The Tonle Sap is the most important inland wetland in Southeast Asia covering an area of 250,000-300,000 hectares during the dry season, and 5 to 6 times more surface during the wet season. The large wetland system supports one of the world's most productive freshwater fisheries and the ecosystem is essential to the survival of many globally significant species. Although the lake provides for a huge population, human population and development pressures are increasing and pose major threats to the Tonle Sap Lake.

The lake’s biodiversity underpins the livelihoods of much of the one quarter of the Cambodian population that lives in the five provinces that abut the lake (about 2.9 million people) and supplies up to 70% of the protein intake of Cambodia’s population as a whole. As a regional resource, the lake is the seasonal breeding, nursery, and forage grounds for fish that subsequently migrate to the Mekong River and many tributary rivers along the way; and a reservoir from which water drains in the dry season to control salinity intrusion and conserve mangroves in the Mekong Delta. It is an environmental hotspot of global significance.

Threats include overexploitation of fisheries and wildlife resources, encroachment during the dry season, and cutting of the flooded forest, leading to severe and rising levels of poverty and a pending environmental disaster. In the lakeside provinces about 38% of the population fall under the official poverty line, the highest proportion in the country.