Ho Chi Minh City nevertheless says he is encouraged by the initiatives recently deployed by the governments of the region which have finally started, for example, to document the reserves of sediment and sand available and what is happening to them . “It may seem elementary, but it has never been done. Scientific understanding of most of these phenomena remains very recent. She's not ten years old. When we know this, and we see what is being done elsewhere in the world, I would say that the response of local authorities is even exemplary. »
“Who knows? said Nguyen Huu Thien. Perhaps it is not too late for me to be able, one day, to return to my village and swim there like when I was little. »
This report was financed with the support of the Transat International Journalism Fund-Le Devoir.