Background: As the United Nations specialized agency with a specific mandate for science, UNESCO works to advance and promote science in the interests of peace, sustainable development and human livelihoods, in close collaboration with its Member States and a wide variety of partners, through its Man and the Biosphere Programme (MAB) and World Network of Biosphere Reserves (WNBR). Tonle Sap is the largest freshwater lake in South East Asia, covering up to 1-1.6 million ha in the wet season with 8-11 m deep. It harbours rich biological diversity and ecosystems as well as vast cultural heritage, being one of the world’s most productive inland fishing waters. Recognizing its unique ecological, economic and cultural values, Tonle Sap was inscribed on the UNESCO World Network of Biosphere Reserves in 1997, and intently enforced by Royal Decree in 2001.