Is Southeast Asia’s Largest Lake Dying?

Is Southeast Asia’s Largest Lake Dying?

Why you should care

Because the world’s next climate conflict could be here.

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Geo facts & figures

During the monsoon months, Tonle Sap expands as if inhaling, fed by a Mekong River so engorged with water that it changes direction. When that happens, the lake — the largest in Southeast Asia — can spread to five times its size compared to the dry season, enriching the soil of surrounding farmland and creating a route for migratory fish. This yearly rhythm, called a flood pulse, has earned the lake its nickname, Cambodia’s “beating heart.”

But if that’s the case, then Cambodia has heart disease. A combination of overfishing, dam construction and drought that some experts think is caused by climate change has altered the Tonle Sap ecosystem, making it less reliable, less productive and more vulnerable. In fact, according to a 2016 Global Nature Fund report:

Tonle Sap, which provides Cambodia with 75 percent of its protein, is the world’s most threatened lake.

It’s an ecosystem at a tipping point in a country that also is at a political crossroads. And no one is certain what will happen in the natural or political spheres. But when it comes to the stressed lake, some are taking a guess.

Kevin McCann, an ecologist from the University of Guelph in Ontario, has been studying Tonle Sap for more than five years, mapping its complex ecosystem. The lake is “a classic example of fishing down the food web,” he says. The big, slow fish populations have been decimated. What’s left are mostly small, rapidly producing species. Diversity has dropped to the point where the lake resembles a monoculture, like a cornfield. Fishermen still can land a big catch, but what’s in the net is of the smaller variety. Although productivity remains stable, the haul is worth less.

According to some scientists, if the 2,600-megawatt Sambor Dam in Kratie province proceeds, it will doom the freshwater fishery.

“You can’t go on forever like this,” says McCann. “There’s going to be a real threat of collapse.” It would resemble fish slipping out of a net — slowly at first and then all at once. Nature is “crazy resilient,” McCann says, but Tonle Sap might be heading into an irreversible decline.

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Fishermen in Prek Tol, Cambodia.

Source Nicolas Axelrod / Ruom

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Villagers in Chnouk Trou fish markets on the Tonle Sap, Cambodia.

Source Nicolas Axelrod / Ruom

Cambodia’s political environment is looking like a monoculture too. The ruling Cambodian People’s Party, led by strongman Prime Minister Hun Sen, has been in power for more than 30 years. And just this year it dissolved the largest opposition party. The dissatisfied are now the disenfranchised. The country’s politicians boast of having less than 1 percent unemployment, but this number counts anyone who works just one hour per week as employed. Many are underemployed, and, as in other fast-developing countries, inequality is rife.

The Cambodia scenario reminds Robert McLeman, an expert on environmental migration at Wilfrid Laurier University in Waterloo, Ontario, of other places in the world where environmental stressors led to political upheaval: the drought-ravaged Lake Chad basin in West Africa, the shrinking Aral Sea in Kazakhstan, the 1990s drought in Rwanda that some experts think contributed to the genocide there and the drought 10 years ago in Syria that sent young men from the parched countryside pouring into urban centers looking for work.

It’s usually the mobile youth who leave after the land stops providing. “It escalates the challenges cities and countries face in terms of trying to overcome social-economic inequalities,” McLeman says. In security circles it’s called a “threat multiplier.” Migration to urban areas itself won’t spin a region into conflict, but it can put pressure on housing prices, decrease wages and provide a high density of angry young men.

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Villagers prepare shrimp traps. Fish stocks accessible from this area have gotten so low that nearly everyone here catches shrimp instead.

Source Nicolas Axelrod / Ruom

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Kampong Luong, Cambodia. A chick rushes in to check for abandoned fish as a fisherman prepares to reset his net.

Source Luc Forsyth / Ruom

So far, the majority of Cambodians are still being fed by Tonle Sap. But three dams currently are being built in the Upper Mekong River, and some observers expect a flurry of additional hydropower projects when a hiatus on new dam construction expires in 2020. According to some scientists, if the 2,600-megawatt Sambor Dam in Kratie province proceeds, it will doom the freshwater fishery. The pulse that has nourished the waters and floodplain of Tonle Sap — and the people of Cambodia — for generations will be stilled. If and when that happens, the 80,000 people who live in floating villages on the lake and the 3 million residents of floodplain farming communities will have to find a new way to live.

Meanwhile, national elections are scheduled for the summer. It’s enough to pray for a wet monsoon season.

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Kampong Chhnang, Cambodia. Villagers in Chnouk Trou on the Tonle Sap.

Source Nicolas Axelrod / Ruom

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