Tonle Sap Lake is one of the most productive freshwater ecosystems in the world. But overfishing, climate change and plans to build a hydropower dams could threaten the animals that make their home in the body of water known as the beating heart of Cambodia. Hari Sreenivasan narrates a report in partnership with the Pulitzer Center on Crisis Reporting on efforts to track and maintain lake health.
JUDY WOODRUFF: Now to Cambodia and an inside look at efforts by U.S. scientists to save a critical water system.
This report, prepared by journalists Chris Berdik and Steve Sapienza and narrated by our Hari Sreenivasan, was produced in partnership with the Pulitzer Center on Crisis Reporting.
HARI SREENIVASAN: Dawn on Cambodia’s Lake Tonle Sap, Southeast Asia’s largest lake and one of the most productive freshwater ecosystems in the world.
Fisherman Keo Mao starts his day much like his neighbors, with family breakfast. Then the father of five paddles a nearby mangrove to reach the gillnet he set the night before. Mao and others catch about 350,000 tons of fish from this lake every year, a vital resource in a country where 75 percent of the protein people eat is fish.
At a nearby fish landing, workers sort the day’s catch. Most of the haul is minnows, known as trey riel, or money fish, which go for 25 to 50 cents a kilogram. They’re used to make fermented fish paste called Prahok, a staple in Cambodian cooking.
The importance of fish is deeply rooted in the Cambodian culture. Chiseled into the medieval temple of Angkor Wat are many of the same fish that are harvested from the Tonle Sap today.
The astounding number and diversity of fish here has long attracted researchers, like American biologist Les Kaufman.
LES KAUFMAN, Boston University: I have never seen the color pattern on this guy. It’s really cool.
HARI SREENIVASAN: Kaufman is a fish savant and clearly enjoys every second he spends on the water.
LES KAUFMAN: Hey.
HARI SREENIVASAN: There are plenty of small fish at this landing, but what worries Kaufman is what he doesn’t see.
LES KAUFMAN: This is the most productive inland fishery in the whole world. And yet we have seen most of the large fish disappear from the lake, Mekong giant catfish, the giant stingray, the giant nightfish. All these fish are disappearing. And that’s an obvious sign that overfishing is taking a toll.
HARI SREENIVASAN: To protect the fishery from growing numbers of fishermen, the lake is now divided into hundreds of community-managed fisheries along with newly formed conservation areas.
But illegal fishing is common, and most villages lack the resources to stop it.
KEO MAO, Akol village, Cambodia (through interpreter): When villagers here are fishing with nets use, they about 200 meters, but the outsiders who come here use bigger nets and catch lots of fish.
HARI SREENIVASAN: At the edge of Mao’s village, rangers ready boats to patrol the nearby conservation area.
SAM-AT, Inland Fisheries Ranger, Lake Tonle Sap (through interpreter): From January to early February, we confiscated fishing nets, some 8,860 meters, and we destroyed them.
HARI SREENIVASAN: Out on the lake, the patrol boat picks up speed. The rangers have spotted some fishermen who have slipped into the reserve. Their boat is intercepted and search for illegal fishing gear. The nets are legal, so the rangers simply escort them out of the reserve.
SAM-AT (through interpreter): We took them to our office and made a report, informing them about fishing legally outside the preservation area.
HARI SREENIVASAN: Overfishing is just one threat to the Tonle Sap.
LES KAUFMAN: Cambodia is a developing nation, a rapidly developing nation. It has enormous promise, tremendous potential, but the problem is that it’s developing without a clear plan that acknowledges the tradeoffs.
HARI SREENIVASAN: Often called the beating heart of Cambodia, the Tonle Sap is powered by a massive annual pulse of water, flooding and receding in the lower Mekong River Basin, to which it’s connected by the Tonle Sap River.
Today, the flooded forests and nursery for young fish are being cut down for cooking fuel and farmland. A change in climate will likely bring more extremes of flood and drought. And scientists worry that plans to build more than 100 hydropower dams upstream on the Mekong, dams that would generate power for the growing economies for the region, could cut off both the flood pulse and fish migration.
Kaufman and an international group of scientists are working with local fishermen and Cambodian authorities to solve this puzzle. Kaufman’s modeling work began five years ago with the coastal ecosystems of Massachusetts. Now he and his colleagues are in Cambodia to develop a massive dynamic computer model of the lake’s ecosystem.
LES KAUFMAN: We have been working together to try and get a big-picture view of the possible alternative futures for the Tonle Sap and the wider lower Mekong.
HARI SREENIVASAN: Local fishermen like Keo Mao are also part of the effort. He works part-time for the NGO Conservation International to track the health of the lake. He collects fish from sampling nets, records the species, size and weight, and snips off a bit of the tail for DNA analysis.
The samples collected by Mao and others will help the researchers construct a Tonle Sap food web, which will become the basis for algorithms of what eats what in the ecosystem model. Kaufman believes ecosystems are networks of relationships between living things and the habitat they share. That includes humans, who are part of the ecosystem and profit from its continued health.
LES KAUFMAN: So what we’re trying to do is tread a central path, where we don’t forget that preserving the wealth of creation is critical to human survival in the long term, and, at the same time, we don’t forget that food and jobs immediately are what people are looking for right now.
HARI SREENIVASAN: Villagers who live in the flood zones of proposed hydropower projects are already facing tough choices. As designed, one new dam will be almost 250-feet high, and its reservoir will flood dozens of villages, forcing nearly 5,000 people to resettle.
Dense broad-leaved forest once flanked this road to the Kbal Spean, one of the villages that will be underwater when the dam is built. This area was recently clear-cut for a rubber tree plantation. Villagers, like 61-year-old Te Samm, have been asked to move in exchange for compensation, but they’re resisting.
During the terror-filled reign of Khmer Rouge, her village was ordered at gunpoint into the countryside, where they became forced labor, planting rice and digging irrigation canals.
TE SAMM, Kbal Spean village, Cambodia (through interpreter): During the Pol Pot regime in 1976, we were evacuated to this northeast region.
HARI SREENIVASAN: She was asked about moving again to make way for the dam.
TE SAMM (through interpreter): I think I wouldn’t be alive if they moved me to a new location. I do not think I would survive.
HARI SREENIVASAN: Villagers who live upstream from the proposed dam do not face relocation. Instead, they’re worried about flooding and declining fish stocks.
WA KHAM PHAI, Kbal Spean village, Cambodia (through interpreter): Right now, we have lots of fish. But if they block the river with the dam, fish will not be able to migrate here.
HARI SREENIVASAN: Cambodia needs more power to fuel its emerging economy and ease widespread poverty. But it also needs the fish, clean water, and the biodiversity of the Tonle Sap.
LES KAUFMAN: By selecting one dam site over another, it can make an enormous difference in the ability of the fishes to spawn, and that could be 30 or 40 percent of the fish biomass for the whole future out of Tonle Sap.
HARI SREENIVASAN: There’s no guarantee of success. But as the planet warms, the dams rise, and more fish vanish, Kaufman and his colleagues also believe that the time for wise decisions is now.
JUDY WOODRUFF: To find out more about the future of Lake Tonle Sap, visit our Web site, where you can find links to Chris Berdik’s articles on the water system for The New York Times and the Virginia Quarterly Review.