Facts and figures

Tonle Sap is a vast seasonal lake in the centre of Cambodia connected to the Mekong River by the Tonle Sap River. For most of the year the lake is fairly small, around one meter deep and with an area of 2,700 square km. However, during the monsoon season the Tonle Sap River reverses its flow as water is pushed up from the Mekong River into the lake, increasing its area to 16,000 square km and its depth to up to nine meters, flooding nearby fields and forests.

This pulsing ecosystem with its large floodplain, rich biodiversity, and high annual sediment and nutrient fluxes from the Mekong makes the Tonle Sap a globally significant site of biodiversity. Its ‘flooded forests’ povide habitats for more than 200 plant species; 200 fish species, including rare fish such as the Giant Catfish and the Mekong freshwater stingray; 42 reptile species including crocodiles, turtles, terrapins and tortoises, and 15 mammal species, including ten species of global significance.

The Tonle Sap is also one of the most productive inland fisheries in the world, supporting over three million people and providing an annual fishing yield of 230,000 tons, over 75% of Cambodia's annual inland fish catch and 60% of the Cambodians' protein intake. Although the value of this catch is about $100 million per annum little of the money finds its way into the local economy, as (until recently) the majority of fishing areas were leased out, leaving local fishers marginalized.

Today, about 1.2 million Cambodians live in the area of maximum flooding around Tonle Sap. A quarter of them live in 170 floating villages on the lake or on the floodplain, in houses built on poles. The population of the Tonle Sap sub-catchment area is estimated at three million, many of whom derive at least part of their subsistence needs or income from the lake’s resources.

Cultivation covers 23% of the floodplain, extending over 350,000 ha. Much of this is rice, along with mungbeans, melons and a wide range of other vegetables that are planted as floodwaters recede. The wetlands produce 450,000 tons of rice per year or 12% of Cambodia’s total production. Although the flooded forests produce no timber of commercial value they are a rich source of firewood and charcoal, construction material, and non-timber forest products such as honey, rattan, snakeskin and meat. The region has significant potential for tourism development, with the number of international arrivals tripling between 1993-2000. Visitors to the Angkor temple complex at Siem Reap alone number 20-30,000 per year.

Although Tonle Sap was designated a biosphere reserve by Royal decree in 2001, its biodiversity faces increasing pressure. Threats include over-exploitation of forest resources due to the high domestic and industrial demand for cheap, locally available fuelwood and charcoal, construction materials for houses and fishing gear. Increased demand for agricultural land, dry season burning, and increased large-scale seasonal influx by migrants are leading to creating dry season encroachment and land clearance of flooded forests, resulting in a direct loss of habitats. There has been an increase in domestic waste, untreated industrial effluents, use of agrochemicals, and discharges and spillage of oil and fuel.

Annual fish catch levels at Tonle Sap have remained fairly constant until recently but there are clear indications that over-exploitation of resources has led to a decrease in numbers of key species (including the threatened Mekong giant catfish), relative sizes of fish being caught, and a shift in species composition.

The native flora and fauna of Tonle Sap are also threatened by alien invasive species which come from accidental release/escape of exotic fauna from farming or culture operations, and the uncontrolled and unmonitored spread of exotic flora, in particular giant mimosa and water hyacinth. A general lack of awareness of the need to control and manage exotic species and a complete lack of eradication procedures or management programs is exacerbated by the high economic returns offered by farming exotic wildlife species.

Over-exploitation of wildlife resources in the Tonle Sap is having a direct negative impact on many wildlife species, especially the rarer birds, reptiles and mammals. This has led to population declines and contributed to the loss of biodiversity in the Tonle Sap Biosphere Reserve. The cause of much of the hunting and over-exploitation that threatens the area is widespread regional poverty and a lack of food security for many people and communities.

Project description

The GEF-financed Tonle Sap Conservation Project is part of a larger project – the Tonle Sap Environmental Management Project - which also includes the ADB-Loan financed Tonle Sap Environmental Management Project, and the UNDP-Capacity 21-financed Capacity Building for Sustainable Development in the Tonle Sap region and Wildlife Conservation Society (WCS) and now UNV.

The project was designed to conserve and sustainably manage biodiversity and natural resources in Tonle Sap’s core and buffer areas and to strengthen institutional capacity at key levels such as government and local communities. Its objectives are: to support economic development and natural resources management;  to strengthen community-based natural resources management systems for rural development; and to conserve biodiversity through protection and/or sustainable use of resources.