Reconciling People and Nature on Cambodia's Tonle Sap
ANGKOR THOM, CAMBODIA (29 November 2004)- Stone carvings at the ancient Bayon temple show that water and fish from the nearby Tonle Sap (Great Lake) helped sustain an Angkorian empire that stretched well beyond its jungle capital.
Today, Asia's largest freshwater lake - and its unique ebb and flow - nourishes a community far larger than the 2.9 million Cambodians who live around it. Fish that migrate from the lake to other parts of the Mekong River basin sustain the rapidly growing population of mainly poor rural inhabitants of the flood plains.
But the lake is in deep crisis.
"Never has the lake been called upon to supply so much to so many, yet threats to its ecosystem are manifold," says Olivier Serrat, an ADB senior project economist who developed ADB's Tonle Sap Basin strategy.
Increasing demands on its land, water, and biotic resources are threatening the lake's fragile ecology.
The stakes are high, for its fisheries provide the single biggest source of protein for Cambodia's young and increasing population.
The lake is also the flood retention basin for the Mekong River, one of the world's longest waterways that threads through six countries of the Greater Mekong Subregion (GMS) along its 4,800-kilometer (km) course from the glaciers of Tibet to the warm waters of the South China Sea. These are Cambodia, People's Republic of China (PRC), Lao People's Democratic Republic (Lao PDR), Myanmar, Thailand, and Viet Nam.
Amid a complex Mekong system, the relationship between river and lake is akin to that of a body and its lungs. This manifests itself in a remarkable natural phenomenon every monsoon. When the rain-swollen Mekong River merges with the Tonle Sap River at Phnom Penh, it pushes floodwater back into the lake. This raises the level of the Tonle Sap by up to 10 meters, increasing its area from between 2,500 and 3,000 square kilometers (km2) in the dry season to between 10,000 and 16,000 km2 in the rainy season.
This unique hydrological cycle floods vast areas of low forest and shrubs and creates a rich biodiversity of fish, reptiles, birds, and mammals. It also saves large urban centers and vital infrastructure from being inundated.
The flow of the Mekong River helps determine how much the Tonle Sap expands in the wet season. Earlier this year, the river's water levels were at their lowest for 2 decades - the Mekong River Commission (MRC) says this was mostly due to a prolonged drought. The MRC notes that the river's level has fallen slightly over the past 20 years, but adds that there has also been frequent extreme flooding in recent years.
The lake is not only a reservoir but also a giant nursery for the Mekong River. Fish spawned in the lake's flooded forests and vegetation during the monsoon migrate to the Mekong River in the dry season. These fish are a regional resource, traveling upstream, some say, as far as the PRC as well as downstream to the Mekong Delta. Thus, the lake is the source for much of the river's biodiversity as well as productivity.
Importantly, the water draining from the Tonle Sap also improves dry-season conditions by limiting tidal influences in the Mekong Delta. Keeping the sea at bay helps control the rate of saline intrusion into a vitally important agricultural area that is Viet Nam's rice bowl.
"Threats to the lake include overexploitation of fisheries and wildlife," says Mr. Serrat. "In the dry season, foraging and land clearing have reduced forests that, when flooded, act as a natural habitat for fish to breed. This has led to deterioration in water quality, as well as increasing siltation."
All this means tough times for those who live by fishing or foraging on the lake. Between 40% and 60% of these people subsist below the poverty line.
The fishing community at Chong Kneas, a crowded and unsanitary landing point in the northern part of the lake near Siem Reap, is reporting steep declines in fish catches and income.
Sitting with his wife in a houseboat with holes in its thatched roof, Touch Sophat recalls earlier times of plenty.
"When we moved from Battambang in 1979 after the civil conflict, the lake had so many fish people joked that the fish would jump into your boat or that the fish ate the people."
Today, it is no laughing matter. "We used to catch at least 300 kilograms of fish a day. Now it can be as little as 20 kilograms," says his wife, Yim Pha, who gets up before daybreak to tend the nets and sells the catch in the market in the late afternoon.
"Our income has dropped a lot," she says. "We have to spend on schooling, on food, on oil. You can see our houseboat needs repair, but we have no money even for medicine or clothes for the children."
She and her husband, who is deputy headman of the community, share the houseboat with their nine children.
As a result of a sharp drop in income, many who have spent their lives in this floating village now want to settle on land.
Chong Kneas reflects many of the challenges facing the lake.
A rapid rise in population is a major cause for declining catches among small-scale fisherfolk. "When we arrived, there were 300 families in this community. Today, we have more than 1,100 families," says Mr. Touch.
The subsistence fishers also face competition from large-scale commercial enterprises. The competition has encouraged illegal fishing methods, such as the use of fine-mesh nets, dynamiting, and cyanide poisoning.
Falling water levels and climate change can also affect supply of fish stocks. "Before, there were many big fish, such as the giant snakehead," says Mr. Touch. "Now what's left are mostly small fish."
At Chong Kneas, ADB may provide assistance to encourage a community approach toward fishing as well as to build a permanent harbor/township on a raised platform of land.
"At Chong Kneas and other locations, we are promoting a community approach toward managing fish and other natural resources," says Ian Fox, Principal Project Specialist (Natural Resources) in ADB's Mekong Department. "This includes helping regenerate forests, establishing fish sanctuaries, and policing against illegal fishing methods."
For the lake as a whole, ADB has drawn up a basin strategy that will prioritize assistance over the next 5-10 years.
ADB is also playing a key role to strengthen the regulatory and management framework and institutional structures at local and national levels. This includes a basin management organization.
Beyond the lake, its umbilical relationship with the Mekong River underscores the need for regional resource cooperation among the six countries sharing the river.
A coordinated approach is essential because of many conflicting demands on the river and lake: for agriculture, fish, water, transport, biodiversity, and hydropower.
MRC and ADB agree that governments need to cooperate to balance development with protection of natural resources and biodiversity. Trade in timber and wildlife, including endangered species, also threatens biodiversity.
"To get the right balance, there must be a strong cooperation and negotiating mechanism in managing different interests and viewpoints," said Dr. Olivier Cogels, MRC's Chief Executive Officer, at a recent meeting in the Lao PDR capital, Vientiane. "Involvement of government, private sector, and civil society stakeholders on all levels is fundamental to achieving this aim."
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